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Ration balancing in New Zealand dairy farm management: 

A case farm simulation study 

A thesis submitted in partial fulfilment of the requirements for the degree 

of Master of Agricultural Science in Farm Management at 

Massey University 

Jose V. Uribe C. 

1995. 



Abstract 

New Zealand dairy fanners are amongst the most cost effective producers of milk in the world. 

Nevertheless the genetic potential of New Zealand cows for milk production remains substantially 

underutilised. The present relatively low milksolids production per cow is a consequence of pasture-based 

feeding systems that do not provide all of the nutrients necessary for high (>30kg/cow/day) milk 
production. A potential means to increase per cow production is to balance pasb.Ire diets to provide the 

correct quantities and ratios of nutrients to meet target levels of milksolids production. 

A review of the information available on the nutrient characteristics of feeds available in New Zealand 

for dairy cattle was completed. This indicated that most feed sources are docmnented only in very simple 

nutritional terms and generally few of the parameters necessary for ration balancing are included. Also 

regional and seasonal variation in feed quality is poorly defmed. Implementation of ration balancing 

programs on dairy farms will require the development of a more comprehensive feed database, especially 

for forages. 

The simulation model UDDER was used to investigate alternative strategies to profitably increase 

production per cow on a case study dairy fann. This analysis indicated that extending lactation by 30 days 

and supplementing pasture in early lactation with maize silage could increase milkfat yield by 17.9 kg per 

cow and the annual gross margin by $78.9 per cow. Thus there appears to be scope to profitably increase 

production per cow on the case swdy farm. However, UDDER is an energy-based model and does not 

consider the nutritional composition of the cows daily feed intake. CAMDAIRY, a computer program for 

analysing dairy cow rations, was therefore used to evaluate the nutritional adequacy of the diets "fed" to 

the cows by UDDER. This analysis suggested that the diets provided excess rmnen undegradable protein 

(RDP) and as a consequence of this milk production was likely to be overestimated by UDDER. A diet 

that provided nutrients for higher levels of milk production was then formulated. The benefits of that diet 

were calculated using a spreadsheet partial budget that considers both immediate and carry-over effects 

of supplementation on financial returns. This showed that the diet formulated by CAMDAIRY could 

increase profit by $7.93 per cow. 

It was concluded that ration balancing would be a useful aid to feed management on New Zealand dairy 
farms, but requires feed and animal monitoring systems to be put in place to determine the type(s) and 

period(s) of supplementation required. Ration balancing software such as CAMDAIRY should be used 

with caution until it has been more widely validated for New Zealand pastoral feeding systems. In 

particular this study suggests that further research on the utilisation of pasture protein is required. 

Keywords: Milk production; UDDER; CAMDAIRY; supplements; ration balancing; pasture systems. 

Title: Ration balancing in New Zealand dairy farm management A case farm simulation study. 

Author: Uribe, J.V. 1995. 



Acknowledgments 

As with anything in life there are many people who in many ways helped with 

the completion of this masterate. 

Thanks are due to my chief supervisor Professor Warren Parker for his support 

and assistance throughout this project. Dr Chris Dake and Dr Nick Edwards 

provided ideas an comments during the development of this project. Special 

thanks to Associate Professor Colin W. Holmes for his input to this project and 

throughout my studies in New Zealand. 

Thanks also to Dr Hugo Varela-Alvarez for his committed support and friendship 

and to Mr. Alastair MacDonald for his valuable help with farm data and the 

operation of UDDER. 

The New Zealand Ministry of Foreign Affairs and Trade is acknowledged for 

providing me with the opportunity to study at Massey University. 

I would also like to acknowledge all the people who in many ways contributed 

to the development of this project. 

I would like to express my gratitude to my family in Colombia for their essential 

support and motivation. Very special thanks are also due to my wife Ana Marfa 

for her patience, support, encouragement, love and sacrifice. Finally, my son Juan 

Felipe is acknowledged for all the happiness he has brought into our lives. 



Table of Contents 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . n 

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . m 

Table of contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV 

List of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vn 

List of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IX 

Chapter I Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -.  . . . . . . . I 

I . I  Ration balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

1 .2 Current New Zealand situation . . . . . . . . . . . . . . . . . . . . . . . . . 4 

1 .3 Supplements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

1 .4. Purpose and scope of the investigation. . . . . . . . . . . . . . . . . . . 7 

Chapter 2 Literature review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

2.1 Increasing pasture production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

2.1 .1 Nitrogen fertiliser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

2.1 .1 .1 Animal response to N fertiliser . . . . . . . . . . . . . . . . 1 1  

2.1 .2 Phosphate fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

2. I .3 Potassium (K), Lime and Magnesium (Mg) . . . . . . . . . . . .  I 3  

2.1 .4 Inigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

2.2 Calving and drying-off dates . . . . . . . . . . . . . . . . . . . . . . . . . 15  

2.2.1 Calving date and pattern . . . . . . . . . . . . . . . . . . . . . . . . . 15  

2.2.3 Drying-off dates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

2.3. Supplements in dairy systems . . . . . . . . . . . . . . . . . . . . . . . . 16 

2.3.1 Effects of supplements on herbage intake . . . . . . . . . . . . . 18  



V 

2.3.2 Dairy cow performance from concentrates . . . . . . . . . . . . 20 

2.3 .2.1 Milk response . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

2.3.2.2 Liveweight response . . . . . . . . . . . . . . . . . . . . . . . 24 

2.3.3 Dairy cow performance from forages . . . . . . . . . . . . . . . 25 

2.3.3 .1 Silage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  25 

2.3 .3 .2 Maize silage . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  27 

2.3 .3 .4 Hay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 

2.3 .4 Supplementary feeding and reproduction . . . . . . . . . . . . . . 29 

2.4 Ration balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1  

2.4.1 Nutritional requirements of grazing cows . . . . . . . . . . . . .  32 

2.4.2 Methods for ration balancing. . . . . . . . . . . . . . . . . . . . . . 36 

2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 

Chapter 3 New Zealand feeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 

3 .I Pastures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 

3 . 1 .1 Nutritive value of pasture . . . . . . . . . . . . . . . . . . . . . . . . .  40 

3 . 1 .2 New Zealand pastures . . . . . . . . . . . . . . . . . . . . . . . . . . .  42 

3 .2 Silage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 

3.3 Hays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 

3 .4 Straws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 

3 .5 By-products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 

3 .6 Concentrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 

3 .  7 Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 

3 .9 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 

Chapter 4 Case farm simulations with UDDER . . . . . . . . . . . . . . . . . . . 60 



Vl 

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 

4.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 

4.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 

4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 

4 .5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 

Chapter 5 Test runs with CAMDAIRY . . . . . . . . . . . . . . . . . . . . . . . .  78 

5 . 1  Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  78 

5 .2 Description of the model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 

5 .3 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 

5.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 

5 .5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 

5 .6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 

Chapter 6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 13 



List of Tables 

Table 2. 1 .  Immediate milk production responses to concentrate feeding 

of dairy cows in different countries . . . . . . . . . . . . . . . . . . . 22 

Table 2.2 Energy (E) costs of physical activities per kilogram of 

liveweight (LW) of dairy cows . . . . . . . . . . . . . . . . . . . . . . 33 

Table 3 . 1 .  Nutritional parameters of New Zealand pastures . . . . . . . . . .  43 

Table 3 .2. Nutritional parameters of New Zealand silages . . . . . . . . . . .  4 6  

Table 3.3 Nutritional parameters of New Zealand bays . . . . . . . . . . . .  48 

Table 3.4. Nutritional parameters of New Zealand straws . . . . . . . . . . .  50 

Table 3 .5. Nutritional parameters of New Zealand by-products . . . . . . .  52 

Table 3 . 6 .  Nutritional parameters of New Zealand concentrates . . . . . . . 54 

Table 3 . 7 .  Nutritional parameters of some New Zealand crops . . . . . . .  56 

Table 4.1 .  Effects of delaying drying-off dates (10, 20 and 30 days) on 

production per cow, average cow condition score, average 

pasture cover and gross margin per cow and per hectare. . . . 6 5  

Table 4.2. Effect of delaying drying-off date by 10  days and 

supplementing with meal and maize silage in early and late 

lactation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6  

Table 4.3. Effect of delaying drying-off date by 20 days and 

supplementing with meal and maize silage in early or late 

lactation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7  

Table 4.4. Effect of delaying drying-off date by 30 days and 

supplementing with meal and maize silage in early or late 

lactation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 

Table 5.1. Predicted pasture dry matter intake, change in average 

condition score and likely milk production (litres/day) during 



V1ll 

the fourth week of lactation for different nutritional 

parameters for an average year on No.4 dair y farm using 

U DDE R and CAMDAIRY . . . . . . . . . . . . . . . . . . . . . . . . . 83 

Table 5 .2. Predicted dry matter intake, change in condi tion score and 

likely milk production (litres/ day) durin g the fourt h week of 

lactation for different nutri tional parameters for strategy 

D030+MSE (feeding medi um and high quali ty maize si lage 

in early lactation) on No.4 dair y  farm usi ng U DDE R and 

CAMDAIR.Y . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . 8 5  

Table 5 .3 .  Predicted cow dry matter intake, change in cond� tion score 

and li kely milk production (li tres/ day) during the 34th week 

of lactation for dif ferent nutri tional parameters for strategy 

D030+MSL (feeding high qual ity maiz e  silage in late 

lactation) on No.4 dairy farm using U DDE R  and 

CAMDAIR.Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6  

Table 5 .4. Suitabil ity of al tern ative diets to increase milk production of 

cows in early-lactation at . No.4 dairy farm , based on a 

CAMDAIR.Y prediction of cow perform ance . . . . . . . . . . . .  8 7  

Table 5 . 5 . Probable milk production responses (lil cow/ day) predicted by 

CAMDAIR.Y for different levels of cru de protein in pastur e 

dry matte r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 9 



List of figures 

Figure 2 . 1 .  The relationship between O lsen P soil test and milk solids 

production. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

Figure 2.2. Pasture substitution rates at different pasture  intakes when 

supplementing with concentrates and fodder . . . . . . . . . . . . 19 

Figure 2 .3. Factors affecting the response of cows to supplement s . . . . .  20 

Figure 4 .1 .  E xperimental design used to evaluate effect of a ltern ative 

management options with UD DE R  . . . . . . . . . . . . . . . . . . . 64 

Figure 4 .2. Milk production curv es for an average year, dr ying-off days 

later (D030) and 0030 plus maiz e silage in early lactation . . 6 9  

Figure 4.3. Average cow condition score for an average year, drying- off 

30 days later (D030) and 0030 plus maiz e  silage in early 

lactation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9  

Figure 4 .4. Average pasture cover for an average year ,and a strategy 

with 30 days extra milk and maize silage feeding in ear ly 

lactation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1  

Figure 4 .5. Average pasture OM intake for an average year, an d  a 

strategy with 30 days extra milk and maize silage feeding in 

early lactation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 

F igure 4 . 6 .  Metaboliza ble energy intak e for an average year, and a 

strategy with 30 days extr a milk and maize silage feed ing in 

early lactation . . . . . . . . . . . . . . --. . . . . . . . . . . . . . . . . . . . 73 



Chapter 1 

Introduction 

Dair y farmers in New Zealand face some import ant farm management 

chall enges in relation to herd productivity as the twenty fir st century is 

approached. O ne of these is to develop mechanisms to profitably exploit th e  

genetic potential of New Zealand dair y cows which is presently poor ly utilised for 

milk solids (P eterson 1988). This under utili sation of herd genetic capacity reflec ts 

curr ent feedin g systems which are mai nly based on gr az ed pastures only or graz ed 

pastures plus conserved derivatives such as hay and silage. Essentially, New 

Zealand's  cows are unable to express th eii abil ity to produce mil ksolids, bec ause 

pasture- onl y diets cannot fulfill the cow's diet requir ements in terms of both 

quantity and quality during certai n  times of the year, espe ciall y when they are 

stoc ked at moderate to hi gh rates. 

The challenge to enhance the  productivity of pasture- based dairy systems 

especially applies to the " top" farmers who have reached the point of " no where 

else to go" under present systems of man agement (Bryant 1990). T hese farmers 

are achi eving per cow prod uction of 300 kg MS per lacta tion and per hectare 

prod uction of 950-1000 kg MS per year (LIC 1993) and are obtaini ng high 

(probably in th e  order of 75-85%) utilisation of ann ual pasture grown. They 

th erefore have very limited capacity to grow and utili se more pasture (Bryant 



Introduction 2 

1993). Thus, there is little scope for further improvements in production per cow 

and per hectare, through the manipulation of the key management variables in 

New Zealand dairy systems: stocking rate, calving date and grazing management. 

Balanced against these challenges is an optimistic future for the New 

Zealand dairy industry. The recent agreement on trade and tariffs (GATT) should 

reduce both subsidies and the protectionist quotas of New Zealand's main 

competitors and markets respectively (NZDB 1994 ). Under the current situation 

New Zealand has achieved a 25% share of the world market for-dairy products; 

it is thought that under the GATT agreement New Zealand dairy products will 

become even more competitively priced and attractive to buyers. Thus, it is 

expected in the medium-term that New Zealand farmers will benefit through 

higher milksolids payout. However, this will probably be mitigated to some extent 

by the strengthening value of the New Zealand dollar relative to the currencies of 

its major trading partners, increased competition from similar pasture-based 

producers in South America and Australia, and the adoption of lower cost systems 

of production in the U.S.A. mainly through economies of scale. Overall, however, 

the New Zealand dairy industry can look forward to a greater share in the 

international market and higher prices for dairy products. 

1.1 Ration balancing 

Given the outlook for the future of the New Zealand dairy industry and the 

need to improve on-farm productivity the following question can be posed. How 

can the intake and quality of a pasture diet be enhanced under grazing conditions 

in order to express more of the milksolids production potential of New Zealand 

dairy cows? 



Introduction 3 

One possible strategy is to balance the cow's pasture diet to correct for 

nutrient deficiencies. The process of providing an animal with a balanced diet for 

energy, protein, carbohydrates, vitamins and minerals is called ration balancing 

(Edwards and Parker 1994). Ration balancing, which has been used extensively 

by farmers in the Northern Hemisphere under drylot conditions, should be 

evaluated in relation to New Zealand's pastoral dairy systems. 

Pasture and drylot systems are very different; drylot farming offers a high 

degree of control over feed type and quality whereas pastoral farming is subject 

to variable pasture growth and quality and the animal can exercise greater diet 

selection under grazing conditions than with specially mixed rations. In addition 

other management and fmancial constraints are also present in the New Zealand 

dairy industry (Parker and Muller 1992). 

As stated previously, ration balancing is most likely to be considered by 

farmers which are already achieving high production per cow with cows of high 

genetic merit, high pasture production (> 18t DM!ha) and high (>80%) pasture 

utilisation. Farmers who have a lot of potential to further increase production from 

pasture, through improved management and more (or more effective use) of 

inputs, are likely to obtain greater fmancial rewards by initially exploiting these 

management alternatives (Parker and Edwards 1994). 

There are several techniques for ration balancing. These range from simple 

calculations to latest computer software. Computer software will perform the 

necessary calculations to give a diet that will provide animals with the essential 

elements for a predetermined level of production at the minimum price possible 

(Varela-Alvarez 1988). Lean (1987) suggested that ration balancing should be 



Introduction 4 

seen as a means to provide a better diet, not necessarily the optimum diet (this is 

because the cost of feed still needs to be minimised). Nutrition programs provide 

the necessary means to abbreviate calculations in balancing diets. They also 

provide easy access to a feed database (Lean 1987). 

1.2 Current New Zealand situation 

The New Zealand dairy industry is very important to the nation's economy; 

it contributed around 15% of total export earnings in 1993. Although, in terms of 

world production New Zealand produces less than 1.5% of the world's milk, it is 

a key player in the international market of dairy products supplying approximately 

25% of the total world trade (NZDB 1993). The industry has a vertically 

integrated structure which includes approximately 14,500 farms, 15 co-operatively 

owned companies and a unique marketing organization, the New Zealand Dairy 

Board. New Zealand has approximately 2.6 million cows each producing around 

259 kg milksolids per lactation. The average farm area is 74 hectares and average 

herd size is 180 cows; these values have increased steadily over the past decade 

(LIC 1994). 

New Zealand dairy farmers are world renown as "low cost" producers of 

milk. This is because feed, the major variable cost of milk production, is provided 

through grazed pasture. The principles of milk production in New Zealand are 

determined by the seasonality of pasture production, in which pasture growth is 

matched with animal requirements through the manipulation of stocking rate, 

calving date and drying-off date. Pasture utilisation is maximized through the 

manipulation of stocking rate and the timing of key physiological events (e.g. 

calving) so that changes in animal feed demand coincide with periods of pasture 



Introduction 5 

deficits and surpluses. Thus, cows calve in a concentrated period (typically eight 

weeks) during late winter-early spring. In spring, pasture quality and quantity are 

generally believed to be not limiting and can match the requirements of cows for 

an acceptable level of milk production (although well below genetic potential). In 

late spring-early summer pasture growth exceeds animal requirements and both 

pasture quality and milk production begin to decline. The typical lactation curve 

for a pasture-fed dairy cow therefore has a short (3-4 weeks) peak (i.e. poor 

persistency). In late summer-early autumn milk production reduces to 5-10 litres 

a day. Cows are dried off, normally in the latter half of the autumn, on the basis 

of pasture availability, condition score and other factors (Gray et al. 1992), 

Average lactation length for New Zealand herds has decreased from 237 to 221 

days over the last 5 years (LIC 1994). 

The relatively low productivity of New Zealand's high genetic quality cows 

under grazing conditions is a consequence of the feeding system. A variety of 

factors such as: cow management (short lactations, condition scores, size of 

replacements), pasture management factors (weeds, pests, pasture species, 

drainage, soil fertility) and climatic conditions (weather) all affect current milk 

production performance (Mackle and Bryant 1994 ). 

1.3 Supplements 

Traditionally, New Zealand dairy farmers have used supplements derived 

from pasture to overcome periods of pasture deficits. These deficits mainly occur 

in late summer and winter. Supplements commonly used are hay and silage made 

from pasture swplus to animal requirements in late spring-early summer. Brookes 

and Holmes (1988) calculated that on an annual basis 0-1.2 tonnes per hectare of 



Introduction 6 

supplements (crops, hay and silage) were fed to dairy cows on seasonal dairy 

farms in the Manawatu and South Auckland areas. Parker and Muller (1992) 

estimated that supplements (hay, silage) represented approximately 5% of the 

ration of New Zealand cows. 

Generally, supplements in New Zealand are of low quality and do not meet 

the requirements of cows for high milksolids production. Many farmers regard 

supplement quality as being less important than supplement quantity, although, 

more recently there has been growing concern amongst dairy farmers and 

extension officers about the importance of maximising the quality of supplements 

fed to dairy cows (Dairy Exporter September 1994). 

According to Lean (1987), there are several ways to increase the amount 

of feed for grazing dairy cows including: increasing pasture yields through 

fertiliser and irrigation; use of hay or silage and the use of grains or formulated 

rations. Obviously, the use of any type of supplement will depend greatly on the 

likely returns obtained from its use. 

As the New Zealand dairy industry is based on a philosophy of low cost 

milk production in which grazed pasture provides the cheapest high quality feed 

to cows (Holmes 1994), the introduction of supplementary feeding other than hay 

or silage has been seen as a threat to the viability of dairy farms. Several authors 

(Meijs and Hoeckstra ( 1984); Rogers (1985) and Mayne (1990)) have identified 

substitution rate (the reduction in pasture intake per kg supplement DM 

consumed) as the main constraint to the profitable introduction of supplementary 

feeds to grazing systems. However, little research has been conducted to look at 

supplements in terms of metabolic energy (ME) value rather than DM, (Brookes 



Introduction 7 

1993) in which case substitution rate would be less important (e.g. assuming that 

the energy value of the supplement is higher than pasture). Furthermore, New 

Zealand cows are underfed during some periods of the year especially in early 

lactation when animal requirements are high but intake is constrained by pasture 

availability. Under these conditions, substitution rate is likely to have little effect 

on the total productivity of the farm. In fact, substitution effects at this time of the 

year could be beneficial in terms of pasture productivity by helping to ensure that 

pastures are maintained in their most productive growth state. 

1.4. Purpose and scope of the investigation. 

The objectives of the present study are: 

a. To investigate the potential of ration balancing in the context of the New 

Zealand pastoral dairy farms, particularly for situations where the potential 

for further increases in milk production are limited by the "traditional" all 

pasture management system. 

b. To collate information on the nutritional characteristics of New Zealand 

feeds into a database for use in ration balancing programs. 

c. To evaluate the effects of supplementing the diet of grazing dairy cows at 

critical times of the year on milk production per cow using the simulation 

model "UDDER" for a case study dairy farm. 



Introduction 8 

d. To study available software on ration balancing and to perform runs with 

a ration balancing model (CA1IDAIRY) to determine the suitability of 

diets fed to cows on the case study farm. 

Alternative methods to improve per cow milk production of pasture-based dairy 

cows are presented in Chapter 2. In the following in Chapter information on the 

current nutritional characteristics of New Zealand feeds is discussed. The 

feasibility of some of these alternatives is evaluated in Chapters 4 and 5,  

respectively, using the dairy farm simulation model UDDER (Larcombe 1990a) 

and the ration balancing model CA1IDAIRY (Irwin and Kellaway 1991). The 

concluding chapter includes comments on the models used and an overall 

discussion of the applicability of ration balancing to pasture-based dairy farm 

systems. 



Chapter 2 

Literature review 

Several factors influence milk production from grazed pastures. Stocking 

rate, calving and drying-off dates, and grazing management are major 

determinants of milk production from New Zealand dairy farm systems. Stocking 

rate allows high pasture utilisation; calving and drying-off dates permit the 

matching of animal requirements with seasonal pasture production, and grazing 

management gives some manipulation of pasture growth to utilise feed surpluses 

and minimise feed deficits (Holmes 1993). However, under this system of milk 

production, the genetic potential of cows cannot be expressed and per cow 

production is often disappointingly low (Ulyatt and Waghom 1993). 

Options to improve production per cow while maintaining the advantages 

of a pasture-based system of production include; increasing pasture production 

through fertiliser inputs (Thomson et al. 1993), prolonging lactation length 

through the manipulation of calving and drying-off dates, and the use of strategic 

supplementation to overcome feed shortages and balance the cow's diet (Edwards 

and Parker 1994). These options are reviewed in this chapter. 



Literature Review 

2.1 Increasing pasture production 

2.1.1 Nitrogen fertiliser 

10 

In New Zealand grass-clover swards are grazed by livestock throughout the 

year, and little fertilizer nitrogen (N) is applied; nitrogen fixation by clover 

provides the N supply, but growth of the most productive pastures can be 

restricted by N deficiency at some times ( Ball et al. 1979). Leguminous herbage 

species provide the prime source of N in grassland systems where fertilizer N 

inputs are low. 

The application of nitrogenous fertilizers to New Zealand pasture may 

produce responses ranging from 5 to 18 kg extra DM per kg N applied ( C ameron 

1993). Greater responses toN are obtained when it is applied in spring to rapidly 

growing pastures on farms with early calving, high stocking rates and high pasture 

utilisation ( Bryant 1983; Thomson et al. 1991). In herds stocked at high rates and 

calved early, periods of pasture shortages often occur once winter-saved pasture 

has been grazed and spring pasture growth has not increased sufficiently to meet 

the increased demands of the herd (Bryant 1983). In these situations additional 

feed has to be obtained if milk yields are to be optimised and cow condition loss 

minimised in early lactation. Nitrogen fertiliser applications are a common method 

of increasing the amount of dry matter (DM) on the farm at this time of the year 

(O'Connor et al. 1989). 

Pasture responses to N are linear at low rates of N application, before 

reaching a maximum yield and subsequently declining at higher rates of 

application (i.e. diminishing returns occur) (Morrison 1987) . Responses to N 

reflect growing conditions and are limited by temperature and radiation, especially 



Literature Review 11 

in spring and autumn (Morrison 1987). At other times, moisture or leaf area index 

are the critical limiting factors to pasture growth. Nitrogen can be used to 

overcome periods of pasture deficits, but it will usually only increase available 

DM, rather than necessarily providing a better quality feed. Sometimes N 

applications may even decrease the nutritive value of the sward (Bryant 1983). 

Several attempts have been made to defme an economic optimum rate of 

N application but, since the value of pasture depends on its quality, utilisation and 

value of animal product, an optimum can only be defmed for a -specific system 

of management. 

2.1.1.1 Animal response to N fertiliser 

Animal response to N fertiliser can be measured in terms of milk 

production, liveweight gain and pasture saved. The response is strongly influenced 

by herbage utilisation, and hence by grazing pressure at individual grazings. 

Holmes and Wheeler (1973) reported responses in kg milksolids (MS) per 

kg N applied of between 0.26 and 0.45 at low and high stocking rates, 

respectively. Bryant ( 1983) concluded that N fertiliser consistently increased milk 

production in early lactation and estimated the response to be 0.38 kg MS/kg N 

applied. Similarly, Thomson et al. (1991) found a response of 0.56 kg MS per kg 

N when urea was applied at 40 kg Nlha in July. An extra application of 60 kg 

Nlha two months later, resulted in a total response of 1.08 kg MS per kg N. The 

MS response to the latter application was achieved through the conservation of 

additional supplementary feed. The authors concluded that early calving with N 

applied in July could be used to overcome a pasture shortage in early lactation. 



Literature Review 12 

Likewise, the management system should maximise pasture growth and fully 

utilise the additional DM for MS production, rather than follow a less efficient 

route through conservation and supplementary feeding. 

2.1.2 Phosphate fertilizer 

In New Zealand the primary role of phosphate (P) is to encourage legume 

growth, which in turn stimulates N production and pasture growth (Aglink 1983). 

Increasing levels of available P therefore increases annual pasture production, but 

a diminishing response curve is evident as described previously for N inputs. 

Thomson et al. (1993) suggested that on farms with Olsen P values of less than 

20, marked increases in dairy production would occur with increasing P fertilizer 

applications. For farms with Olsen P levels greater than 30, profitable increases 

in dairy production would only result if increased pasture production could be 

effectively utilised by an appropriate management change i.e. an increase in 

stocking rate. Thus, O'Connor et al. (1984) recommended that farms with Olsen 

P soil test values above 30 could possibly decrease or temporarily stop P 

applications, because they already have reserve P levels. 

In terms of milk production, Thomson et al. (1993) reported that the 

response to P is strongly related to stocking rate. The authors reported a response 

rate of 4.2 kg MS/ha (Figure 2.1) for each unit increase in Olsen Pranging from 

22-29 and 1 .8 kg MS/ha when Olsen P levels are greater than 30. 



Literature Review 

Increase in 
milk solids 

10 20 

13 

1.6-1.9 kg 
milk solids I kg P 

4- 10 kg milk solids I kg P 

30 40 50 60 

Olsen P soil test 

70 

Figure 2.1. The relationship between Olsen P soil test and milksolids 

production (Thomson et al. 1993). 

2.1.3 Potassium (K), Lime and Magnesium (Mg) 

Potassium has an important role on high producing dairy farms , but unlike 

P, does not build-up reserves in the soil. This means that K applications should 

be based on soil test results to avoid excess uptake or underestimation of 

requirements that can limit pasture growth (O'Connor et al. 1984). 

Thomson (1982) in a four year experiment found that lime significantly 

increased pasture growth over summer/autumn and produced corresponding 

increases in milk production. In the fmal year of the trial lime had little effect on 

pasture growth but a relatively large positive effect on milkfat. O'Connor et al. 

(1984) suggested that lime responses are very much related to soil pH. Thus, 

providing the pH is known the amount of extra pasture produced can be predicted 



Literature Review 14 

and quantified. The optimum pH is 5.9; worthwhile responses above this value are 

unlikely. In addition to rising pH, lime also elevates Ca and Mg levels (Thomson 

1982) and this may impact on milk production since both these elements are 

required by the lactating dairy cow (Wilson 1981 ). 

The application of Mg in the form of MgO will increase soil, plant and 

animals levels (O'Connor et al. 1987) . The amount of Mg applied should be 

based on soil test results for individual farms. Soil samples should be taken each 

2-3 years (O'Connor 1984). 

In general, fertiliser use will increase pasture DM production without 

altering the seasonal variation in production. The key factor in profitable fertiliser 

use (unless there is a specific deficiency) is that extra pasture DM grown is eaten 

by livestock. This usually means that a high stocking rate is desirable. If a farm 

has already a high stocking rate and pasture utilisation (>80% of pasture grown), 

the extra pasture grown could be used to improve animal intake. Despite this, high 

levels (> 350 kg MS!lactation) of production per cow are unlikely from the extra 

pasture eaten because pasture only diets cannot fulfill cow requirements for high 

levels of milk production (Muller 1993). 

2.1.4 Irrigation 

lnigation provides another strategy to increase pasture production. Water 

applications during dry summers will usually result in a considerable increase in 

pasture growth; for example the application of 600 mm water resulted in an extra 

3,200 kg DM/Ha being grown annually in two dry summers in the Manawatu 

(Holmes and MacMillan 1982). Water supply affects seasonal growth patterns as 



Literature Review 15 

well as annual yields. There is no doubt that, on average, irrigation will reduce 

the seasonal variability in pasture growth and improve pasture quality during 

periods of moisture stress, but its economic feasibility is questionable in most 

localities (Leaver 1985a). The irrigation system should be able to supply 12-25 

mm of water at each irrigation interval. 

2.2 Calving and drying-off dates 

2.2.1 Calving date and pattern 

A seasonal calving pattern mmnmses milk production costs m New 

Zealand, because it allows the herd's feed requirements to be matched with the 

supply of grazeable pasture throughout the year. This is the main reason why 95% 

of New Zealand herds calve in the spring in a concentrated pattern (MacMillan 

et al. 1990). Calving is planned to commence in late winter, with a large 

proportion (approximately 75%) of cows entering the herd during the following 

4 weeks and the remainder over the next 6-12 weeks (MacMillan 1984a). Thus, 

the concentrated seasonal calving pattern in New Zealand attempts to; maximize 

utilisation of pasture DM in situ, limit conservation of pasture as hay or silage, 

and minimise cropping and the use of high energy or protein supplements 

(MacMillan 1984a). 

Calving date influences both the cow's level of feeding in early lactation 

and her lactation length (Holmes and Wilson 1987), and these two factors 

influence lactation yield. Lactation length is defmed by calving date and drying­

off date; while the level of feeding in early lactation is strongly associated with 

total milk yield per lactation (Bryant and Trigg 1982). 



Literature Review 16 

A herd's calving pattern primarily reflects the conception pattern during the 

previous seasons breeding programme (MacMillan 1984b ). High submission rates 

and conception rates should reduce the fmal empty rate and the proportion of 

cows which may need to be induced (Hughes 1984). This will also increase the 

average number of days in milk for the herd, and concentrate labour requirements 

because rearing calves, oestrus detection, mating and calving will all occur over 

a relatively short time period (Holmes and Wilson 1987). 

2.2.3 Drying-off dates 

Drying-off date is an important element of pasture and animal management 

in New Zealand a dairy farm systems (Gray et al. 1992). Drying-off date must be 

set to achieve the following objectives; an adequate period of rest to allow the 

mammary tissues to prepare for the next lactation, an increase (or maintenance of) 

the amount of pasture on the farm and increase (or maintenance) of cow body 

condition score (Bryant 1 984). Discontinuing milk allows the herd's feed 

requirements to be reduced suddenly and significantly. Prolonging lactation length 

will produce more milk in the present lactation but may prejudice the next 

lactation's production and increase feed costs (Holmes 1990; Gray et al. 1 992). 

This effect can be profitably overcome by supplementing cows in late lactation 

(Holmes et al. 1994 ). 

2.3. Supplements in dairy systems 

The output of milk from pasture depends upon the combined effects of 

pasture grown and the efficiencies with which pasture is harvested and converted 

into milk by the grazing cow (Holmes 1990). High stocking rates and low daily 



Literature Review 17 

herbage allowances, which are typically associated with efficient pasture 

utilisation, impose limitations on dairy cow performance from grazed herbage. 

Likewise, the seasonal pattern of pasture growth, and changes in pasture quality, 

also limit milk production from pasture. Supplementary feeding is therefore 

necessary at certain times of the year if consistent and high (> 30 litres day) 

levels of milk production from pasture are to be achieved (Leaver 1985a; Muller 

1993). Supplementation of grazing animals is normally undertaken to; supply 

nutrients that are deficient in the cow's diet because of either low quality or 

quantity of the pasture available for grazing (Stockdale and Trigg 1989), increase 

total daily intake (Rogers 1985, Leaver 1985b, Grainger and Mathews 1989) or 

improve animal performance over that which can be produced from pasture alone 

(Mayne 1990). Likewise, Lean (1987) suggested that the provision of 

supplementary feed reduces the variation in annual income and may increase 

income levels, depending on the type, cost and effectiveness of the extra feed 

inputs. 

The supplements provided to the animal may be classified into three 

general groups: (1) Energy supplements; (2) protein supplements; (3) inorganic 

nutrients (minerals and vitamins) (Allden 1981). In general, it is believed that 

energy supplements play the most important role under temperate pasture grazing 

conditions because a diet with adequate energy usually has acceptable levels of 

protein, minerals and vitamins. There are, however, some exceptions to this such 

as diets for animals in an active growing state or lactating cows with high genetic 

potential for milk production. 



Literature Review 1 8  

2.3.1 Effects of supplements on herbage intake 

Including supplementary feeds (concentrates and forages) in the diet of 

grazing animals may increase total DM intake and organic matter digestibility but 

reduce the intake of pasture DM. This is called the substitution effect (Hodgson 

1 990). Substitution rate (decrease in pasture intake per kg supplement eaten) is 

mainly affected by the level of pasture on offer (Meijs and Hoekstra 1984) and 

the quantity and type of supplement provided (Rogers 1985). 

Grainger and Matthews (1989) suggested a significant interaction between 

supplementation and pasture allowance for daily pasture intake. They observed a 

linear relationship between herbage allowance and substitution rate that was 

highly significant despite differences in pasture digestibility of 580 to 800 glkg 

DM, pasture mass ranging from 2.3 to 5.5 t DM!ha and milk yields varying from 

10  to 25 Ucow day. However, this relationship may not be present at pasture 

masses below 2000 kg DM/ha where intake is limited independent of pasture 

allowance (Holmes 1987). At high herbage allowances pasture substitution for 

supplement is high; this is mainly associated with a reduction in grazing time 

(Mayne 1 990) rather than the rate of biting or bite size (Leaver 1 985b). The effect 

of substitution rate on pasture intake can be seen in Figure 2.2. When pasture on 

offer is in the range of 6-12 kg DM/cow day, substitution rates for hay and silage 

are higher than for concentrates (Grainger 1991). As a result of substitution 

animals cannot maximise their intake of pasture when supplements are provided 

but if the quality of the supplement is higher than that of the pasture, total 

metabolizable energy intakes and the "balance" of the diet can be expected to 

improve. Thus, supplement type influences substitution rate; in the case of 

concentrates Rogers (1985) suggested a substitution rate effect of ( 65%) for 



Literature Review 19  

energy supplements and (30%) for protein supplements. Substitution rate effects 

also may partly be related to the difference between the intake of nutrients from 

herbage and the cow's  daily nutrient requirements. When this difference is 

negative (e.g. at a low herbage allowance) the substitution of herbage is low; 

when the balance is positive the substitution of herbage is high (Meijs and 

Hoekstra 1984 ) . Other factors affecting substitution rate are pasture digestibility, 

season of the year and yield potential of the animal (Mayne 1990). 

Figure 2.2. Pasture substitution rates at different pasture intakes when 

supplementing with concentrates (•) and fodder (*) (Grainger 1991). 



Literature Review 20 

In New Zealand low herbage allowances and high stocking rates are 

common, and under these conditions substitution rate would be of less importance 

if supplementation was implemented (Phillips 1994 ) . 

2.3.2 Dairy cow performance from concentrates 

2.3.2.1 Milk response 

A large number of factors affect the response of cows to supplementary 

feeding Figure 2.3 . Each of the factors identified interact with each other and not 

only affect the immediate response to the supplement but also subsequent 

production. Predicting the result of supplementary feeding is therefore complex. 

S ta g e  o f  
la c t a t i o n  

L e v e !  o f  
p r o c u c t i o r. 

l 

A m o u n t  o f  I / 
c o n c e n tr a t e T / 

......------� 

C c w  
c o n d i t ion 

� � M I L K  
I R E S P O N S E  

Q u a li ty . o f  +-­
c o n c e ntra t e  

A m o un t  o f / 
p a s tur e 

� Q u a lity o f  

p a s ture 

Figure 2.3. Factors affecting the response of cows to supplements (Rogers 

1985). 



Literature Review 21 

Leaver (1985b) suggested that an improvement in the nutritional status of 

an animal through supplementation may lead to greater productivity during the 

feeding period (i.e. an "immediate response") or a change on production potential 

after supplementary feeding has ended (i.e. a "residual response" or carry-over 

effect). The carry-over effect can be represented through a continued increase in 

milk yield, an improved condition score or/and increase in average pasture cover 

(Kellaway and Porta 1993),  or by changes in lactation associated with herd 

reproductive performance. Therefore, the cumulative carry-over effect of 

concentrates will almost always be greater than the immediate .effect on milk 

production (Lean 1987). 

The immediate response of grazing dairy cows to concentrates reported by 

different authors in different countries is summarized in Table 2. 1 .  The responses 

are extremely variable, depending on the factors shown in Figure 2.3. For 

example, the response reported by Meijs (1985) was obtained with high fibre 

concentrates. The high responses obtained by Le Du and Newberry ( 1981)  were 

obtained by supplementing grazing dairy cows for 4 weeks at a low herbage 

allowance. The same authors reported overall responses ranging from 2.9 to 3.5 

kg milk/kg concentrates fed. The limited data from New Zealand is from 

experiments carried out in the late 50s, early 60s with cows of lower genetic merit 

(Bryant and Trigg 1982). The responses obtained by Taylor and Leaver (1984a) 

were with stall fed cows, and responses under grazing conditions could be 

expected to be different mainly because of diet selection. 

Rogers (1985) reviewed the use of pasture and supplements for dairy cows 

m the temperate zones and calculated an average "immediate" response to 

concentrate supplements of 0.5 litres extra milk/kg concentrate eaten, the response 



Literature Review 22 

ranged from 0 to 0.9 1/k.g; the total response averaged 1 . 1  l!kg concentrate fed. 

While Lean (1987) suggested that the total milk response to concentrate feeding 

can be up to 1 .2 kg milk/kg concentrate fed. Rogers et al. (1983) concluded that 

the economic value of the response depends very largely on the "carry-over" 

effect which is very variable. 

Table 2.1. Immediate milk production responses to concentrate feeding of 

dairy cows in different countries. 

Reference Milk Units of response Supplement Country 

response type 

Meijs ( 1985) 1 .3 kg milk/kg cone. Concentrate Holland 

Gleeson ( 1981) 1 - 1 .78 kg milk/kg cone. Concentrate Ireland 

Le Du & Newberry ( 1981)  1-1 .9 kg milk/kg cone. Concentrate UK 

Tay1or & Leaver (1984a) 0.5-1 .6 kg milk/kg cone. Concentrate UK 

Bryant & Trigg ( 1982) -0. 17-1 .39 kg milk/kg DM Various supp. Australi�Z 

Rogers ( 1985) 0.0-0.9 kg milk/kg cone. Concentrate Australia 

Stage of lactation has a major influence on the response of grazing dairy 

cows to high energy supplements. Cows tend to direct more energy towards milk 

production in early lactation, but in the last third of lactation a greater proportion 

of energy intake is directed towards body weight gain (Broster and Thomas 1981). 

This effect was confirmed by Stockdale et al. (1987) who found decreased milk 

responses to concentrate feeding as lactation progressed. Stockdale and Trigg 

(1989) also looked at interactions between stage of lactation and pasture 

allowance and found responses of 1 .85, 0.053 and 0.059 kg milk, milkfat and 



Literature Review 23 

milk protein, respectively, from feeding an additional kg DM to cows fed 6.8 kg 

DM of pasture per day in early lactation; the authors suggested that if the cows 

were fed 1 1 .7 kg DM of pasture, marginal responses from concentrates would be 

more than halved. 

Cow condition score affects the milk response to supplementary 

concentrates, particularly when supplementary feeding begins. Cows in low 

condition score in early lactation direct more energy to body weight than to milk 

production when supplemented (Grainger et al. 1982). Greater responses to 

supplementary feeding in early lactation can therefore be expected from cows at 

an optimum (> 4.5 units) condition score (Kellaway and Porta 1 993). Because of 

this energy partitioning effect, Stockdale et al. (1990) showed that concentrate and 

pasture quality combine together and determine the magnitude of the milk 

response. In their experiments cows were fed high and low quality pasture 

supplemented with wheat and high energy pellets. The cows fed high quality 

pasture obtained similar milk responses for both supplements, while the response 

for cows fed low quality pasture favoured the high energy pellets . This was 

probably because the pellets provided a more balanced diet. Thus, balancing the 

diet of cows fed high quality pastures can be challenging; sometimes it requires 

the correction of deficiencies (fibre) (Kellaway and Porta 1993) or excesses 

(rumen degradable protein) (Muller 1993). 

Cow genetic merit can influence the milk response to supplementary 

feeding. High breeding index cows direct more energy to milk production and 

lose more weight in early lactation than low breeding index cows (Wilson and 

Davey 1982). More efficient responses can therefore be expected in herds of high, 

rather than low, genetic merit 



Literature Review 24 

The level of concentrate in the diet has significant implications on the milk 

response in grazing dairy cows. A progressive reduction in the response occurs 

as the level of energy increases in the diet because a greater proportion of energy 

is directed to body condition score rather than milk production. In addition, other 

nutrients can become deficient as the proportion of high energy supplement in the 

diet is increased (Kellaway and Porta 1993). 

In summary, concentrates fed to grazing dairy cattle will · increase the 

amount of milk yield, but the extent of this increase will depend on factors such 

as stage of lactation, level of pasture allowance and the herd' s  genetic potential 

(individual cow feeding is normally not an option under grazing conditions). In 

addition, other factors such as concentrate type may affect the herd's response to 

supplementary feeds. It is important to highlight that all of the factors discussed 

above interact with each other and the overall milk production response will 

reflect their combined effect. 

2.3.2.2 Liveweight response 

An increase in body condition score of lactating grazing dairy cows after 

being fed supplements is usually classified as a carry-over effect The liveweight 

response to concentrate supplementation is highly dependant on cow condition at 

the time of supplementation. Cowan et al. (1977), working with four groups of 

Friesian cows grazing tropical pastures (Panicum maximum) fed 0, 2, 4 and 6 

kg/cow day respectively of a maize soybean concentrate, found that concentrate 

feeding markedly affected the liveweight of cows at drying-off; cows being fed 

4 or 6 kg/cow day were 50 kg/cow heavier on average than cows fed the lower 



Literature Review 25 

rate. Similarly, Bryant and Trigg (1982) found that liveweight loss in cows in 

early lactation was reduced by 150 g per kg of supplement DM offered. 

It can be concluded that when supplemented cows are achieving a high DM 

intake either reduced liveweight loss or increased liveweight gain can be expected. 

However, the extent of these changes will depend on factors such as cow 

condition score and stage of lactation (energy requirements), and the partitioning 

of nutrients towards milk production or liveweight gain. 

2.3.3 Dairy cow performance from forages 

Forages may be used to supplement grazing animals particularly when 

herbage is in short supply. They are usually less expensive than concentrates and 

can be used as a buffer to pasture (Leaver 1985a). The degree of benefit from 

forage supplementation will depend on the quality of the forage, the timing of 

feeding and the herbage allowance provided for grazing (Phillips and Leaver 

1985a). Feeding conserved forage as a supplement to grazing cows when herbage 

quality is low or during feed shortages, generally results in increased total DM 

intake and improvements in animal performance (Phillips 1988). 

2.3.3.1 Silage 

Offering grass silage as a buffer feed when herbage allowance is restricted 

leads to increases in total DM intake (Phillips and Leaver 1985b). However, the 

voluntary intake of silage is normally lower than that of the fresh material from 

which it is made. The extent of this depression can be correlated with silage 

quality (Gordon 1989). Thus, when silage is of lower or similar quality to 



Literature Review 26 

herbage, inclusion of silage in the diet generally results in a depression in milk 

yield relative to ad libitum herbage (Phillips 1988). 

Feeding of medium quality silage (70% DM digestibility) to New Zealand 

cows in early lactation during 30 days had immediate effects on milk yield and 

miJksolids production (Clark 1993). A total response of 26 g MS per kg DM 

silage was obtained in the experiment; the milk of cows fed silage had slightly 

lower milkfat (4.4%) and milk protein content (3 .4%) than the control group. 

Phillips and Leaver (1985b) suggested that supplementation of herbage with silage 

increased rumination times, due to an increase in fibre intake. This resulted in 

lower milk yields but considerably higher milkfat content. Heifers in mid-lactation 

had higher intakes when silage was offered but the extra energy was partitioned 

towards liveweight gain in a study by Phillips and Leaver (1985b). However, 

milkfat yields were increased by offering silage, probably as a . result of the extra 

energy and fibre intake. 

The effects of inclusion of silage on the fat content of the milk are varied 

but tend to be inversely related to the effect on milk yield. Where silage is of 

better quality than herbage, fat content is decreased. Milk protein content tends 

to be reduced by including silage in the diet. This could arise from either a 

reduction in total energy intake or the low protein content and nitrogen retention 

of silage compared with fresh herbage or both (Phillips 1988, Gordon 1989). 

Carry-over responses to pasture silage include increased average pasture 

cover and increased animal liveweight. In the long term silage may enable a 

higher stocking rate to be maintained (Phillips and Leaver 1985b). This was 

coninm.ed by Clark (1993), who found an increase in farm cover of 490 kg 



Literature Review 27 

DM!ha on the farmlet where cows had been supplemented with pasture compared 

with that of the control farmlet. 

In summary, offering pasture silage to grazing dairy cows can result in 

different short term responses. The extent of these responses will mainly depend 

upon the quality of the silage on offer, but the interaction of other factors such as 

herbage allowance, cow genetic merit and stage of lactation will also affect the 

response obtained. 

2.3.3.2 Maize silage 

Inclusion of maize silage in the diet of grazing dairy cows can buffer 

variation in herbage intake and increase milk output per hectare (Phillips 1988). 

Usually, high quality maize silage has a high energy content and low crude 

protein, mineral and vitamin concentrations (see Table 3 .2). It is also quite 

fermentable and has a relatively low DM cost (Lean 1987). These characteristics 

make maize silage a suitable supplement for dairy cows grazing high quality 

pastures (Satter et al. 1992). Supplementation of grazing dairy cows with maize 

silage at up to 33% of the diet generally increases total DM intake (Hutton and 

Douglas 1975), although substitution rates can be high, ranging from 0.47 to 1 .40 

(kg pasture DM per kg silage DM) depending mainly on herbage allowance 

(Phillips 1988). 

The average milk production response to maize silage supplementation of 

pastures is 0.9 litres of milk per kg DM of maize silage eaten (Stockdale 1991). 

However, milk production responses to maize silage are variable. Generally, they 

are positive when maize silage is fed at low herbage allowances (Hutton . and 



Literature Review 28 

Douglas 1 975) or when maize silage is supplemented with rumen undegradable 

protein (e.g. meat meal) (Davison et al. 1982). Recently, Moran and Stockdale 

(1992) found positive, but not significant, milk and animal intake responses when 

cows grazing perennial pastures were supplemented with maize silage in early 

lactation. 

Leaver (1985a) suggested that if maize silage is offered ad libitum it may 

be eaten in preference to grazed herbage. However offering maize silage for short 

periods once or twice daily may lead to increases in milk yield and liveweight 

gain (Mayne 1990). 

In summary, maize silage appears to have potential for much greater use 

as a supplement for grazing dairy cows under New Zealand conditions. High 

energy maize silage may promote utilisation of pasture protein by encouraging 

microbial growth and hence increase the amount of amino acids reaching the 

small intestine (Satter et al. 1 992), and improve rumen efficiency. In other words 

supplementing ryegrass-clover pastures with maize silage should help to provide 

a more balanced diet for pasture-fed dairy cows. 

2.3.3.4 Hay 

Animal response to hay · supplementation is strongly influenced by its 

quality. In New Zealand bays are generally of low quality (See Table 3.3). Rogers 

(1985) reported that hay fed as a supplement to restricted pasture in early lactation 

gave 9 g. milkfat directly and 23 g. milkfat over the whole lactation per kg of hay 

fed. Generally, cows could not consume sufficient hay to meet energy 

requirements due to its low . digestibility limiting intake and digestion. When 



Literature Review 29 

herbage allowance is restricted, offering hay increases the yields of milk, fat, 

protein and lactose, but milkfat content may be depressed (Leaver 1985a). 

Hay is used mainly in New Zealand to maintain cow condition prior to 

calving while pasture is saved for early lactation (Holmes and Wilson 1987), 

although, some farmers also feed hay in early lactation to provide fibre to cows 

fed on lush leafy spring pasture. This practice was supported by Leaver (1985b), 

who suggested that hay can be used to increase the fibre intake of grazing dairy 

cows in spring but intakes are low unless access to herbage is limited either in 

quantity or by time. 

2.3.4 Supplementary feeding and reproduction 

Cow condition at calving and the level of feeding after calving both 

significantly effect the post-partum anoestrum interval (Rogers 1985). Moreover, 

condition score at mating, which is mainly affected by condition score at calving 

and feeding level between calving and mating, is closely related to conception rate 

(Haresign 1979). Post-partum nutrition has little effect on the reproductive activity 

of cows in good condition at calving, but a marked influence on oestrus 90 days 

post-partum in cows poorly fed prior to calving (Haresign 1979). The energy 

balance of the cows around the time of mating may also have a significant effect 

on conception rate; cows which are losing weight at the time of mating are less 

likely to conceive than those gaining weight (Butler and Smith 1987). 

When pasture is limiting, the requirement for supplementary feeding will 

be considerably reduced if cows are at an appropriate condition score at calving 

(Rogers 1985). In New Zealand, McDougall (1993) concluded that low condition 



Literature Review 30 

score at calving and at the start of mating was associated with anoestrus and 

estimated that for each unit decrease in condition score at calving the interval 

from calving to first oestrus increased by about 8 days. Loss of one condition 

score after calving only increased the interval from calving to first oestrus by 

about four days. Thus, condition score at calving appears to be more important 

than the maintenance of condition score after calving. 

Taylor and Leaver (1984b), working with cows fed high and low quality 

silage, found that calving intervals for the cows fed with high quality silage were 

significantly lower than those offered low quality silage. The authors attributed 

this effect to poor conception rates since days to frrst service were similar for both 

treatments. 

Conception rate and reproductive efficiency are reduced as a result of high 

crude protein intake (Elrod and Butler 1993). High crude protein intake results in 

elevated levels of urea in the blood, milk and tissue fluids which include uterine 

secretions and vaginal mucus. These secretions may reduce sperm viability and 

reduced embryo survival. Hence, high intake of degradable protein . supplements 

(e.g. soya bean meal) could adversely affect the reproductive performance of dairy 

cows, especially if they are already grazing high quality pastures (Williamson and 

Femandez-Baca 1992). In New Zealand, this effect was conimned by Moller et 

al. (1993) who found high blood urea levels in herds with an anoestrus problem, 

especially around the time of mating. Similarly, Elrod and Butler (1993) found 

reduced conception rates in heifers fed high degradable protein diets. 

There are consistent reports of an association between increased 

bodyweight loss and reduced fertility (Lean 1991). From a review of trials, he 



Literature Review 3 1  

estimated that for each 0. 1 kg of bodyweight gain per day, which a cow achieved 

above average, calving to conception interval was reduced by 21 days. Workers 

in USA, Australia and the UK have found very significant reproductive responses 

to increased body score at calving time. The responses to increased body 

condition score have not yet been fully defmed but will probably be curvilinear 

with diminishing returns above a condition score of 6 units (Lean 1 991 ). 

Generally, this situation is unlikely to happen under grazing conditions. 

Feeding the grazing dairy cow during the dry period to gain weight is a 

practice that can be worthwhile and in some circumstances the supplementary 

feeding of dry stock may be warranted because cow condition score at calving can 

determine productive and reproductive performance after calving (Grainger and 

McGowan 1 982). 

The preceding discussion indicates that the reproductive performance of the 

dairy cow is influenced by a very large number of interacting factors. These 

include animal, human or management, and environmental factors. In relation to 

the animal, factors such as hormonal and health status, metabolic, mineral and 

condition score are of importance. The role of supplements in the improvement 

of the reproductive performance of grazing dairy cows is mainJy related to 

decreased liveweight loss in early lactation. They may also decrease the amount 

of RDP in the diet and help to improve overall herd reproductive performance. 

2.4 Ration balancing 

Ration balancing is the process of formulating animaJ diets to provide an 

adequate quantity of energy, protein, minerals and vitamins to achieve a desired 



Literature Review 32 

level of production (Muller 1 993b). Ration balancing involves both the 

determination of an optimum diet for a particular situation and the evaluation of 

the nutrient composition of available feeds (Owen 1 983). A ration balancing 

program should therefore include information on the nutritional requirements of 

the animal and expected DM intake (VandeHaar and Black 1 99 1 )  and the nutritive 

value and costs of available feeds (Varela-Alvarez 1 988).  

Ration balancing programmes calculate the animal requirements based on 

the information provided by the user. This information generally includes average 

milk production, lactation stage, average dry matter intake, average age of the 

cows (lactation number), average body weight, average condition score and 

average peak milk yield (VandeHaar and Black 1 99 1 ;  Muller 1 992). Of these 

variables average DM intake is the most difficult factor to estimate under grazing 

conditions because of the variation in pasture quality and cow selection (Muller 

1 993 a; Edwards et al. 1 994). The correct estimation of total ration and pasture 

DM intake is one of the key issues in balancing the diet of cows grazing pastures 

(Muller and Holden 1 994). In a recent study Hoffman et al. ( 1 993) concluded that 

any ration balancing program of grazing dairy cows should include the regular 

monitoring of pasture quality to allow reformulation of the diet according to 

pasture characteristics. In their experiment this option resulted in the most 

profitable supplementation option. 

2.4.1 Nutritional requirements of grazing cows 

In New Zealand the nutritional requirements of dairy cows, and the feeds 

that they could potentially consume, are based on the metabolizable energy system 

(ARC 1980). Under this system animal requirements are expressed in terms of 



Literature Review 33 

energy, protein, minerals and vitamins. Animal energy requirements are divided 

into production (pregnancy, milk production and liveweight gain) and maintenance 

(Geenty and Rattray 1987). Energy requirements for the maintenance of grazing 

animals can vary widely with animal size, age, quality of diet, availability of 

pasture, terrain, climate, physiological state of the animal and muscular activity. 

Grazing activity increases the maintenance requirements of dairy cows relative to 

those under commed feeding conditions (Table 2.2). 

Table 2.2 Energy (E) costs of physical activities per kilogram of liveweight 

(LW) of dairy cows. (Source: CSIRO 1990). 

ACTIVITY 

Standing (compared with lying) 

Changing body position (Standing and lying) 

Walking (Horizontal component) 

Walking (Vertical component) 

Eating (Prehension and chewing) 

Ruminating 

E cost /kg LW 

10  kj/d 

0.26 kj 

2.6 kjlkm 

28 kjlkm 

2.5 kj/h 

2.0 kj/k 

Energy requirements for liveweight gain are mainly influenced by the 

nature of the gain, but factors like sex, age and physiological state are also 

important (ARC 1980). While those for pregnancy depend mainly upon the energy 

contained in the growing foetus and increase exponentially during the last third 

of pregnancy (McDonald et al. 1988). 

Milk is produced from energy obtained either directly from the feed or 

indirectly by the mobilisation of body reserves. The energy required for milk 

synthesis is main1y influenced by milk composition and varies within and between 

breeds (Holmes and Wilson 1987). Under grazing conditions cow energy intake 



Literature Review 34 

limits milk production (Kellaway 1992). Alternative feeding practices to overcome 

this deficiency and balance the diet of grazing dairy cows include supplementary 

feeding of cereal grains (Kellaway 1992; Muller 1993b), including those 

containing additional long chain fatty acids (King et al. 1990), or feeding high 

quality maize silage (Satter et al. 1992). 

The protein requirements of grazing animals are more complex than for 

energy. Fresh forages contain high quantities of crude protein (CP) and about 70% 

of this is broken down by micro-organisms in the rumen (i.e. (RDP) rumen 

degradable protein). The balance escapes (i.e. escape, by-pass or (UDP) 

undegradable protein) to the small intestine, for digestion and absorption. Rumen 

micro-organisms are capable of synthesizing all the essential amino acids either 

from plant protein or non-protein nitrogen (Leng and Nolan 1984). The supply of 

amino acids to the small intestine comes from UDP and the microbial protein 

synthesized from RDP. The amount of microbial protein depends greatly on the 

energy available and on the supply of minerals, especially sulphur (W aghom and 

Barry 1987). ARC (1980) assume that for each MJ of dietary :ME consumed the 

maximum amount of RDP that can be incorporated into microbial protein is 8.4 

g. The UDP requirements of tissue represent the difference between the net tissue 

protein requirements (Ptissue) and that supplied from microbial protein 

(RDPtissue). In this sense, the total protein requirements (Total P) are RDPreq + 

UDPreq. CAMDAIRY uses a modification of ARC (1980) to calculate the protein 

requirements of cows (Hulme et al. 1986). The high CP content of ryegrass-clover 

pastures (Table 3.1 )  and its high degradability may limit the amount of UDP 

reaching the small intestine (Satter et al. 1992). The inclusion of small amounts 

of UDP in the diet of grazing dairy cows may provide an improved amino acid 

profile reaching the small intestine and hence improve milk production per cow 



Literature Review 35 

(Muller 1993b). The inclusion of low levels of fish meal (0.8 kg) in the 

supplement of cows fed high quality pasture silage produced large milk responses 

at low (0.8 kg supplement per cow day) and medium (4 kg supplement per cow 

day) levels of supplementation (Gordon and Small 1 990). Finally, Mayne ( 1993) 

concluded that the milk production response to the inclusion of UDP in the 

supplements of lactating dairy cows fed pasture silage is mainly affected by level 

and type of the protein supplement and by variations in silage quality. 

Minerals are essential for maintaining an adequate state of production. 

Minerals are divided into macrominerals and trace minerals depending in the 

amount required in the diet (Church and Pond 1988). High producing dairy cows 

usually require supplementation with calcium and phosphorus, because they have 

a large concentration of these elements in milk (ARC 1980). The mineral status 

of dairy feeds should be monitored to avoid mineral deficiencies that can limit 

high levels of production. In CAMDAIRY constraints can be set for calcium and 

phosphorus in the diet to achieve target levels of production. If the mineral 

content of the planned diet is less than the recommended level a mineral premix 

(or other appropriate mineral source) can be included to overcome the deficiency. 

Vitamins are required to perform specific metabolic functions. Water 

soluble vitamins {B, C) requirements are met by rumen micro-organisms (Church 

and Pond 1988). Fat soluble vitamins (A, D, E) requirements must be met by the 

diet. Usually, mineral premix is formulated with vitamins to overcome possible 

deficiencies. 



Literature Review 36 

2.4.2 Methods for ration balancing. 

Ration balancing methods range from simple basic calculations (Pears on's 

square, simultaneous equations) to advanced computer software (Varela-Alvarez 

1988). In the case of modem computer software, like "CAMDAIRY", the 

calculations are performed using a linear programming (LP) algorithm. The use 

of LP allows diets to be formulated relative to objectives, least cost formulation 

and maximum profit, and subject to specific nutritional requirements for target 

levels of production. 

The least cost option results in the formulation of a diet from specific feed 

sources that fulfils energy, protein and mineral requirements at a minimum cost 

(Hulme et al. 1986). As feed (direct and indirect) is usually the largest production 

cost (50-60% ), the least cost option is mainly used by feed manufacturers to 

ensure that nutrient requirements are provided at the minimum cost (Lean 1987). 

The maximum profit formulation option aims to maximize income (V arela­

Alvarez 1988). This method considers feeds cost as an expense and milk 

production as income. The LP is used to maximize income while satisfying 

animal requirements. It is essential to know maximum dry matter intake, feed 

costs, feed composition and the milk production response to nutrients for models 

of this type. 

A more recent approach to ration balancing (Lara 1993) uses multiple 

objective fractional programming to include several objective functions. The 

advantage of this approach over traditional least cost formulation is that it allows 

the introduction of a second objective (i.e. maximisation of the inclusion of 



Literature Review 37 

specific feeds) which permits a diet that fulfils all the requirements for a specific 

level of production. 

2.5 Summary 

A number of options are available to increase per cow performance from 

grazing systems. Nitrogen fertiliser can provide a rapid method to improve overall 

animal DM intake, but it does not necessarily enhance pasture · quality and 

responses are subject to environmental conditions at and following applications. 

The use of fertilisers such as phosphate, lime or potassium provide a long term 

investment in the overall fertility of the soils and therefore result in increased 

annual pasture production. However, pasture growth responses under this strategy 

take time and do not mitigate the inherent limitations of pasture quality (although 

changes in sward composition induced by improved soil fertility may increase the 

nutritive value of pasture). 

The time of calving and drying-off date is an important determinant of 

production per cow, because in a pasture-based system, it directly affects early 

lactation feeding and lactation length. Extending lactation length normally results 

in higher milk production at the expense of condition score and average pasture 

cover. Management strategies must be developed to overcome this. This is 

discussed more fully in Chapter· 4. 

Supplementary feeding of grazing dairy cows may overcome the nutritional 

deficiencies of pastures and improve their reproductive performance. However, 

animal responses to supplementary feeding are influenced by a range of factors 

such as supplement type, supplement quality, stage of lactation, cow condition and 



Literature Review 38 

pasture quality. In addition, cows may substitute supplements for pasture and this 

effect can decrease the economic response to supplements. 

Ration balancing provides an opportunity to improve the quantity and 

quality of the diet of grazing dairy cows. However, the implementation of ration 

balancing for grazing dairy cows is presently limited by factors such as the 

estimation of cow's  intake and determination of pasture quality. In the next 

Chapter feed quality data, including that for pasture, are presented� 



Chapter 3 

New Zealand feeds 

In pasture-only dairy systems, such as those which predominate in New 

Zealand, grazed pastures must supply the animal's requirements for maintenance, 

milk production and pregnancy. Cows graze pastures all year round and hence 

their ability to express their genetic potential will reflect both the quality of 

pasture on offer and the grazing management system used. However, it is known 

that pastures cannot fulfill the cow's requirements for high (>30kg/day) milk 

production (Ulyatt and Waghom .1993). Furthermore, the nutrients available to the 

animal from pastures are more variable than those provided through a drylot 

system where feed types can be adjusted to ensure a uniform diet through time. 

The aim of this chapter is to present an overview of the quality parameters 

of feeds available in New Zealand and to identify the nutritional information of 

pastures and feeds required for ration balancing. 



New Zealand feeds 40 

3.1 Pastures 

Forages such as pastures are an essential part in ruminant feeding and in 

achieving a balanced ration (Muller 1993a). Although pastures are the main 

source of feed supply for dairy cows in New Zealand, published information 

regarding their nutritional value is scarce (Edwards and Parker 1 994 ). This also 

applies to other potential sources of dairy feeds. Where information is available 

on pasture quality the data usually covers only a limited range of parameters such 

as DM, digestibility, crude protein, metabolizable energy and some minerals. In 

many cases only the first two factors have been measured. This lack of 

information can partially be attributed to the fact that in grazing situations, pasture 

quality determinations are complicated because pasture is a highly variable feed 

source and can even change on a daily basis (Wilson and Moller 1993). 

3.1.1 Nutritive value of pasture. 

The feeding value of pasture under grazing conditions has primarily been 

considered as the potential of herbage to supply energy to the animal, although 

under certain conditions other nutrients including protein, minerals and vitamins 

may be limiting. Nutritive value is the concentration of nutrients in a feed and is 

dependent on the digestibility of the feed and the efficiency with which the 

digested nutrients are converted to animal products (Ulyatt 1981). Paterson et al. 

(1994) suggested that the two main factors determining forage quality are forage 

intake and digestibility. Ultimately, the performance of the animal is the true 

indicator of forage quality. 



New Zealand feeds 41 

Maturation affects the nutritive value of pasture. Several changes occur 

during the process of plant maturation; structural carbohydrates and lignin increase 

rapidly in stem and leaves (Van Soest 1982) , and there is a concurrent decrease 

in protein nitrogen and digestibility (W aghorn and Barry 1987). There is an 

associated reduction in digestibility and intake with these changes (Minson 1982). 

However, Holmes (1987) stated that pasture digestibility does not affect DM 

intake consistently when pasture allowance is restricted but it does affect 

metabolizable energy intake. A high percentage of fibre (ADF, NDF) in the diet 

decreases voluntary feed intake and digestibility (Linn and Martin 1991 ). This 

means that the intake of pasture will usually decrease during summer and autumn; 

this factor contributes to the steeper decline in the New Zealand milk yield curve 

compared with that of US drylot feed cows (Edwards and Parker 1994). 

Environmental factors affecting the nutritive value of forages are: 

temperature, solar radiation, water stress and nutrient deficiencies (Linn and 

Martin 1991 ;  Buxton and Fales 1994). These environmental factors impact on 

plant maturity and hence forage quality and determine the degree of variation in 

forage quality throughout the year (Buxton and Fales 1994). 

The changes in pasture DM digestibility demonstrate a seasonal trend. 

Thus, pastures in New Zealand have a high digestibility in winter and spring; and 

this falls in summer and increases again in autumn (Bryant and Trigg 1982). 

In summary, while many factors affect the nutritional characteristics of 

pastures, the two main sources of variation are environmental and plant factors. 

Environmental factors are difficult to control, but plant factors can be mitigated 

through grazing management 



New Zealand feeds 42 

3.1.2 New Zealand pastures 

Information on the nutritional characteristics of pastures in New Zealand 

is limited (Table 3 . 1 ). Most of the pasture data shown in Table 3.1  were derived 

by proximate analysis in which the organic components are expressed as a 

proportion of the dry matter (DM) to allow comparisons between feeds. Crude 

protein is calculated by multiplying the total nitrogen concentration of the plant 

by 6.25 (Kjeldahl method). A common feature among the species reported in 

Table 3.1 is that there is a lack of detail on nutritive parameters of pastures which 

are important in dairy cattle nutrition. Dry matter, CP and energy are of vital 

importance in animal nutrition but they do not adequately describe the potential 

of various pastures for achieving high levels of animal production. Also, it is 

important to highlight the variability in DM, CP, DMD and ME presented in 

similar species throughout the year, especially between seasons. Data on seasonal 

variation in pasture nutritive value is shown in Table 3 . 1 .  For example, the effect 

of pasture maturity can be seen on the concentration of CP, as maturity increases, 

CP decreases. The CP concentration of pastures usually varies from levels of 5% 

of the DM for browntop (Agrostis tenuis) summer pasture to 28% approximately 

for white clover (Trifolium repens). The DM percentage for ryegrass-clover 

. swards varies dramatically between seasons from 15% in spring to 30% in 

summer. A similar variation can be seen in other nutritional parameters such as 

digestibility, ME content and minerals. The highest :ME content (12.2 MJ/kgDM) 

is reported for white clover. Other forages with :ME content over 12 MJ/kgDM 

are ryegrass-clover mixtures of spring immature pastures and Tama ryegrass .  



New Zealand feeds 43 

Table 3.1. Nutritional parameters of New Zealand pastures. (Sources: Bryant 

et al1• (1983); Holmes and Wilson2 (1987) ; Ulyatt et al3• (1991); Ulyate et al. 

(1980); Lancashire and Ulyate (1974) ; Rattray and Joyce' (1974) ; Ulyatt7 

(1981); John and Lancashire8 (1981)). 

Pasture Type Sou• DM' DMDc cpt MEMJe cat Pg M� Nai 

% % ------------gr per kg DM--------------

R:yegrass/clover 
Ry 70%-Cl30% 1 15 74 1 88 7.6 3.2 2.2 2.2 
Pressed pasture 1 19 71 161 6.8 2.8 1 .8 1 .6 
Spring leafy 2 14 75 240 1 1 .8 6.0 4.5 1 .5 1 .5 
Spring good quality 3 78 253 1 1 .2 4.5 3 2 1 .2 
Spring short 4 15 220 12.0 
Spring mixed 4 15 200 1 1 .2 
Spring rank 4 18  150 10.3 
Summer Jeafy 2 20 150 10.0 8.5 4.0 2.0 2.0 
Summer Jeafy 4 18  150 10.3 
Summer dry ,stalky 4 30 65 100 8.0 
Summer good quality 3 67 148 10.3 4.5 3 2 1 .2 
Autumn 4 15 250 10.8 
Autumn good quality 3 72 255 10.8 4.5 3 2 1 .2 
Winter,autumn saved 2 17 200 10.0 7.0 4.0 1 .8 1 .5 
Winter leafy 2 14 260 1 1 .2 7.0 4.5 1 .5 1 .5 
Winter short 4 15 250 1 1 .2 
Winter good quality 3 79 253 1 1 .2 4.5 3 2 1 .2 
Kikuyu grass,summer 2 22 140 8.5 6.0 3.9 1 .8 0.6 
Brownto� dominant 

AutumnJeafy 4 15 200 10.8 
Winter 4 15 220 1 1 .0 
Spring 4,5 15 82 220 1 1 .5 
Early summer 4 20 170 9.0 
Mid summer 4 50 50 7.0 
Spring 5 82 221 



New Zealand feeds 44 

Pasture Type Soua DMb DMDc Cpd MEMJe Cat Pg M� Nai 

% % ------------gr per kg DM--------------

Perennial Ryegrass 6 205 1 1 .7 
Primary growth ryeg 7 83 21 1 
Trimmed ryegrass 7 80 148 
Regrowth ryegrass 7 81  139 
Paspalumjeafy 2 18  180 10.5 7.5 4.0 2.5 0.6 
Paspalum flowering 2 23 100 9.3 5.6 3.0 2.5 0.4 
Red clover ,spring 2 17 280 1 1 .5 1 1  3.5 3 .0 0.8 
Red clover pre-bloom 4 18  230 1 1 .0 
Redclover full-bloom 4 25 180 10.0 
Tama,ryegrass 2 12 240 12.0 4.0 4.0 1 .5 2.5 
Tama ryegrass leafy 4 15 240 12.0 
Paroa ryegrass 4 15  230 1 1 .0 
Maku lotus 8 267 
Lotus com"empire' 8 71  218 
Lotus corn "maitland" 8 70 205 
Fakir saifoin 8 78 213 
White clover 6 258 12.0 
White clover mature 7 74 236 
Whiteclover regrowth 7 80 271 
White clover 2 15  280 12.2 12  4.0 3.0 3 .0 

a = s--, b = Dry matter, c:: Dry matter digestibility, d = Crude prot.eiB, e = Metabolic euer"gY iD Mep joules, r = Caldam, 
1: = l'llo8pbona, 11 = Mapeslam, I = Sodium. 

3.2 Sllage 

Silage is produced through the controlled fermentation of forages. High 

quality-high intake silage is the product of high digestibility at harvesting and 

appropriate fermentation in the silo (Gordon 1989). Thomas and Thomas (1989) 

recognised maturity of the crop at cutting as the most important factor 

detennining the nutritive value of silage because it will determine silage 



New Zealand feeds 45 

digestibility which is almost always lower than that of fresh pasture because of 

the loss of water soluble carbohydrates during fermentation (Holmes and Wilson 

1987). Other factors affecting silage quality are: chop length, wilting, additives 

and anaerobic storage (Gordon 1989). Silage is a preferred form of conservation 

over hay because it requires a shorter period of herbage accumulation, provides 

resistance to unfavourable climatic conditions and often has higher digestibility 

(Hodgson 1 990). Silage quality is very variable, it ranges from a product unable 

to support maintenance requirements to a high quality forage providing the major 

part of a ration supporting high levels of production (Rogers 1 985). However, 

animal intake and nutritive value per unit of DM is usually low ranging from 10.5 

MJME/kgDM for maize silage to less than 8 MJME/k:gDM for poor quality 

pasture silage (Frame 1991). In New Zealand silage is made during periods of 

pasture swplus to be fed during periods of pasture shortage. This system of silage 

making has contributed to farmers producing large quantities of silage of medium 

to poor quality (Table 3 .2), because pastures are usually mature and stemmy at 

the time of harvest. Table 3 .2 shows that pasture silage DM content varies from 

28 to 20%, digestibilities range from 70% for kiwifruit silage to 55% for poor 

quality pasture silage. Additive use (e.g. formaldehyde and formic acid) may 

increase digestibility values by 1-2 points compared with high quality pasture 

silage. Kiwifruit silage shows a great potential as a supplementary feed for 

grazing dairy cows because it has a low crude protein content and high ME (1 1 .5 

MJ/kg DM). 



New Zealand feeds 46 

Table 3.2. Nutritional parameters of New Zealand silages. (Sources: Holmes 

and Wilson1 (1987); Barrf (1975); Ulyatt et al3• (1980); Farm Facts4 (1993); 

Bramwell et al5• (1993); Parker W.J' (1994) pers.comm; Densley R . .T'. (1994) 

pers.comm). 

Silage type Soua DMb D:MDc Cpd :MEMJe Cat pg Mt Nai 

% % --------Grams per kg DM.------

Grass/clover mix 
Good quality 1 23 60 200 10.0 7.0 4.3 1 .7 1 .7 

Poor quality 1 28 50 150 8.0 5.5 2.8 1 .4 1 .6 

Pasture silage 2 20 64 151  9 .7 

P+formaldehyde 2 22 63 148 10.2 

P+formaldehyde+formic 2 20 62 140 9.2 

Lucerne 1 20 200 9.5 10.0 2.6 2.0 0.5 

Lucerne high moisture 3 23 160 10.5 

Maize,early dent 1 30 65 80 10.3 3 .0 2.0 1 .2 0.1 

Maize ,mature 3 35 80 10.5 

Maize silage 7 34 67 68 10.4 

Maize silage 7 36 68 1 1 .5 

Maize silage 7 34 66 71  10.3 

Maize silage 7 31  70 71  10.9 

Maize silage 7 32 64 66 1 0.0 

Maize silage 7 34 66 71  10.3 

Kiwifruit wholefruit 4 14 90 1 1 .5 

Kiwifruit skin&seeds 4 38 1 10 8.0 

Kiwifruit silage 5 16 170 

Kiwifruit silage 6 86 70 102 

Kiwifruit/grass 6 91 58 151  

a • 8oUrce , b • Dry -tt.r, c •  Dry -tt.r 4igeatib111ty, 4 • crua. prot.in, • • Metabolic -rgy in 
Mega joul.-, � • C&lci-. g • Phoaphoru., h • lllaQDeai-. 1 • 8o41-. 



New Zealand feeds 47 

3.3 Hays 

Hay is produced by conserving forages through drying. Hay quality is 

highly dependant on the quality of the standing forage at the time of harvesting. 

Other important factors in determining hay quality are nutrient losses during 

drying and harvesting (respiration loss), and hay losses during storing (Rotz and 

Muck 1994). 

As with any other forage, hay quality depends on the amount consumed by 

animals and its digestibility. Rogers (1985) pointed out that in high rainfall areas 

hay cannot satisfactorily be cured until late spring-early summer when crops are 

generally mature: digestibilities range from 50-63% with ME concentrations of 

6.7-9.0 MJME/kgDM. In this sense, the nutritional effectiveness of hay is limited 

by its digestibility. Hay quality is therefore of vital importance if high levels of 

animal performance are to be achieved. 

Hay digestibility is generally 5% to 15% lower than that of the forage from 

which is made (Holmes and Wilson 1 987). In New Zealand bays are generally 

harvested in December and January when pastures are maturing and developing 

seed heads. Hay quality is therefore generally medium to poor, and could be 

improved through earlier harvesting (November). This would result in lower 

yields at harvest and higher costs per kgDM, but this ignores the nutritive value 

of the hay and on an energy protein, or animal production potential basis,  for 

example, costs could be lower overall for harvesting strategies that produce high 

quality bays. 



New Zealand feeds 48 

The summary for New Zealand bays (Table 3.3) shows that they have a 

DM content of 85%, digestibility of 54-62%, ME concentrations of 7.0-9.7 

MJMFJkgDM and CP of 170-80 glkgDM. Generally, lucerne bays are of greater 

quality, with digestibility ranging from 66-55%, ME concentration from 10.5-8 

MJME/kgDM and CP content ranging from 200-120 g/kgDM. 

Table 3.3 Nutritional parameters of New Zealand bays. (Sources: Holmes and 

Wllson1 (1987); Barrf (1975); Ulyatt et al3• (1980)). 

Hay type Sou• DMb DMDC cpd MEMJe car pg MtNai 

% % --------Grams J)er leg DJvi---------

Grass-clover mix 
Good quality 1 85 60 170 9.7 8.0 4.0 2.0 2.0 

Medium quality 1 85 57 1 10 8.5 6.0 3 .5 1 .9 1 .7 

Poor quality 1 85 50 70 7.3 4.0 3 .0 1 .8 1 .5 

Hay early 1Nov 2 62 122 9.0 

Hay late IDee 2 54 100 7.8 

Lucerne pre-bloom 1 ,3 85 67 200 10.5 

Lucerne early-bloom 1 ,3 85 65 1 80 9.8 

Lucerne mid-bloom 1 ,3 85 60 170 9.0 

Lucerne full-bloom 1 ,3 85 55 150 8.5 

Lucerne weathered 1 ,3 85 55 120 8.0 

Red clover 3 85 150 8.5 

Oat milky ripe 3 85 60 8.0 

Meadow Ha� 

Young leafy 3 85 120 9.0 

Mature 3 85 100 8.0 

Weathered 3 85 80 7.0 

a • 8ollrce, b • Dry -tter, c• Dry -tter 4igeat111111ty, 4 • cru4e proteiD, • • .. tabolic -rgy 1D 
llega jouJ.e., f • C&lciua, g • Phoaphoru. , h • KagDeaiua, 1 • �-. 



New Zealand feeds 49 

3.4 Straws 

Straws are the dried stems and leaves of forages after the removal of seeds. 

They may be conserved foll owing threshing of grass for seed or cereal crops. In 

general, straws are characterised by low nitrogen content, low digestibili ty, low 

mineral content an d  a low rate of ru men outflow (Preston and Leng 1987 and 

Table 3 .3). These characteristics do not al low a high DM intake (B rookes et al. 

1992) and hence decrease the potential feeding value of straws. 

Straw quality can be improved by physical, chemical and microbiological 

methods. However, straws are often considered to be of such low feeding val ue 

that they are burned or cul tivated back into the soil in countries with speciali sed 

livestock production systems. In New Zeal an d  straws are rarely fed to cattle 

because of their low feeding value (Table 3 .4). On average they have a DM 

content of 85%, digestibility ran ges from 40 to 50%, and  CP and ME varies from 

40 to 60 and 6.5 to 8 glkgDM, respectively. 



New Zealand feeds 50 

Table 3.4. Nutritional parameters of New Zealand straws. (Sources : Holmes 

and Wilson1 (1987); Ulyatt et al2• (1980). 

Straw type Sou• DMb DMDC cp<� MEMJe Cat pg Mgh Nai 

% % ------------CirCUllS �r kg DM---------

Barley 1 85 40-50 40 6.5 3.0 0.8 1 .7 1 . 1  

Barley 2 85 40 7.0 

Wheat 1 85 40 7.0 

Maize stover 1 85 40-50 50 7.5 6.0 1 .0 4.5 0.7 

Corn stover 2 85 50 7.0 

Pea 1 85 40-50 80 7.0 16.0 1 .2 

Rye grass 2 85 60 8.0 

Rye grass 1 85 40-50 60 7.5 4.0 3.0 1 .5 1 .5 

Oats 2 85 40 7.0 

a • sourc e ,  � • Dry -tter, c• Dry -tter 41geat�11ity, 4 • crude protein, • • Met&bo1ie eDergy in 

Mega jou1ea, f • C&1eiua, g • Phoaphorua, h • llagzaeaiua, 1 • Boc!iua. 

3.5 By-products 

Products obtained after the processing of plant and animal materials for 

food are called by-products. The feeding value of industry by-products can vary 

considerably. This variation is strongly influenced by the original product and by 

the method of processing (De Visser and Steg 1988). 

In New Zealand, Bramwell et al. (1993) analysed the feeding value of 

horticultural products such as apple pulp, apple pomace, carrots, rejected kiwifruit 

and corn. The authors found that horticultural by-products have a high feeding 

. potential for ruminants (Table 3 .5). New Zealand has a large and expanding 

horticultural industry which produces a range of by-products (Table 3 .5) that are 

suitable for livestock feeding. 



New Zealand feeds 51  

A short term experiment (Holmes et al .  1 994) at Massey University showed 

that lactation could be prolonged and milk production increased when pasture was 

supplemented with a 50:50 mixture of grass silage and apple pomace. The milk 

production benefits exceeded estimated milksolids value associated with a loss in 

pasture cover and the failure of cows to gain condition which occurred because 

lactation was extended by 32 days. 

The information presented in Table 3.5 highlights the high energy value 

(over 1 1  MJME) and digestibility (over 70%) of some horticultural by-products, 

especially derivatives of apples, pears, peaches and kiwifruit. Crude protein 

contents, however, tend to be low (less than 10%). These products have potential 

to complement high quality fresh pasture which have high levels of crude protein. 

Thus appropriate by-products could help to provide grazing animals with a 

balanced diet. Also, because they are a "waste" material they are usually 

inexpensive compared to more traditional supplements such as · hay and silage. 

Brewer's grain may be a suitable product to supplement grazing dairy cows, it has 

a high CP (25%), but around 40% of that protein is "by-pass" protein that can 

help to balance the amino-acid profile of the cow (Lean 1987). Brewer's grain 

also contains an acceptable level of :ME (10 MJ/kgDM). 



New Zealand feeds 52 

Table 3.5. Nutritional parameters of New Zealand by-products. (Sources: 

Bramwell et al1• (1993); Ulyatt et al2• (1980) ; Parker and Edwards3 (1993) 

pers.comm. ; Wilkins4 (1993); Farm Fac� (1993); Holmes and Wilson6 (1987)). 

Name Soua DMb DMDc CPd MEMJe Caf pg M� Nai 

% % ----------CJraJilS �r leg DM----------

Apple bucher 4 40 86. 1 10  13 . 1  0.9 0.9 

Apple pomace 1 ,4 70 74.4 61  13 .7 0.9 0.9 

Apple" silo "pomace 3 23 

Apple Fresh pomace 3 21 

Apple pressings 1 ,4 89 89 47 13  0.9 0.9 

Apple pulp 1 ,4 25 74 60 8.4 0.9 0.9 

Apple pulp dried 1 89 33 9.5 

Apples 2 1 8  30 1 1 . 1  

Brewer's grain 2 35 250 10.0 

Brewer's grain 6 24 230 10.0 3 6. 1 1 2 

Citrus pulp 2,4 1 8  92 70 12.1 18 .6 1 . 1  1 .50 0.9 

Citrus pulp 1 89 78 10.7 

CJrape Pomace 2 38 140 5.2 

CJrape pressings 1 80 142 

CJra� pulp 1 ,4 91  91  33 4.8 0.4 0.5 0.8 

Kiwifruit 5 1 5  50 1 1 .5 

Kiwifruit pulp 4 16 44.5 1 00  8.6 

Kiwifruit silage 4 21 16.2 106 1 1 .0 

I Kiwifruit slices 4 16  90.8 1 00  12.9 

Maize huslcs 2 90 40 9.0 

Molasses 6 75 40 12.0 12 1 4 .3 1 .5 

Peaches 4 80 50 12.0 

Pears 4 88 56 13.2 

Peas 2 18  140 10.9 

Potato offal dried 1 94 1 17 

Sugar beet pulp 2 1 1  120 10.2 

Tomatoes 4 13 235 1 1 .4 3.9 5.5 1 .8 

Winecy pomace 1 ,4 94 93.5 1 12 7.3 
a • soarce ,  b • Dry -tter, c• Dry -tter 41geat.1bility, 4 • c:rws. proteiD, • • •tabolic -rgy iD 
*CJa joul.ea, f • C&lci-. g • Pboapborua, h • llagDeaiua, 1 • 8odiua. 



New Zealand feeds 53 

3.6 Concentrates 

Concentrates are feedstuffs that contain a considerable quantity of energy 

and/or protein as a percentage of total nutrients. These are not widely used for 

livestock feeding in New Zealand because their cost is high relative to other feeds. 

High energy feedstuffs generally have a low concentration of protein. The energy 

in high energy concentrates comes from water soluble carbohydrates and fats 

(Church and Pond 1 988). High energy concentrates are mainly represented by 

cereal grains and milling by-products. They are high in both DM content and 

digestibility (Holmes and Wilson 1987). 

High protein concentrates (meals) are often derived from animal and plant 

sources processed as either animal feeds (fish meal) or industry by-products 

(blood meal, oilseed meal). Generally, protein of animal origin contains an 

important amount of rumen undegradable protein especially if it has been treated 

when dried. Nevertheless, the process for producing fish and meat meals can 

strongly influence their nutritive value and uniformity of quality. 

Concentrate quality generally varies less than that of pasture. However, 

cereal concentrate composition also depends on plant variety, climate and fertiliser 

factors. The nutritional characteristics of New Zealand concentrates are presented 

in Table 3.6. 

·A wide range in the nutritional value of the same feeds is evident for some 

feeds. For example, barley is reported by three different authors to have widely 

different values for energy, crude protein and minerals. The same situation occurs 

for maize, oats, wheat and bran. These values highlight the variability in the 



New Zealand feeds 54 

nutritional characteristics of feeds that may be associated with environmental and 

management factors (see earlier discussion). It is important that this variability is 

accounted for in feeding programmes if sustained high animal performance is to 

be achieved. 

Table 3.6. Nutritional parameters of New Zealand concentrates. (Sources: 

(Uiyatt et al1• (1980); Holmes and Wilson2 (1987); Wilson3 (1978); Harris and 

Douglas4 (1981); James5 et al. (1987)). 

Name Sou a DMb DMDC cp<� MEMJe Cat pg Mt Nai 

% % --------Grams per kg D M----------

Barley 1 85 120 12.5 

Barley 4 86 97 10.7 0.5 3 .8  1 .5 0.2 

Barley 2 86 85 1 10 1 3 .0 0.6 4.4 1 .8 0.3 

Bran 1 85 170 9.6 

Bran (Wheat) 2 86 1 60 9.8 1 .0 . 1 2.0 6.0 0.4 

Buttermilk powder 1 93 340 1 3 .2 

Dried blood 1 90 900 10.0 

Fish meal 1 92 750 1 1 .5 

Grass meal 3 85 1 80 1 0.0 

Linseed cake 2 87 300 12.0 4.4 8.0 6.0 0.7 

Linseed cake 1 85 350 1 2.0 

Lucerne meal 1 85