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Item The effects on pasture of the winter grazing of dry dairy cows : a thesis presented in partial fulfilment of the requirements for the degree for the degree of Master of Agricultural Science at Massey University(Massey University, 1971) Matthews, P N PWith the demand for higher production, but probably more from economic necessity, stocking rates on New Zealand dairy farms have increased markedly over the past ten years. The average herd size has over this period increased from 57 cows in 1960 to an estimated 98 cows in 1970 (N.Z. Dairy Board, 1970); this figure however takes no account of any increase in farm size over this period. Increased stocking rates on a fixed area of land has not been associated with similar increases in pasture production,indeed, the reverse may be the case (Campbell, 1966; Holmes, 1962; Morley 1966). The increased production has been a function of increased utilization of the pasture grown (Campbell, 1966). With such trends management decisions with regard to pasture and animal become critical, mistakes having long reaching repercussions, A critical period on all seasonal dairy farms is over the winter when management decisions can affect butterfat production for the entire lactation (Wallace 1958), Increased stocking rates have heightened this wintering period as a result of mainly two factors : (i) An increased milking herd means lower pasture surpluses in the spring, hence lower levels of conserved fodder for periods of low pasture production. (ii) It is at this time of the year that damage to pastures through grazing appears most severe.Item Duration-controlled grazing of dairy cows : impacts on pasture production and losses of nutrients and faecal microbes to water : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2013) Christensen, Christine LynneMitigation strategies for improved environmental sustainability of the New Zealand dairy industry need to focus on reducing the transport of nitrogen (N) from urine patches and phosphorus (P) and faecal microbes from dung patches to waterways. One strategy is Duration-controlled grazing (DC grazing), a system based upon shorter grazing periods on pasture (4 hours) and removing cows to a stand-off facility for rumination and excretion. The stored effluent is applied to pasture as a slurry at an appropriate time when nutrients are required and soil conditions are suitable. A three year field study was established in the Manawatu to compare key features of DC grazing with a standard grazed (SG) system. This thesis explores the impact of a DC grazing system on the losses of N, P, potassium (K) and faecal microbes to water through drainage and surface runoff. It also investigates the effects of such a system on pasture production and intakes of pasture by cows. Pasture accumulation was the same for both treatments in the first year, but there was a 20% and 9% decline on the DC treatment in the subsequent two years. This was due to the way that slurry applications were managed. A large amount of slurry (212 kg N/ha) was applied in the first year, and no slurry was applied in the second year. In the third year slurry was applied four times at a total rate of 115 kg N/ha. The study indicates more frequent application of all nutrients captured in the effluent from standing cows off is required to maintain pasture production. Compared to the SG plots, the reductions in N losses from DC grazed plots were large, with an average 52% reduction in NO3- and 42% reduction in total N leached. Reducing urine deposition during autumn grazings appeared to have the largest impact on reducing NO3- leaching. Runoff losses of N were small and similar between treatments. The losses of P were small through both surface runoff and drainage. There was a large variation in runoff volume, which resulted in highly variable P runoff loads across plots and between treatments. The average 32% reduction in total P load from DC grazed plots was not significantly different from SG plots. Useful predictors of P load lost from all plots were runoff depth and the time cows spent grazing. Faecal microbe losses were also similar between treatments, with the useful predictors of faecal microbe concentration across all plots being the number of days since grazing and the climate after grazing. The amount of K applied in slurry and urine had a large influence on both soil and herbage K. It was determined that in a DC grazing situation, the K-rich liquid component must be included in the applied slurry to maintain soil K levels. The OVERSEER® nutrient budgeting software was able to simulate nutrient cycling in the DC grazing system reasonably well. The total N loss from the system was predicted accurately, although the relative proportion of N in drainage and runoff was not. Several opportunities for further work arise from this research. While DC grazing is a tool that could be implemented to significantly reduce N leaching losses, the management of collected excreta needs to be further developed to ensure pasture production gains are realised, or at least maintained. The combined effects of reducing treading damage and DC grazing should be investigated. Finally, a comprehensive economic analysis of standing cows off should be undertaken.Item A study of the effects of defoliation and water stress on growth and development of Stylosanthes hamata (L.) Taub. cv Verano : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agronomy at Massey University(Massey University, 1986) Sayan, TudsriVerano stylo (Stylosanthes hamata (L.) Taub.) is an important pioneer legume in the tropics and its potential as a pasture legume under grazing appears to be promising in Thailand. This thesis was carried out in two parts - the first part was conducted in the Controlled Climate Rooms at the Plant Physiology Division, DSIR, Palmerston North, New Zealand. The aim of these studies was to obtain basic information on growth patterns and the response of Verano stylo to cutting at different intensities, frequencies and stages of growth and at two levels of water stress in terms of quantity and quality of herbage produced. The second part was a grazing trial conducted at Muaklek, Thailand, to test the grazing management hypothesis derived from the Controlled Climate Room studies. The results from the Controlled Climate Room studies showed that the growth and development of intact Verano stylo was slow at the pre-flowering stage and increased rapidly after the onset of flowering. Maximum growth rate of 2.04 grams/plant/day was recorded between 70 and 80 days and maximum dry weight of 105 grams/plant was achieved approximately 108 days after seedling emergence. During this post-flowering stage, plant growth in terms of plant dry weight, branch development, leaf number and leaf area increased rapidly. Flowering commenced 35 days after seedling emergence and continued throughout the experimental period. Stem was the major plant component, followed by the inflorescence and leaf fractions. In terms of the response to various cutting regimes, the results showed that the more severe the cutting the more deleterious was the effect on regrowth. Cutting the primary branches had a greater effect on plant regrowth in terms of plant dry weight, branch number, leaf number and leaf area than defoliating the main stem. Severe cutting of primary branches (i.e. to node 0) plus hard cutting of the main stem (i.e. to node 3) resulted in the death of the plant after two cuts. When defoliation was delayed to the later stage of growth (near maximum growth rate), severe cutting of the primary branches (i.e. to node 0) caused extensive plant death following only a single cut. All growth parameters recorded were markedly reduced when the interval between cutting was decreased. It is suggested that the response of Verano stylo to defoliation is dependent upon the number and especially the size of the primary branches, the number of growing points, the amount of stubble reserves and the residual leaf area immediately after cutting. The differences in yields were largely due to changes in the stem and to a lesser extent the inflorescence and leaf fractions. Growth of the plant in terms of plant dry weight, branch number, leaf number and leaf area were reduced to a greater extent under severe than under mild water stress. The differences in plant dry weight between the two levels of stress were largely due to the size of the stem fraction. After rewatering there was a rapid increase in growth by both the previously mild and severe water stressed plants, resulting in a marked increase of all the variables recorded. However, growth of plants previously under severe water stress was less than those previously under mild water stress. The increase in total plant dry weight was due to an increase in all plant components, especially leaf and inflorescence fractions. Severity of cutting had less effect on plant variables than water stress. The effect of cutting was more apparent under mild water stress than under severe water stress in terms of plant dry weight, branch number and leaf area, and continued to show this effect on rewatering with respect to leaf number and leaf area. Verano stylo herbage quality, as measured by crude protein concentration, was relatively high even in the uncut control plants. Defoliation increased the protein concentration, but within the cutting treatments there was little effect of cutting intensities and frequencies on the crude protein concentrations of all plant components, except the stem fraction which was slightly superior under frequent than infrequent cutting. The protein concentration was higher in the leaf and inflorescence and lower in the stem at all cutting intensities and frequencies. Severe moisture stress increased the crude protein content in the leaves, stems and inflorescences compared with mild moisture stress and continued to show this effect on rewatering with respect to the leaf and stubble fractions. Hard cutting in the drought period also increased protein concentrations in the leaves, stems and inflorescences compared with lax cutting and continued to show this effect on rewatering with respect to the stubble and stem fractions. Although the crude protein concentrations in different plant parts and for different cutting intensities, frequencies and stages of cutting and for different water regimes were relatively small, the amounts per plant were large due to the substantial and significant differences obtained in dry weight between treatments. The increase in crude protein was largely due to the inflorescence fraction, especially under lax cutting. Crude protein yields were also seriously reduced under frequent and hard cutting of the primary branches. Previously stressed plants at either mild or severe levels greatly increased their crude protein yield after rewatering, and this was largely due to the crude protein yield of the leaf and inflorescence components. In terms of carbohydrate reserves, the results of this study clearly showed that the concentration of these reserves in the residual top and roots of Verano stylo were low (< 3% of dry weight), were comprised mainly of sugar and were independent of the stage, intensity and frequency of cutting. However, carbohydrate concentrations were substantially increased by severe and especially mild water stress. Starch was the major component and accumulated in all plant parts especially the stubble, stem and tap root fractions. The effects of cutting during the drought period were only evident in the stubble, inflorescence and tap root fractions - the levels declining with increasing intensity of defoliation, particularly of the starch fraction. However, these carbohydrates, especially the starch fraction in the stubble, stem and tap root, almost totally disappeared during the rapid recovery phase, suggesting it was used for regrowth. In terms of the amounts of carbohydrates, the results showed that the differences between cutting intensity were largely due to the differences in the residual dry weights especially in the stubble. Generally the more severe the cutting, the lower the amount of carbohydrates in the stubble. However, cutting frequency had no significant effect on carbohydrate accumulation. Severe water stressed plants accumulated only half the reserves of the mild water stressed plants during the drought period. Under both mild and severe water stress, the stem was the major accumulator of these reserves, particularly of the starch fraction. On rewatering, there was a marked increase in the accumulation of sugar akin to the increase in dry matter yields. However, starch yields in the stem and tap root showed a substantial drop during this period. During the drought period, hard cutting significantly depressed the accumulation of sugar and starch especially under mild water stress. In the roots only the starch fraction was affected. On rewatering, previous hard cutting continued to depress carbohydrate yield but only of the starch fraction of those plants under previous severe water stress. The results from the field experiment confirmed the importance of residual leaf and branch numbers on plant regrowth in terms of dry matter production, branch development, leaf number and leaf area and their persistence. Under climate room conditions, 6 weekly cutting produced significantly higher yields of all growth components than did 3 weekly cutting. However, under field grazing conditions frequent grazing (every 4 weeks) produced significantly higher yields than infrequent grazing (every 8 weeks). Frequent grazing also maintained a higher density of Verano stylo plants and a lower weed content. The results are discussed in relation to the possible grazing management of Verano stylo in Thailand.Item Studies of late spring grazing management in perennial ryegrass dominant pasture : a thesis presented in partial fulfilment of the requirements for the degree of PhD in Agronomy at Massey University(Massey University, 1981) Korte, Christopher JohnTwo grazing experiments and a mowing experiment were conducted to obtain information on the patterns of herbage accumulation and the tiller dynamics of "Grasslands Nui" perennial ryegrass (Lolium perenne) dominant pasture under a range of defoliation regimes during late spring/early summer. Defoliation intensity and defoliation interval were defined in terms of plant physiological criteria, that is, light interception and stage of reproductive growth. The effect of four late spring/early summer grazing intensity treatments, based on residual leaf area index (LAI), and two grazing interval treatments, based on light interception, were compared in the first grazing experiment. Net herbage accumulation was greatest when grazing was hard (LAI = 0.1-0.6) and least when grazing was lax (LAI = 1.5-2.5) in late spring (16.5 and 13.6 t DM/ha respectively). Grazing at 95% light interception reduced green herbage accumulation compared with grazing two weeks after 95% light interception (14.0 an 15.8 t DM/ha respectively). With lax grazing stemmy rank herbage developed, whereas with hard grazing dense leafy pasture with a higher ryegrass tiller density developed. The grazing interval treatments did not significantly affect ryegrass tiller density. The second grazing experiment compared the effects of the timing and intensity of spring grazings on herbage accumulation and ryegrass tiller dynamics. Interrupting reproductive growth of ryegrass at the head emergence stage, compared with at the start of culm elongation, did not increase herbage accumulation significantly although it resulted in a higher proportion of stem and a lower proportion of lamina accumulating. As in the first experiment, hard grazing in late spring increased herbage accumulation compared with lax grazing. Hard grazing appeared to increase herbage accumulation by reducing herbage death and decay, not by increasing herbage growth. Ryegrass tiller density was greater in hard grazed swards than lax grazed swards in summer. This difference was mainly due to a higher tiller appearance rate in hard grazed swards. The difference was still apparent in winter although all treatments were grazed similarly during late summer and autumn. Herbage accumulation was greater in autumn where grazing had been hard the previous spring/summer, partly due to the higher tiller density. Interrupting reproductive growth at the head emergence stage markedly reduced the density of vegetative tillers compared to interrupting reproductive growth at the start of culm elongation. Due to rapid tillering after interruption of reproductive growth this difference quickly disappeared. The effects of the time of cutting to control reproductive development and the subsequent cutting interval on herbage accumulation and tiller dynamics of ryegrass pasture were examined in the mowing experiment. Herbage accumulation was reduced by more frequent mowing and where reproductive growth was prevented. Tillers present at the start of each rest period contributed most herbage because new tillers were relatively small. After the first mowing, new tillers were generally of similar weight to older tillers at the end of rest periods. It appeared that during summer, under conditions of adequate moisture and nutrients, the tiller dynamics of perennial ryegrass swards were little influenced by mowing frequency. It was concluded that the objective for late spring grazing management should be to encourage leafy vegetative pastures and to prevent rank stemmy pasture developing. Dead culms in rank pasture reduced the digestibility of herbage and shaded photosynthetic tissue. Leafy swards had higher accumulation rates and a higher tiller density than stemmy swards. Methods of achieving leafy pasture on farms by combinations of hard grazing, forage conservation and mechanical topping are discussed.Item Sulla (Hedysarum coronarium L.) : an agronomic evaluation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University(Massey University, 1993) Krishna, Hari; Krishna, HariThis thesis reports three studies conducted on the agronomic evaluation of the recently introduced forage legume species sulla (Hedysarum coronarium L.) cv. Necton, for its potential use in animal production systems in New Zealand. The utilisation of forages, grasses and legumes, in New Zealand is predominantly by grazing in situ. Sulla was introduced to New Zealand for soil conservation, but its use as a forage under a cutting regime is well known in the Mediterranean countries. Information was inadequate for its use under a grazing regime. A preliminary study was conducted under sheep grazing to assess annual herbage production, seasonal patterns of DM production and persistence. Nodulation failure resulted in the application of 100 kg N ha-1 after each grazing. Severe grazing (H=70-75% herbage consumed) and less severe (L=60-65% herbage consumed) grazing intensities were imposed at the early reproductive (ER) and late reproductive (LR) growth stages. The resultant management treatments over one year were ERHHHH, ERHLLL ERLHHH, ERLLLL, LRHHH and LRLLL. Grazing intensities did not affect herbage production as residual herbage senesced after grazing. The annual herbage production ranged from 12000-20000 kg DM ha-1 in the ERGS and LRGS treatments. Plant density declined 83 and 46% in the ERGS and LRGS respectively. Regrowth originated from the crown region in both growth stages. Autumn grazing management, ineffectively nodulated plants, inadequate weed control and poor stand persistence were identified as constraints to herbage production and needed further research. An effective Rhizobium strain ICMP 10149 was reisolated, and a concurrent trial elsewhere, not by the author of the thesis, identified Stomp 330 E a preemergent herbicide as suitable for Sulla. A greenhouse defoliation trial was conducted to elucidate the influence of plant growth stage at defoliation and grazing intensity on herbage accumulation in the absence of compounding factors such as selective grazing and trampling. Plants were defoliated to 1, 7, 15 and 30 cm at the late vegetative (LV), midstem elongation (MSE) and early flowering (EF) growth stages. Across growth stages, the residual leaf area was 0, 84, 180 and 415 cm2 respectively. Destructive harvests were carried out on days 0, 14, 25, 40 and 60 after defoliation. Plant maturity at defoliation and defoliation intensity were determinants of herbage increase in 60 days of regrowth. Complete (1 cm) defoliation at the LV growth stage resulted in a smaller root system, decreased starch accumulation and reduced plant size. Defoliating to 15 cm at the EF growth stage produced the maximum regrowth of herbage, maintained high taproot starch and root mass. A grazing trial was designed to evaluate annual herbage production, seasonal patterns of DM production and plant persistence in an effectively nodulated stand with minimum weed competition. Severe (H=70-80% herbage consumed) and less severe (L=60-70% herbage consumed) grazing intensities were applied at the late vegetative (LV), midstem elongation (MSE) and early flowering (EF) growth stages. LVHHHH, LVLLLL, MSEHHHH, MSELLLL, EFHHH and EFLLL were the resultant management treatments over one year. Grazing intensity did not influence herbage produced as the postgrazing herbage senesced. Across intensities, the annual herbage produced ranged from 22000-25000 kg DM ha-1 for the various growth stages. Herbage accumulation rates were 55 Kg DM ha-1 d-1 in early summer and peaked at 78 kg DM ha-1 d-1 in late summer and early autumn. Plant density declined 79, 74 and 29% over a year in the LV, MSE and EF treatments respectively and remaining plants subsequently disappeared. Late autumn grazing in wet soil conditions resulted in significant plant losses which affected spring herbage production. Sulla was best grazed or cut at the EF growth stage for maximum herbage production and persistence. Complete removal of herbage maximised utilisation as remaining stubble senesced and did not contribute to herbage accumulation. Under grazing sulla was short-lived and thus should be managed as an annual forage species. Allowing seed to shatter may be a potential management tool for the maintenance of stands. An autumn sowing for spring utilisation to exploit winter growth activity may be advantageous. However, late autumn grazing especially with high stocking densities under wet soil conditions should be avoided, and, in general, damage to the crown should be minimised. Although a residual leaf area (200 cm2) on the stubble would improve the rate of regrowth this would appear difficult to attain under grazing. It may be best to cut sulla to exploit its winter growth activity. Sulla has potential as a special purpose forage when summer and autumn/winter pasture deficits restrict animal production.Item A study of spring grazing management effect on summer-autumn pasture and milk production of perennial ryegrass x white clover dairy swards : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.) in Pasture Agronomy at Massey University(Massey University, 1994) Da Silva, Sila Carneiro; Da Silva, Sila CarneiroEvidence generated at Massey University demonstrated the importance of the manipulation of ryegrass reproductive growth during spring to pasture production. It showed that lax grazing of pastures during spring followed by hard grazing at the time of anthesis could result in an enhancement of summer-autumn herbage production, associated with an enhanced tillering activity of ryegrass plants. Such grazing management was called "late control", and it was thought to be an option for enhancing pasture production, particularly in dairy farms, where conditions for manipulating reproductive swards would be most favourable. Thus, the objectives of this study were (i) to evaluate the effects of this late control spring grazing management on summer-autumn herbage production and botanical composition of ryegrass-white clover dairy pastures, and (ii) to investigate the consequences of such a grazing management strategy on pasture quality, herbage intake and milk production by dairy cows. Three field experiments are reported. The first two were sward-based experiments whose results were used to plan and set up the third experiment, which involved evaluation of both sward and animal effects. The results from Experiment 1 (October 1990 to April 1991) and 2 (October 1991 to April 1992) confirmed the expectations of enhanced spring and summer-autumn herbage accumulation from a late control grazing management over the spring time. An average increase in production of the order of 750 Kg DM/ha (25%) was obtained from October to November, and of 1.0 t DM/ha (20%) was obtained from January to April in both years, with ryegrass accumulation being enhanced in Experiment 1 and white clover accumulation enhanced in Experiment 2. Evidence gathered about tillering activity was inconclusive, although it showed that tillers produced under the late control spring grazing management were bigger than those produced under the conventional hard grazing management. White clover response was variable from year to year. It was concluded that the timing as well as the intensity of execution of the late control were very important. Late control should be executed at the time of anthesis of the reproductive development of ryegrass plants (late November-early December), and the removal of seedheads and reproductive stems should be gradual, over two or three successive grazing cycles. Simulation of the implementation of this late control grazing management on a farm basis was then performed, based on the results from Experiments 1 and 2, in order to gain an overview about possible practical implications for farm practice. The models showed that the preparation of pastures to achieve the reproductive stage prior to late control was feasible and would not imply any decrease in the feeding level of dairy cows. However, more information was necessary on how to execute late control and whether or not the increased summer-autumn herbage accumulation could be converted to milk production. Further evaluation of late control grazing in Experiment 3 (October 1992 to April 1993) revealed that increase in spring herbage accumulation by 1000 Kg DM/ha (25%) was a consequence of the reproductive growth of perennial ryegrass plants, which caused a decrease in the digestibility of the herbage consumed from 78% to 75% due to the increased contents of senescent and grass stem material in the sward. On the other hand, increased summer-autumn herbage accumulation (1000 Kg DM/ha, 25%) after late control was due to enhanced accumulation of both ryegrass and white clover. The digestibility of the herbage was restored soon after late control. Despite the lower digestibility of reproductive swards during the control period, no significant reduction in the herbage intake of dairy cows was detected in comparison with animals grazing leafy and vegetative swards. However, the use of forage conservation to augment grazing pressure during the late control phase proved to be more effective than a grazing only strategy, since a large proportion of senescent material was allowed to form under those circumstances. The increase in summer-autumn herbage accumulation was associated with an increase in milk solids yield per cow of the order of 10%, with around 25 Kg milk-fat being obtained from the extra tonne of dry matter accumulated per hectare in late control pastures. It is concluded that the late control spring grazing management of perennial ryegrass-white clover pastures can be used as an option to enhance pasture production in dairy farms, particularly during the summer-autumn period, and that this increased herbage accumulation can be effectively converted to milk solids yield. The implementation of this grazing strategy into a farm context and its implications for farm practice are briefly discussed.Item An evaluation of a dairy systems study of the effects of contrasting spring grazing managements on pasture and animal performance : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph. D.), Pastures and Crops Group, Institute of Natural Resources, College of Sciences, Massey University, Palmerston North, New Zealand(Massey University, 1999) Bishop-Hurley, Gregory John; Bishop-Hurley, Gregory JohnTraditionally, the emphasis in dairying systems in New Zealand has been on maintaining pasture quality in late spring through increased grazing pressure and occasionally topping. Recent studies have reported an increase in summer and autumn herbage production by allowing some reproductive development during spring, followed by a period of hard grazing at the time of anthesis when seed heads are immature and still palatable (late control), through effects on tiller population and size. The objectives of this study were to (i) evaluate whether the benefits of late control can be measured within the management constraints of a self-contained spring calving dairy production system, (ii) investigate the conditions under which late control spring grazing management can be implemented, and (iii) investigate the options available for the use of additional feed over spring and summer assuming late control spring grazing management is effective. A dairying systems study at No 4 Dairy Unit, Massey University was set up in which two 20-paddock perennial ryegrass/white clover dominant farmlets of 45 hectares were each stocked with 120 spring calving Friesian cows in October 1993 and run for three lactations until May 1996. With the exception of spring grazing management and spring supplement feeding the farmlets were balanced. The first treatment, designated early control (EC), involved strict control of grazing throughout the spring and summer with average pasture cover targeted at approximately 2000 kg DM ha-1 and a post-grazing residual of approximately 1500 kg DM ha-1. Pastures in the second treatment (late control - LC) were allowed to develop some reproductive growth through October and November for removal in December. Average pasture cover target was 2700 kg DM ha-1, with a post-grazing residual of approximately 2000 kg DM ha-1 over spring. Average pasture cover was reduced to 2000 kg DM ha-1 in December by grazing to lower residuals while at the same time removing paddocks from grazing for immediate conservation. Bayesian smoothing provided an alternative to analysis of variance (ANOVA) for those variables where both treatments and/or all replicates were not measured at the same point in time, and for large data sets and produced mean values close to those that would be produced by conventional analysis methods without the need to group arbitrarily. The development of a dynamic rising plate meter calibration equation which accounts for seasonal differences in pasture density allowed clearer definition of herbage mass estimates from rising plate meter measurements. Mass per unit height values showed a distinct seasonal pattern reflecting changes in the sward. The bulk density of pasture in the summer was found to be twice that in the winter. Overall, there was no extended period of difference between early control and late control in either pasture production or animal production during the three years of the trial. However, large differences in animal performance would not be expected considering the marginal differences in pasture production achieved. While treatment differences in average pasture cover and pre- and post-grazing cover were achieved over late spring in all three years, the pasture cover differences required for the late control treatment were not achieved, and as a consequence the response in animal performance was smaller than the results of previous small-plot and paddock-scale experiments suggested. The results of the trial showed good internal consistency between production components and good control of variability was achieved in this large systems trial, providing an objective basis for evaluation. A number of the variables (clover contents and tiller densities) measured during the trial suggest the potential for contrast in system performance between early control and late control. The ability of the system to buffer changes contributed to the difficulties in achieving treatment specifications. Systems research of this type needs to include tight specifications and control of pre- and post-grazing pasture cover in addition to average pasture cover. More flexibility in stocking rate or use of supplements may be needed to establish spring pasture cover contrasts in future studies. A whole farm simulation model (UDDER) was used to investigate alternative management strategies for utilising grazed and conserved herbage, after modifications to achieve effective matching between predicted and measured levels of pasture production and animal performance. The level of milk production predicted by UDDER was not achieved in the field over three years using the same inputs, possibly due to the inability of the model to cope with the limitations of colder/wet winters and wetland dairy farming. The adjustments made to the parameters of UDDER were in general successful, allowing daily and annual milksolids production to be modelled. However, herbage intake was insensitive to higher spring pasture covers and resultant increase in allowance. For most of the year UDDER predicted the herbage intake of lactating cows to be at or near their potential. Early control and late control base models were used to evaluate alternative management strategies for using the extra herbage accumulation generated under the late control management, including feeding conserved forage during summer to lactating cows or during winter to dry cows, stocking rate (2.6, 2.8 and 3.0 cows ha-1) and the level of conservation (none versus increased). The loss of quality associated with conservation meant that conserving and adding silage back into the system did not increase milksolids production or gross margin, particularly when UDDER predicted that no real feed shortage existed. However, in practice conserving herbage reduces the risk associated with poor growing years. The low stocking rate policy was the best for early control, although the stocking rate policy with 2.8 cows ha-1 and conserved supplements being fed back to lactating cows in summer was similar. The latter policy was the best for late control. At the high stocking rate the flexibility of the system was reduced. In general, milksolids production and gross margin were higher for late control than early control, provided the increase in herbage accumulation rate associated with lax spring grazing management (late control) was factored in. Since a search of the literature failed to identify a model capable of predicting the response of pastures to late control spring grazing management, an attempt was made to develop a tiller-based model to allow the late control system to be investigated further. The model developed estimates equilibrium tiller density based on size or mass of ryegrass tillers at the environmental ceiling leaf area based on daily levels of photosynthetically active radiation. However, there was insufficient detailed sward data available to provide conclusive evidence for the validity of the tiller model. Despite the lack of consistent treatment differences obtained from the trial and the difficulties experienced when modelling late control management alternatives, this project has provided a comprehensive data set and considerable insight into the dairy production system. Late control spring grazing management can potentially increase the overall productivity of the seasonal dairying systems of New Zealand. In practical terms the main requirement is for a change in conservation management over the spring period, with no other direct costs involved. However, the timing limitations which are an inevitable consequence of rotational grazing systems restrict the opportunity to impose late control management with the rigorous timing that component research suggests may be necessary. During the course of this trial spring grazing management on dairy farms has tended towards that of late control management, with farmers operating grazing systems with higher average pasture covers through the spring with the aim of improving per hectare production through per cow performance.Item Systems, component, and modelling studies of pasture-based dairy systems in which the cows calve at different times of the year : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2000) García, Sergio CarlosThe New Zealand's dairy system is characterised by a concentrated calving period in late winter-early spring, which aims to synchronise cows' feed requirements with the seasonal pattern of pasture growth, but which also results in an uneven distribution of milk supply to the factories. Changing the calving season of some herds from spring into autumn could improve the overall efficiency of the dairy industry. However, pasture-based autumn-calving systems are usually perceived to be less "efficient", because of the lack of synchrony between feed supply (grazed pasture) and feed requirements. One conclusion of the literature review (Chapter 1) was to hypothesise that autumn- and spring-calving systems would perform at similar levels provided that sufficient supplementary feed was available during wintertime. This thesis integrated three experimental approaches (system, component, and modelling) in order to test the above hypothesis, and to investigate the physical performance of pasture-based dairy systems that differed in their calving dates. A 3-year system study conducted at No 1 Dairy Farm, Massey University, in which autumn, spring, and autumn/spring calving systems were compared, showed that all systems achieved similar performances and overall efficiencies (Chapter 2). A key factor for this was the greater total yields by the autumn-calved cows, due mainly to their greater yields in mid and late lactation and their longer lactations (Chapter 3). A new technique that combines the n-alkanes and 13C methods in order to quantify herbage and maize silage DM intakes by individual grazing cows which are given access to the silage as a group, was developed and validated (Chapter 4), and re-evaluated in a separate study (Chapter 5). Overall, individual cows differed considerably in their intakes of maize silage DM, but this variation was not always related to variation in milk yields. An innovative, dynamic, interactive simulator of seasonal pasture-based dairy farms (IDFS) was developed as part of this thesis (Chapter 6). The model allows computer experiments to be run, with pastures and cows managed on the basis of logical decision rules; therefore, it resembles real farm management. The user makes decisions (which paddocks are to be grazed, pre- and post-grazing herbage mass, supplement feeding, etc) continuously, and can see the impact of his/her management decisions on the graphical interface provided. Based on comparisons with actual data, it was concluded that IDFS simulates the main components of seasonal dairy farms with reasonable realism (Chapter 7), although the model is at an early stage of development and has not been completely validated. In conclusion, this thesis has 1) demonstrated that pasture-based systems with contrasting calving dates can achieve similar physical performances provided that supplementary feeds are available, and 2) developed two new tools (quantification of herbage and maize silage intakes by individual cows, and the IDFS model) that can be applied in future systems research.Item The effectiveness of on-farm control programmes against wildlife-derived bovine tuberculosis in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University(Massey University, 2001) Sauter-Louis, CarolaIn New Zealand the Australian brushtail possum (Trichosurus vulpecula), introduced in the middle of the 19th century, is the main wildlife reservoir for Mycobacterium bovis infection for farmed livestock and other wildlife species. Thus, control of tuberculosis (TB) has to involve both livestock and vector animals. Areas with endemic wildlife infection constitute 23% of New Zealand's land area. Vector control is mainly performed by large scale poisoning operations, by both aerial and on-ground baiting, conducted by official agencies, such as Regional Councils. The costs of vector control rose from NZ$18 million in 1995 to NZ$28 million in 1998/99, and finances are not available to cover all areas with endemic wildlife infection. There is a need for farmers to be involved and participate in TB control to complement the official control efforts. This thesis comprises a number of studies that looked in detail at on-farm control measures that could be applied at farm level, their efficiency and cost-effectiveness, in order to determine if and how farmers could take on-farm measures which would complement the official TB control programme. In an initial survey of 27 Wairarapa herd managers, whose cattle herds were TB infected, 'grounded theory' was used to identify factors related to farm management and TB infection in cattle. Most farmers had knowledge or suspicion about potential high risk areas on their farm, where cattle were more likely to become infected with TB. Farms that grazed cattle in paddocks with TB hot-spot areas had a greater herd TB incidence than farms that excluded cattle from such areas, and used adjacent paddocks. Grazing management was found to be flexible, more so on beef farms than on dairy farms. These results formed the basis for designing on-farm control measures. A subsequent intervention study used 67 Wairarapa farms. On-farm control measures were implemented for three years on 34 randomly selected 'focused control' farms. On-farm control measures included targeted vector control in spring and autumn, and adoption of grazing management in summer and winter that excluded cattle from TB hot-spots during these times. These measures were implemented by the research team during the first two years and farmers continued the control work in the third year. At the end of three years the effect of the interventions was evaluated. Focused control farms achieved more effective TB control than standard control farms. They were significantly less likely to have multiple TB animals per year, a higher proportion of focused control farms came off Movement Control, and the two-year cumulative TB incidence was reduced more on focused control farms than on standard control farms. Part of the project was also to compare the Wairarapa project with a contemporary intervention study. The study was conducted on a national scale in four separate areas of New Zealand by a national organisation, using 35 focused control and 70 standard control cattle/deer farms. Farmers were advised by a multi-disciplinary team on possible management changes and vector control for two years. The implementation of these measures was the responsibility of the individual farmers. Three and a half year after the start of the project the effectiveness was evaluated as part of this thesis. Focused control farms reduced the two-year cumulative TB incidence more than standard control farms. Comparison with the Wairarapa project indicated that the hands-on operational approach of the Wairarapa project had advantages over the 'advice only' approach in the national project. All farmers involved in the two intervention studies were surveyed at the end of the intervention studies using a questionnaires, asking about farm management and TB related issues. Only the Wairarapa focused control farmers were interviewed during the project period. Only slight differences existed in these variables between focused and standard control farms in each of the projects, indicating that the allocation of farms to the two farm groups was adequate. Questions were also asked about attitudes towards TB and its control. Overall farmers rated the importance of TB eradication as very high. However, the majority of farmers were not in favour of stricter Movement Control regulations, removal of compensation or having to pay TB testing costs directly. Many farmers saw organisations, such as Government and Regional Council, as being responsible for eradicating TB and did not see any need to conduct control programmes themselves. An economic analysis of the adoption of on-farm control measures was conducted using deterministic, stochastic and decision analysis. Under the current compensation level of 65% for TB test positive animals, the adoption of on-farm control measures generally was beneficial to dairy farms, but for beef farms only if they achieved TB free herd status. Reducing the compensation level to zero did not alter the situation significantly. The net gain in dairy farms increased, the situation in the beef breeding farms changed minimally and on beef finishing farms the adoption of control programmes became beneficial if the number of TB animals was reduced at least by two, without achieving TB free status. The final stage of the project described in this thesis was the development and use of FarmORACLE, a whole-farm simulation model, that allows the user to combine knowledge about TB and its occurrence on farms with farm-specific grazing strategies. The model was used to compare traditional grazing strategies with alternative strategies, that excluded cattle and deer from grazing TB hot-spot paddocks during high-risk times. Four farms were described in detail. In all four farms an alternative grazing strategy was found that resulted in higher production or greater economic returns, while protecting the herd against exposure to tuberculous possums.