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Pasture management to minimise the detrimental effects of pre-lamb shearing : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University, New Zealand
(Massey University, 1996) Husain, Muhammad Hamsun
The purpose of this study was to examine whether the performance of prelamb shorn sheep is influenced by pasture allowance in the immediate post-shearing period and whether the relationship between performance and pasture allowance differed according to whether the ewes were shorn by standard comb (SC) or cover comb (CC). The trial was replicated across two years to allow for climatic variations that occurred between seasons which could markedly affect results. Fifty four ewes were used in each year in a 3x3x2 factorial design with three shearing treatments (ST) (SC, CC, and unshorn), three sward surface height (SSH) (nominal 3, 5, and 7 cm) and two pregnancy-status treatments (single and twin). There was an interaction between ST and SSH which resulted in liveweight gains during the period from pregnancy day 115 (P115) to P135 of 275, 613 and 4518 g; 1557, 2314 and 3997 g; and 3623, 2894 and 3997 g for SC, CC and unshorn (control) ewes set-stocked on 3, 5, and 7 cm SSH, respectively. There were no effects of ST or SSH on lamb weaning weight, ewe wool growth rate or mean fibre diameter. There was no interaction between ST and SSH for lamb birth weight (LBW), but the LBW of lambs bom to SC ewes (4.9±0.1 kg) was significantly heavier (P<0.05) than those of lambs born to unshorn (control) ewes (4.3 ± 0.1 kg). Rectal temperatures of SC or CC ewes were significantly lower (P<0.05) than those of unshorn (control) ewes on day 2 following shearing (S2), and on S4, S8, and S20. Pasture allowance, however, did not affect rectal temperatures of shorn ewes. Blood concentrations of glucose, NEFA or 3-OHB were not influenced by ST or SSH throughout the days of measurement. There were no effects of ST or SSH on ewe organic matter intake (OMI), except on the 2nd day following shearing where the OMIs of ewes set-stocked on 3 cm (941±147 g) were significantly lower than those ewes grazing 5 cm (1628± 101 g) or 7 cm (1349±135 g) SSH pasture. The results suggested that hypothermia, as determined by rectal temperatures and induced by pre-lamb shearing, cannot be avoided by pasture management. Neither the use of a standard comb for pre-lamb shearing, nor a low pasture allowance (3 cm SSH) affected short- or longterm production parameters.
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 P
With 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.
Systems modelling in animal production research : an interactive case study : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
(Massey University, 1982) Miller, Campbell Petrie
Synthesis of improved systems of year round dairy herd feeding requires whole systems to be assembled and evaluated. In the field, only a limited number of possibilities can be examined and it is likely that there will be interaction between systems and the unique environments in which they are necessarily set. Modelling was undertaken to enlarge the possible number of syntheses and to provide a constant environment in which they could be compared. A number of forage sources and a variety of milk production patterns were combined in a linear programming model which maximized economic or physical returns from combinations of forage supply and demand, within constraints of pasture and crop management, cow intake and forage quality. The linear programming model was validated, firstly by exposing details of structure and output to an expert panel and secondly, by comparing model structure and output with those of several real farms. Experiments were carried out in which cropping level, stocking rate, conservation level, cow production level and forage yield and quality were varied. Selected systems were subjected to simulated climatic variability and milkfat price variability to test the stability of preliminary conclusions. It was shown clearly that the main thrust of the field research, feeding for higher production per cow, was likely to be both feasible and highly profitable. Most of the potential means for facilitating this were shown also to be feasible and economic, though there were limitations which had not previously been obvious. Nitrogen fertilizer on pasture was shown to be potentially very valuable. Schedules for nitrogen use in practice would require much better definition of response patterns and the modelling lent weight to decisions regarding research in this area. High quality, wilted, pasture silage was shown to be an essential component of systems without maize silage where high production (160 kg milkfat per year) per cow is required. Preliminary evaluation of a summer-growing grass showed large potential benefits and supported an increase in the effort to develop such a grass for commercial use. Several other forage crops were shown to have value. Somewhat surprising was the finding that grazing these crops was often a more profitable and productive means of utilization than conservation, despite inferior efficiencies in dry matter utilization. This was due to the higher cost of conservation allied with lower quality. Maize silage was a particularly valuable forage source and it was shown how efforts to increase its yield or energy density, but not its protein content, would be rewarding. It was concluded that the interaction of modelling and field research had been valuable in both development and testing of hypotheses. Suggestions are made for more formality in validation, for greater continuity in parallel modelling and for more generality in field data collection.
Application of intraruminal chromium controlled release capsules to the measurement of herbage intake of sheep at pasture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
(Massey University, 1990) Parker, Warren James
Experimental evidence obtained since 1950 suggests that New Zealand sheep farm production and financial returns could be increased by adopting separate grazing management for ewes of different pregnancy and rearing status from 6 weeks before lambing until weaning. Progress in developing management systems for the differential allocation of pasture, favourable lambing paddocks and labour during this period has been restricted by the absence of equipment for diagnosing ewe pregnancy status and a lack of data relating pasture conditions to feed intake and ewe and lamb productivity. Accurate pregnancy diagnosis by realtime ultrasound scanning has been available to farmers since 1985, but research into ewe grazing management continues to be hampered by the absence of techniques for measuring feed intake. This thesis addressed the latter issue, first by validating controlled release capsule (CRC) technology for measuring feed intake and second by examining feed intakes of ewes differing in pregnancy and rearing status and relating intakes to productivity. A series of 11 experiments were conducted with sheep CRC to validate this technology for measurement of intake and to develop appropriate systems for using the technology in experimental situations. These studies examined: the linearity and period of Cr2O3 release; the effect of presence of capsules in the rumen on voluntary feed intake; the effect of feed type and feeding level on Cr2O3 release rate; and the accuracy of faecal Cr2O3 concentration in predicting faecal output of sheep dosed with CRC when alternative sampling regimens were applied. These experiments, conducted under both indoor feeding and outdoor grazing conditions, established that CRC released Cr2O3 into the rumen in a uniform manner once initiation of matrix extrusion had been completed 2 to 3 days after capsule insertion. The subsequent period of linear release (25 to 100 days) was found to be primarily dependent upon characteristics of the capsules controlled at manufacture (i.e. orifice diameter, matrix composition and length of pressed tablet matrix core). In comparison, environmental factors, both within and outside the sheep, had relatively small effects on the rate or linearity of Cr2O3 release. Release rate decreased by c. 4% if daily feed intake was at 0.7 maintenance compared to an ad libitum level, increased by c. 2% if hay rather than fresh pasture was consumed and decreased by 10 to 13% if capsules were placed in rumen-fistulated sheep rather than in intact animals. Adoption of feeding level below 0.6 maintenance for 4 to 7 days reduced Cr2O3 release rate and could cause capsule failure. Between-capsule variation in release rate from CRC recovered from the rumen by slaughter was low (coefficient of variation 2.0 to 6.5%). Variation between capsules within sheep was usually lower still. Voluntary herbage intake was significantly reduced if sheep were dosed with prototype CRC with inflexible wing designs. Under indoor conditions, correlations of 0.90 to 0.99 between daily faecal output derived by Cr2O3 dilution and actual faecal output for individual sheep were obtained. The correlation between estimates of mean 3-day faecal output of sheep at pasture predicted from the Cr2O3 concentration in morning and evening grab samples and from total collections was 0.87. Prediction of individual animal intakes (indoors) appeared less accurate (r = 0.74) because of variation in capsule release rate and in the animal's own ability to select and digest its diet. Group mean estimates, which are appropriate for practical grazing conditions, were usually within ± 10% of the actual value. Low diurnal variation in faecal Cr2O3 concentration (non-significant) allowed flexible faecal sampling regimens to be applied. In summary CRC were demonstrated to be superior to existing feed intake measurement techniques and to be well suited to the estimation of mean intakes of sheep, provided that suitable faecal sampling regimens were applied. A pilot study investigating the feed intakes and productivity of ewes of different pregnancy and rearing status indicated that intakes of twin-bearing ewes were reduced in comparison to those of single-bearing ewes during late pregnancy, when the two groups were grazed together under "commercial" farming conditions. During lactation, intakes exhibited a curvilinear relationship with time and were generally higher (by up to 32%) in twin-rearing ewes than in single-rearing ewes. This pattern of feed intake was less clear in a subsequent nine-week lactation study. In that trial, experimental groups comprising equal numbers of ewes rearing single or twin lambs were continuously grazed on five different pastures maintained at fixed sward surface heights (2.5, 4.0, 6.0, 7.0 and 9.0 cm). Herbage intakes by both single- and twin-rearing ewes were maximised at a sward surface height of approximately 5.0 cm (1000 to 1100 kg dry matter/ha). Lamb growth rates were not affected by sward height during the first six weeks of lactation because the ewes mobilised body reserves to maintain milk production. All ewes lost liveweight during the first 6 weeks of lactation but only the ewes on the 2.5 cm sward failed to regain lost liveweight from weeks 6 to 9 of lactation. Wool production, strength and colour were not affected by sward conditions in either the ewes or lambs over the lactation period. These results suggest that New Zealand farmers would gain little benefit from differential management of ewes post-lambing where a minimum grazing height of 5.0 cm could be maintained provided that ewes were in good condition (i.e minimum condition score 3.0) at lambing.
Studies on the digestion of ryegrass species and the regulation of food intake by sheep : a thesis submitted for the degree of Doctor of Philosophy in the Massey University of Manawatu
(Massey University, 1964) Ulyatt, M. J.
The economy of New Zealand is dependent largely on the export of products of the livestock industry. While there has lately been an upsurge in secondary industry, a basic lack of raw materials and cheap labour curtails New Zealand's ability to compete economically with other countries as a manufacturing nation. If New Zealand's position as one of the world's leading agricultural exporters is to be maintained or expanded then increased primary production must be achieved. Such an increase is also necessary to maintain or improve the high standard of living of a rapidly growing internal population. Three general factors are important when the problem of increasing livestock production is considered. 1. Nutrition 2. Breeding 3. Diseases and Pests The interest of the author lies with nutrition but the other two factors are clearly important if animal production is to be improved. Breeding is important particularly in relation to raising fertility and producing types of animals that will give optimum returns in particular environments. It must be remembered however, that genetic improvement by selection of livestock, though essential, is usually slow because of the low heritability of many productive characteristics. Pests and diseases can limit animal production, particularly at high stocking rates, so the prevention of epidemics and the eradication of persistent diseases such as footrot, brucellosis and tuberculosis must continue to be actively pursued. At a symposium entitled, "Problems of Increasing Sheep Production", held in February 1964 by the NewZealand Society of Animal Production, it was evident that the most effective short-term method of increasing animal production would be by increasing stocking rate. This infers increases in both animal numbers and the food to support them. Thus to increase the carrying capacity of the present farming area there must be an increase in the quality and quantity of pasture produced. This can be achieved in two ways: by techniques of pasture management and by breeding improved strains of pasture plants. It must also be remembered that considerable advances may be obtained with improved management of existing strains of pasture plants.
Seasonal variation of pasture quality on commercial equine farms in New Zealand : a thesis in partial fulfilment of the requirements for the degree of Master of AgriScience (Equine Studies) at Massey University, Palmerston North, New Zealand
(Massey University, 2011) Hirst, Robyn Lesley
The equine production system in New Zealand is largely pasture-based and as a result broodmares, foals and young horses acquire a significant percentage of their nutrition primarily from pasture. The reliance on pasture as the main nutrient source in New Zealand is in distinct contrast to the more intensive equine production systems found in other countries such as in Europe and North America. However, there is increasing scientific evidence that raising horses primarily on pasture may provide the optimal environment for the development of a sound and durable athlete. In addition, the supply of a balanced nutritional ration for the broodmare is important as inadequate nutrition can lead to reduced fertility. The requirement to produce a live healthy foal every year is crucial to maintaining the production cycle as mares which fail to conceive within a 25-day window post-partum eventually have to forgo a mating season which is costly to the business which relies on the sale of a young horse each year. The compositional data gathered during this study showed that equine breeding farm pastures were rarely deficient in energy, protein or fibre. The low energy content of pasture in summer and in some cases autumn was caused by high dead matter content and reproductive stem content. The presence of reproductive stem content and dead matter in the sward is linked to poor pasture utilisation, but can also be present during prolonged periods of climatic pressure (lack of rainfall). Lower nutritional quality of pasture is likely to be the main limitation to animal performance, especially in regions where summer temperature is high, rainfall is low, forage availability is reduced and the stocking density is high. During the breeding season commercial equine breeding farms experience a period of high stocking density which can be detrimental pasture quality and availability. Consideration of the recommended nutritional requirements of horses were made on the basis that there was sufficient dry matter (DM) available for the bloodstock to consume. The pasture management study found that there is an opportunity within the equine production system for improved pasture utilisation and production to allow for the provision of adequate nutrition to valuable bloodstock.
The complexing of calcium and magnesium by organic plant constituents : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy, Chemistry/Biochemistry Department, Massey University
(Massey University, 1971) Molloy, Leslie Francis
The definition, occurrence and aetiology of hypomagnesaemic tetany is discussed as an introduction to the practical implications of the present investigation. The current hypotheses, involving an unfavourable pasture chemical composition, accounting for the binding of Ca++ and Mg++ in the intestinal tract of ruminants are reviewed. The role of undigested or partly-digested plant cell wall materials is advanced as another such hypothesis, and the present investigation of the cell wall polymers of a typical pasture grass is outlined. The comprehensive analysis of the grass Yorkshire fog (Holcus lanatus) involves, initially, the extraction and purification of pectic substances, lignin, hemicelluloses and cellulose. The non-volatile organic acid content of the grass is also determined. Analytical methods are developed and evaluated in order to assess the homogeneity of these isolated cell wall fractions, and their chemical constitution investigated to aid in determining any possible relationship between cation complexing and polymer (or monomer) structure. The pectic fraction isolated from Yorkshire fog is approximately 90% polygalacturonic acid while the hemicelluloses are basically arabinoxylans with varying hexose and uronic acid content. Attempts tofractionate the predominant hemicellulose, hemicellulose B, into homogenous arabinoxylans gives inconclusive results. Most of the chemical evidence, however, indicates the presence of three discreet polysaccharides in this fraction - a simple arabinoxylan, an acidic galactoarabinoxylan and a neutral glucan. Infrared and ultraviolet spectroscopy is utilised to determine the purity of the isolated lignin as well as the presence of typical lignin functional groups. Yorkshire fog lignin has a moderate phenolic hydroxyl and -OMe content and, like most other monocotyledonous lignins, gives yields of syringaldehyde, vanillin and p-hydroxybenzaldehyde on alkaline nitrobenzene oxidation. The outstanding feature of the lignin is its appreciable content of etherified hydroxyl groups in the 4-position of the aromatic ring and the low yield of syringaldehyde. The water-soluble, non-volatile organic acids are quantitatively determined by anion-exchange resin chromatography and their identity confirmed by paper chromatography. The major acid is the tricarboxylic acid, trans-aconitic acid, which is determined spectrophotometrically. The normal plant acids, citric and malic, are present in moderate quantities while the alicyclic acids, quinic anc shikimic, are only present in minor amounts. A limited amount of data on the seasonal fluctuation of these organic fractions in Yorkshire fog is presented. Electrolytes and the concept of ionic activity are discussed in the introduction to the study of the ability of these plant fractions to bind Ca++ and Mg++ in an aqueous salt solution of cationic composition similar to that of the intestine of a ruminant. A cation exchange method is developed whereby changes in the activity of Ca++ or Mg++ on the introduction of a plant fraction into the salt solution are reflected in the cationic composition of the equilibrium resin. An investigation is undertaken of a large number of calibration solutions varying in [ca++] and[Mg++], but constant in [Na+], [K+] and [NH4+], the latter cations being present in excess as 'swamping' cations. Regression expressions relating solution cation concentration to the equilibrium resin cation concentrations are derived and used as calibration equations to determine the amounts of bound and ionic Ca++ and Mg++ in solutions in equilibrium with the plant fractions. The pectic substances, lignin and the organic acids are effective in complexing a large proportion of the solution Ca in a non-ionic form but only lignin and the organic acids display a significant complexing of solution Mg++. Except for hemicellulose B (branched) at a slightly alkaline pH, the hemicelluloses and cellulose have little ability to complex either Ca++ or Mg++. The complexing results are discussed in terms of the relationship of polymer structure to observed cation affinity. Factors involved in cation binding are: - the charge and degree of hydration of the cation itself; - distribution and degree of esterification of carboxyl groups in the polymer; - monomer conformation; - type of glycosidic linkage in the polymer; - the possibility of hydrogen-bonding and non-bonded interactions between substituents on the polymers; - solution pH. The in vivo implications of the results are finally discussed in the context of general ruminant nutrition and alkaline-earth metal absorption discussed in the introduction.
Defoliation management, tiller density and productivity in perennial ryegrass swards : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Plant Science at Massey University, New Zealand
(Massey University, 1995) Hernández Garay, Alfonso
Lax spring grazing management followed by hard grazing at the time of anthesis has been suggested as a means to improve herbage production of perennial ryegrass pastures during summer and autumn by enhancing tillering activity. However, there is little comparative information on the effects of variation in the duration of the period of lax grazing. Thus, the aims of this study were (i) to investigate the effects of timing and duration of lax spring grazing on tiller dynamics, rates of leaf growth, botanical composition and pasture production in perennial ryegrass swards, with and without white clover, and (ii) to determine which physiological and/or morphological factors are important in influencing regrowth after defoliation of such swards. Two field experiments and one glasshouse experiment are reported. In the first field experiment (September 1992 to March 1993), swards of perennial ryegrass (Grasslands Nui) with and without white clover (Grasslands Tahora) were rotationally grazed by sheep every 21 days to a residual height of 70-100 mm (lax) and every 14 days to a residual height of 30-50 mm (hard). Two periods of lax grazing (short release "SR" from 26 October to 8 December and long release "LR" from 15 September to 8 December) were compared against conventional hard grazing (early control "EC"). All treatments were grazed to a residual height of 30-50 mm every 14 days from 8 December until the end of the Experiment. Treatments were arranged in a factorial design with 3 replicates. Plots without white clover received 28 kg N ha-1 every two weeks as urea. During spring, herbage mass increased in SR and LR as a consequence of an increase in tiller weight. Leaf growth in ryegrass and white clover and sward productivity all increased after lax spring grazing, and responses were greater following LR than SR. Evidence of effects on ryegrass tiller densities were inconclusive, although tiller production appeared to be greater in SR and LR treatments than under conventional hard grazing. White clover responses were variable. In the second field experiment (September 1993 to April 1994) plots were subjected to similar grazing managements, the only differences being that all spring treatments were imposed at a consistent grazing interval of 21 days. There was also an increase in the number of replicates per treatment (from 3 to 4), and a reduction in N level (from 28 to 14 kg N ha-1 every 2 weeks). The results from this trial confirmed that SR and LR treatments, because of their greater percentage of reproductive tillers, increase ryegrass herbage production during spring by increasing tiller weight. During summer and autumn production remained high on SR and LR treatments due to enhanced tiller population density and leaf growth per tiller and/or stolon. White clover responses were variable, and in general SR and LR treatments tended to produce more leaf per locus than EC. For white clover, no statistical differences were observed in net production per unit of area (g m-2 day-1). Size/density compensation implies that at higher herbage mass, individual tillers are larger, but the population density is correspondingly decreased. To investigate the links between tiller dynamics and herbage production, and the relationship between sward height, tiller density and tiller size, an index of sward productivity (size/density compensation index, SDCI) was generated. Size/density compensation index was defined using the -3/2 self thinning relationship of plant ecology. Shoot density and tiller weight were plotted as X and Y coordinates, respectively and SDCI defined as the distance between the point plotted for a particular sward and a theoretical self-thinning line of slope -3/2. A plot of herbage production from January to April against SDCI showed a strong positive correlation between SDCI and productivity. The results indicate that the distance from the -3/2 self-thinning line, or size/density compensation line, can be used as a predictor of sward productivity. In a glasshouse experiment the effect of defoliation management on tiller size/density compensation (SDC) was studied. Under controlled environmental conditions perennial ryegrass swards growing from seed were defoliated to stubble heights of 20 mm, 40 mm, 80 mm, 120 mm and 160 mm twice a week (simulating continuous stocking) over a six month period. The results demonstrated an increase in tiller weight and a decrease in tiller population density as defoliation intensity decreased. The optimum combination of tiller density and leaf growth per tiller which maximised herbage harvested per unit time was observed at a defoliation height of 120 mm. The response of plants to defoliation was decreased total, below and above ground plant mass, gross and net photosynthesis per unit of ground area and tiller weight as the severity of cutting increased, while leaf appearance rate and gross and net photosynthesis per unit of leaf weight were increased. The use of the -3/2 self-thinning rule to describe the relationship between tiller population density (X) and individual weight per tiller (Y) was also examined. For cutting heights between 40 mm and 120, the size/density relationship had a slope steeper than -3/2. For defoliation heights above 120 mm SDC slope was closer to 1.0. However, slope corrections for change in leaf area index (Ca) and leaf:non leaf ratio (Cr) largely explain observed deviations from the theoretical -3/2 size/density compensation line. Again, the plot of herbage harvested against SDCI showed strong positive correlation between the two. It is concluded that lax spring grazing management of ryegrass-white clover swards (70 to 100 mm) followed by hard grazing (30-50 mm) at the time of anthesis enhances pasture production, particularly during the summer-autumn period, by increasing both tiller population density and net leaf growth per tiller and/or stolon. Effects were larger following an extended spell of lax grazing (12 weeks) than following a shorter spell of 6 weeks. Size/density compensation index was shown to be a predictor of sward productivity, sward productivity having a strong positive correlation with SDCI.
Response of chicory (Cichorium intybus L.) to defoliation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, New Zealand
(Massey University, 1997) Li, Guangdi; Li, Guangdi
Chicory (Cichorium intybus L.) is a perennial herb which has long been used as a forage crop. However, only recently has this species been re-evaluated in terms of its agronomy and animal performance. The objectives of this research were to study the persistence and the seasonal patterns of herbage mass accumulation and morphological development of forage chicory under defoliation. A series of field and glasshouse experiments were conducted at the Pasture and Crop Research Unit (PCRU), the Deer Research Unit (DRU) and the Plant Growth Unit (PGU), Massey University, Palmerston North, New Zealand (latitude 40°23'S) from 1993 to 1996. 'Grasslands Puna' chicory was used in all experiments except for one of the glasshouse experiments (Chapters 6 and 7) where two contrasting cultivars, 'PG90' and 'Orchies', were also included. Under grazing, Puna chicory accumulated herbage masses of 8.5, 9.4 and 4.6 t dry matter (DM)/ha from November to April, with average plant densities of 66, 69 and 24 plants/m2 and plant sizes of 2.9, 2.7 and 6.7 shoots/plant, for 1,2 and 4 year old stands, respectively (Chapters 3, 4 and 5). It was concluded that the characteristics of a grazed chicory crop that had deteriorated to the point of not being able to accumulate half of its maximum herbage mass were 25 plants/m2, six or more shoots/plant, or less than 150 shoots/m2. Defoliation stimulated the development of secondary shoots, but suppressed the growth of the primary shoot. Axillary shoots, however, developed fully regardless of whether or not plants were defoliated. The main source of feed from chicory for livestock was primary leaves during spring, and secondary and axillary leaves during summer and autumn (Chapters 4, 6 and 7). Results from both field and glasshouse experiments suggested that Puna chicory was more sensitive to defoliation frequency than intensity. It was concluded that defoliation at 50-100 mm in height at 3 week intervals in spring, and at 100-150 mm at 5 week intervals in summer and autumn, maximised the leaf formation and minimised the stem development of chicory. Grazing decreased the plant density of chicory regardless of grazing intensity or frequency, with the significant decrease in late spring and early summer when primary shoots were controlled (Chapters 3 and 4). Autumn grazing, especially hard grazing, was detrimental to plant persistence (Chapters 4). It was concluded that less grazing pressure through the growing season cannot be used to improve persistence without compromising leaf growth rate, but that avoidance of grazing in late autumn will improve the persistence of chicory. In a comparison of three cultivars, Orchies was the most persistent cultivar but had the slowest growth rate, and PG90 was the least persistent but with the highest growth rate, whereas the performance of Puna was intermediate, due to their contrasting root sizes and different root carbohydrate reserves. It was suggested that to improve the persistence and enhance the leaf production of Puna by plant breeding the emphasis should be on increasing taproot size without unduly prejudicing herbage mass accumulation.
Field and modelling studies of the effects of herbage allowance and maize grain feeding on animal performance in beef cattle finishing systems : a thesis 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, 2004) Machado, Claudio Fabián
The objetive [sic] of the work described in this thesis was to develop a mathematical model designed as a tool for research intended to improve the efficiency of finishing systems for 1-2 year old beef cattle under intensive grazing mangement [sic] on sown pastures in Argentina. The work involved a) three experiments in Argentina carried out to define the effects of herbage allowance and maize grain supplementation on herbage intake and animal performance, b) one experiment in Argentina following a preliminary study in New Zealand of seasonal variation in the composition and nutritive value of intensively managed beef pastures, and c) an exercise to develop a model of beef cattle production incorporating modules dealing with aspects of pasture production and utiisation [sic], herbage intake and animal performance. The results from the series of short-term grazing studies showed consistency in the comparison of the effects of increasing herbage allowance and supplementation on herbage intake and animal LWG (Chapter 4). A method combining the use of n-alkane and 13C method proved to be accurate for quantitative estimates of herbage and maize grain intake, and allowed estimates of a substantial variation in individual maize grain intake (between 31 to 41 % CV) when animals are supplemented in groups. The substitution rate (SR) measured in these studies varied little across experiments or level of grain at a herbage DM allowance of 2.5 % LW d-1 (0.36 and 0.38 kg herbage DM per kg grain DM for Chapters 3 and 4 respectively). Increasing level of herbage DM allowance increased quadratically the SR from 0.38 to 0.83 and 0.87 kg herbage DM per kg grain DM. The n-alkane method was effective in providing estimates of diet digestibility. Different methods for estimating diet composition, such as microhistological evaluation of faeces, differences in nutrient and component selection indexes and n-alkanes were used in the initial grazing trial (Chapter 2) but they were not considered to be reliable and they were too laborious for continued use under field conditions. The outcome of the studies on seasonal variation in herbage quality initially was useful in establishing a database of the range of values observed, and in demonstrating their relative robustness, at least under conditions of good pasture management. In these studies, herbage nutritive value did not seem to be a limiting factor for growing beef cattle, at least in terms of the minimum observed content of metabolisable energy (10.8 MJ ME kg DM) or crude protein (17.3 % DM). Additionally, significant relationships were established between morphological and maturity estimates and herbage nutritional variables in a pasture under grazing conditions. These relationships showed promise for future use in the prediction of herbage nutritive value, but require further work. The model developed ("BeefSim"), represents the main biological dynamic processes of the target system of this thesis, together with additional management decision and financial estimates. It was shown that the model presents adequate flexibility and can be interrogated in terms of its response to different management conditions, scenarios and timeframes. Pasture management and grain feeding were controlled in an interactive management module responding to deviations in pasture conditions and animal liveweight from pre-determined targets. Two key outcomes of the model, liveweight gain and herbage intake were accurately predicted when compared against experimental information under different levels of herbage allowance and maize feeding. System comparisons developed with the model showed agreement with the literature, and maize grain feeding associated with the monitoring procedure demonstrated an effective use of grain in the system. The model provides a good biological basis for a holistic appraisal of the effects of "process technologies" such as grain feeding in beef cattle finishing systems, and will be developed further.

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