Imported genetic material of the Holstein-Friesian breed from overseas (OS), mainly from North America, has been used in New Zealand (NZ) since the late 1960's. This has diluted the genetic base of the former NZ Friesian genotype selected under intensive seasonal pasture-based systems. As a result, increased concerns have been raised about the negative influence of these overseas genes on the modern NZ Holstein- Friesian, as it is apparent that the OS Holstein-Friesian has a lower capacity to perform on grazed pasture. The objective of the present thesis was to investigate differences in production performance between three Holstein-Friesian genotypes farmed at different feed allowances (FA) on pasture-based systems; in addition, to investigate differences in the grazing process between strains under contrasting managements and sward conditions, and so to identify animal and pasture factors that affect the herbage intake (DMIH) and performance of the grazing cow. An accurate procedure was also established to estimate DMIH for cows fed forage and maize supplements, grazing in groups. Two modern high breeding worth (BW) Holstein-Friesian strains from NZ (NZ90) or overseas (OS90) origin and a low BW 1970's NZ Friesian genotype (NZ70) were farmed in two field experiments: (1) a long-term 'system' study that compared the yield performance of these genotypes in a range of systems with different feed allowance (FA) per cow, and a (2) a short-term 'component' study that compared the grazing capacity of the strains under contrasting sward conditions but at a common daily herbage allowance. The differences in productive performance between genotypes increased as the study progressed in the system study, with the largest observed in the last season. The mean milksolids (MS) yield per cow and per hectare were higher in NZ90 (395 kg cow-1 and 1,236 k ha-1) than in the NZ70 (336 kg cow-1 and 1,093 kg ha-1) and the OS90 (377 kg cow-1 and 1,154 kg ha-1). The higher production of NZ90 cows was supported by their higher mean daily MS yield than the NZ70 (1.45 vs. 1.21 kg MS cow-1 day-1) and more days in milk than OS90 cows (271 vs. 257 DIM). The lower lactation length of the OS90 strain occurred due to its lower body condition score (BCS) in late lactation, which determined an early dry-off for these cows. The lowest BCS of OS90 at the nadir (irrespective of FA), during lactation and at dry-off indicate these cows mobilised greater amount of body reserves and partitioned most of the energy ingested to yield. Genotype by FA interactions for milk and lactose yields, protein content in the milk and BCS were observed in the second and third seasons of the 'system' study. Milk yield increased as FA increased to a greater extent in OS90 than in the two NZ strains, whereas the content of solids in milk, particularly protein, increased to a greater extent for NZ90 than in both OS90 and NZ70. During lactation DMIH was higher for NZ90, intermediate in OS90 and lower in NZ70 (14.5, 13.9 and 12.6 kg DM cow-1 day-1 respectively for NZ90, OS90 and NZ70, as measured with nalkanes), and declined as lactation progressed, with a smaller difference for the total intake achieved (15.5, 15.2 and 13.1 kg DM cow-1 day-1 respectively) due to the increased supplement consumption. These results indicate that the OS90 needs more feed with a higher proportion of supplement in the diet to improve productive performance on pasture-based systems; the NZ90 would perform better when cow nutrition is mainly supported by grazing pasture, although further increments in performance could be expected from strategic supplementation, but requiring more feed than NZ70. The DMIH per unit of live weight (DMIH/LW) was highest in NZ90 strain in both the 'system' and in the short sward of the 'component' study (31.5 and 31.1 g DM kg-1 DM in NZ90 vs. 28.9 and 28.6 g DM kg-1 DM for OS90 in 'system' and 'component' studies respectively). The higher intake of NZ90 on pasture was sustained by a higher capacity to graze short swards than NZ70 and OS90, and to deal with the herbage of higher bulk density and lower quality present at the base of taller swards. The NZ90 can maintain DMIH in swards with different structures, indicating higher flexibility to perform under different managements and sward conditions. The size of the jaw is smaller in NZ90 than OS90 (88.4 vs. 92.4 mm) with effects on bite area and bite size, and this flexibility to adapt the size of the bite to swards of different structure may improve bite penetration under constraining sward conditions. The reduced ability of the OS90 to adjust ingestive behaviour to different swards would limit the capacity of this strain to perform on pasture. The fact that OS90 cows increased DMIH and DMIH/LW substantially in a leafy and taller sward (up to 21.6 kg cow-1 and 40.8 g DM kg-1Lw vs. 19.2 kg cow-1 and 41.0 g DM kg-1Lw in NZ90 during early lactation) suggests that yield performance can be improved in these cows even on pasture, by fine-tuning pasture management.

This thesis sets out to identify physical and physiological differences between lambs of different birth ranks at birth, and to use this information to identify practical on-farm management strategies which could improve triplet-born lamb survival. Triplet-born lambs, especially the lightest-triplet-born lambs, not only had a greater capacity to lose heat but also had a reduced capacity to produce heat when compared to twin-born lambs. Due to their lighter birth weights, triplet-born lambs had lower plasma thyroxine (T4) concentrations within the first 24 hours of life than twin-born lambs, and within twin- and triplet-born litters, the lightest- and medium-triplet-born lambs had greater plasma lactate concentrations than all twin-born lambs and the heaviest-triplet-born lambs. Independent of lamb birth weight, triplet-born lambs had lower plasma tri-iodothyronine (T3) concentrations within five minutes of birth, and within twin- and triplet-born litters, the lightest- and medium-triplet-born lambs had lower plasma T4 and T3 concentrations within five minutes of birth than all twin-born lambs and the heaviest-triplet-born lambs. It was hypothesised that because triplet-born lambs had a lighter birth weight and lower plasma thyroid hormone concentrations, they would have inadequate thermoregulatory capabilities when compared to twin-born lambs. The lower rectal temperatures of triplet-born lambs within the first hour of life and the lower heat production on a per lamb basis at 24 to 36 hours of age, and the lack of difference in maximum heat production on a per kg of birth weight basis at 24 to 36 hours of age support this hypothesis. Two practical on-farm management strategies trialled in this thesis to improve triplet-born lamb thermoregulation were offering concentrate supplement during late pregnancy to improve lamb birth weights, and maternal iodine supplementation to improve lamb plasma thyroid hormone concentrations. While offering concentrate showed positive effects such as increasing lamb birth weights, colostrum uptake and triplet-born lamb heat production on a per kg of birth weight basis, the results were either inconsistent across experiments or between birth ranks suggesting additional work is required to determine the repeatability and cost effectiveness of these findings. Maternal iodine supplementation offered no iv | P a g e benefits in terms of lamb birth weights, plasma thyroid hormone concentrations or lamb heat production. Further investigations identified that lamb birth weights, thyroid hormone concentrations, glucose and NEFA concentrations are positively associated with maximum heat production at 24 to 36 hours of age. Practical on-farm management strategies which could target these physical and physiological factors may improve triplet-born lamb heat production, and therefore the survival rates of triplet-born lambs.

Two field grazing experiments were conducted in New Zealand (NZ) in spring (Experiment 1; November 2008) and autumn (Experiment 2; April 2009) to evaluate the effects of feeding a high sugar perennial ryegrass (HSG; cv. AberDart; derived in the United Kingdom; UK) versus a NZ- derived control grass (cv. Impact) on milk production and estimated nitrogen (N) partitioning within the cow. Areas of both ryegrasses were replicated and sown with or without white clover (cl) (HSG+cl, control+cl, HSG and control). A cross-over design with four 10-day periods was used in each experiment, using 15 Friesian cows per treatment per period in Experiment 1 and 5 cows per treatment per period in Experiment 2. Treatment effects upon pasture botanical and chemical composition, cows’ milk yield and composition, and estimated N partitioning were studied. Nitrogen partitioning was calculated using indirect methods. Herbage concentrations of water soluble carbohydrates (WSC) were lower in autumn than in spring whilst crude protein (CP) concentrations were higher in autumn. Organic matter digestibility (OMD) and metabolisable energy (ME) concentration was similar in both seasons. There were no differences in the concentration of CP, WSC and dry matter (DM) among treatments in Experiment 1. The HSG+cl treatment had the lowest concentrations of neutral detergent fibre (NDF, 417 g/kg DM) and the highest content of ME (12.6 MJ/kg DM) and tended to have the lowest sward dead matter content compared with the other three treatments. In Experiment 2 both HSG treatments showed higher concentrations of WSC (15 g/kg DM) compared with the control, both with and without clover; the concentrations of NDF and acid detergent fibre (ADF) were the lowest for both HSG treatments. In Experiment 1, cows grazing treatments with white clover produced more milk (1.6 kg/day) and more milk solids (MS; 0.16 kg/day) than cows grazing pure ryegrass swards ( P< 0.01), with highest milk yields being from cows grazing the HSG+cl treatment (ryegrass cultivar x white clover interaction P<0.05). No differences in milk production were found in Experiment 2. Estimated urinary N excretion (g/day) was similar for all treatments in both seasons, although N intake differed among treatments. The proportion of N intake excreted in urine or secreted in milk was similar for all treatments in both experiments. Nitrogen output (g/day) in milk was the highest for the HSG+cl treatment in Experiment 1 but no differences were found in Experiment 2. Data were combined from both experiments to study the effects of the herbage CP:WSC ratio upon estimated N partitioning between milk and urine. Mean ratios were 0.72 for spring herbage and 2.27 for autumn herbage. As the amount of WSC increased in the diet relative to the amount of CP (thus a lower CP:WSC ratio) there was a significant increase in the amount of milk N secreted per unit of N intake in spring but not in autumn. The breakpoint in the relationship between the herbage CP:WSC ratio and the nitrogen utilisation efficiency for milk production (NUEm) was 1.32, and the NUEm for that breakpoint was 14 g milk N per 100 g N intake. Ratios below this point were associated with improved efficiency of converting pasture N to milk N; ratios above this point were not correlated with changes in N conversion efficiency. It is concluded that the CP:WSC ratio in perennial ryegrass may be important in the partition of absorbed N into milk or urine. A NZ-selected HSG with a lower CP:WSC ratio is likely to have major benefits for pastoral farming in NZ. In order to be effective, a NZ-derived HSG should substantially increase WSC concentration in autumn pasture (from approximately 100 to 200 g/kg DM) whilst reducing CP content simultaneously (from 240 to 190 g/kg DM). The lower structural fibre and higher milk production for the HSG+cl treatment in both experiments suggest that under NZ conditions, best productive responses to HSG may be obtained in management systems that include white clover.

Studies of humans and domestic animals have shown that there is a linkage between the neonatal and post-natal health of an individual and its uterine environment during gestation. However, very little information exists for sheep and there have been no studies that have directly examined the stage of gestation at which such effects could be introduced to the conceptus. In the present study, pure-breed embryos were transferred within and reciprocally between large (Suffolk: S) and small (Cheviot: C) breeds of sheep to establish different uterine environments; SinS (large control), SinC (restricted environment), CinS (luxurious environment) and CinC (small control) and their effects upon embryonic, fetal, neonatal and post-natal development and glucose metabolism of lambs were examined. By Day 19 of gestation, conceptuses (embryo and trophoblast) developing in a restricted uterine environment (SinC) were smaller (P<0.05) than in control (SinS). The head length of SinC fetuses was smaller (P<0.05) than in SinS fetuses on Day 55 of gestation and SinC lambs were lighter and smaller (P<0.05) than SinS lambs at birth. During subsequent post-natal life, there was no difference (P>0.05) in the growth rate of SinC and SinS lambs. The liveweight and body dimensions of SinC lambs were lower (P<0.05) than SinS lambs until 9 weeks and 12 weeks of age, respectively. Day 19 peri-implantation embryos and trophoblasts that developed in a luxurious environment were bigger than in control (CinC). However, CinS fetal size did not differ (P>0.05) from CinC fetuses by Day 55 of gestation. There was no difference (P>0.05) in the birthweight and body dimensions of lambs born from these two groups. Dimension of the placentas of SinC and SinS or CinS and CinC did not differ (P<0.05) during gestation or at lambing. Concentrations of ovine placental lactogen (oPL), progesterone, insulin-like growth factor-1 (IGF-1), glucose and free fatty acid (FFA) differed between uterine environments. During glucose challenge tests, there were no differences in the concentrations of glucose and insulin, between SinC and SinS female lambs, however, glucose concentrations declined more rapidly (P<0.05) in CinS than CinC female lambs at one year of age. It was concluded that restricted uterine environment affects embryonic, fetal and neonatal development of lambs, and that these effects perpetuates until at least one year of age; but there was no effect upon glucose metabolism. Conversely, a luxurious uterine environment enhances the early development of embryos but had no effects upon subsequent fetal, neonatal and post-natal development; however glucose metabolism of post-natal female lambs was improved. It appears that these effects of uterine environment were mediated through the trophoblast during the early embryonic period and via the placenta during subsequent gestation. oPL, progesterone, IGF-1, glucose and FFA were implicated in feto-maternal dialogue. These results suggest that uterine environment significantly influences the biology of young sheep with possible economic consequences.

Five rotational grazing experiments were carried out at Massey University's Riverside farm, in the Wairarapa, on the East Coast of the Southern North Island, New Zealand, to compare the effects of feeding Lotus corniculatus L. (birdsfoot trefoil; cv. Grasslands Goldie) or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) dominant pasture upon sheep year round productivity. These studies also investigated under grazing, seasonal and annual net herbage accumulation rate and seasonal dynamics of undisturbed (i.e. non-grazed) net herbage accumulation rate of L. corniculatus relative to that of grass-dominant pasture. Aspects of in vivo digestibility of dry matter (DMD), organic matter (OMD), digestible organic matter in the dry matter (DOMD) and metabolisable energy (ME) concentration of L. corniculatus at different stages of maturity over the spring, summer and autumn were investigated in three indoor digestion trials. 1. Two field experiments (Chapter 2) were conducted during spring to assess the effects of grazing mixed age undrenched ewes on L. corniculatus (n = 50) or pasture (n = 50) and their lambs (mainly twins) on live weight (LW), wool production, faecal nematode egg count (FEC) and dag score. In Experiment 1 (18 October 2000 to 21 January 2001) and Experiment 2 (3 October 2001 to 2 January 2002) both forages were fed ad libitum. Total condensed tannin (CT) concentration in the diet selected was 24 to 27 g CT/kg DM for L. corniculatus and 1.4 to 1.5 g CT/kg DM for pasture. The LW gain, weaning LW and wool production were consistently greater (P < 0.001) for lambs grazing L. corniculatus, in either Experiment 1 (258 vs. 189 g/day; 36.1 vs. 30.1kg; 1.17 vs. 0.98 kg) and in Experiment 2 (247 vs. 162 g/day; 31.8 vs. 24.1kg; 1.17 vs. 0.81 kg), respectively. Ewe and lamb dag scores were strongly and positively correlated with dag weight (P < 0.001) and generally increased with time in sheep grazing pasture, whilst grazing on L. corniculatus consistently reduced dag score. FEC in ewes grazing pasture showed a post-parturient rise (PPR) following lambing, whilst ewes grazing L. corniculatus had a reduced PPR in FEC. Up to day 70, FEC in lambs grazing L. corniculatus was lower than that for lambs grazing pasture, but between day 70 and the end of both experiments (approximately day 90), FEC in lambs grazing L. corniculatus increased to similar values as for pasture-fed lambs. FEC was not correlated with dag score or dag weight in ewes or lambs grazing pasture, but these indices were weakly and positively correlated in ewes and lambs grazing L. corniculatus, suggesting that lowering FEC on L. corniculatus also reduced dag formation. It was concluded that under dryland farming conditions, the use of L. corniculatus during the spring/early summer lactation period can increase lamb LW and wool production, whilst eliminating the need for pre-lambing anthelmintic drenching and probably reducing the amount of insecticide needed to control flystrike. These effects compared to pasture are probably due to higher digestibilty, higher ME concentration, higher voluntary feed intake (VFI), and to the effect of CT in reducing rumen protein degradability and controlling internal parasites in sheep grazing L. corniculatus. The absence of endophyte in L. corniculatus may have also have contributed to these effects. 2. During 2001 and 2002 (Chapter 3), grazing trials from February to November were conducted for 279 days (Experiments 1) and 285 days (Experiment 2), to compare the effects of grazing shorn mixed age Romney ewes in light condition on L. corniculatus versus pasture during the mating period (9 weeks, Experiment 1) and 11 weeks (Experiment 2). In Experiment 2, the length of time (days) that ewes need to graze L. corniculatus before mating to maximise reproductive performance was also investigated. Common objectives in both Experiments were to measure forage feeding effects on ewe wool production and LW of their lambs at weaning. In Experiment 1, groups of ewes (n = 100) were fed on either L. corniculatus or pasture at a herbage allowance of 1.8 kg green DM/ewe/day for the first three weeks of feeding and increased to ad libitum (2.3 kg green DM/ewe/day) during the mating period for two cycles. In Experiment 2, groups of 75 ewes grazed L. corniculatus for 42, 21, 10 and 0 days before a synchronised oestrus, with pasture being grazed for the balance of the 42 days. All L. corniculatus groups continued grazing L. corniculatus for a further 5 weeks. Feed allowance was initially 2.0 kg green DM/ewe/day, increased to 2.3 kg green DM/ewe/day during the mating period over the two cycles. At the end of L. corniculatus feeding in both experiments the groups were combined and grazed on pasture until weaning. Total CT concentration in the diet selected was 18 to 29 g CT/kg DM for L. corniculatus, with only trace amounts in pasture. In Experiment 1 mating ewes on L. corniculatus compared to pasture increased number of lambs born and lambs weaned per ewe lambing by 16 and 32% units respectively (P < 0.05), due to more multiple and less single births (P = 0.06) and to reduced lamb mortality (P < 0.05) between birth and weaning. In Experiment 2, increasing the numbers of days of grazing L. corniculatus before ovulation (0, 10, 21, 42 days) linearly increased ovulation rate (P < 0.05), lambs born and lamb weaned by up to 16% units, but had no effect upon lamb mortality. Mating ewes on L. corniculatus increased wool production (P < 0.01) and fibre length (P < 0.05) in Experiment 1 but not in Experiment 2. Grazing L. corniculatus had no effect on lamb birth weight and only small positive effects on weaning LW. It was concluded that, under commercial dryland farming conditions, the use of L. corniculatus during the mating season in late summer/autumn can be used to increase reproductive efficiency and wool production, with the largest responses in years with exceptionally dry autumn periods. These effects are probably due to the higher digestibility and ME concentration of L. corniculatus than pasture and to the CT in L. corniculatus reducing rumen protein degradability and leading to greater essential amino acid (EAA) absorption from the small intestine. Effects of forage CT upon the uterine microenvironment at the time of conception, implantation and early foetal growth, need to be investigated in future studies. It is also suggested that effects of mating on L. corniculatus upon lamb mortality between birth and weaning should be further investigated with ewe numbers/treatment increased from 100 to 350. 3. During the summer of 2002/2003, another grazing trial (Chapter 4: 95 days) compared the effects of grazing L. corniculatus and pasture on LW and the dynamics of nematode parasite infection in Suffolk x Romney weaned lambs fed ad libitum. Half of the lambs (n = 30) grazing either L. corniculatus or pasture received oral anthelmintic at the start and at monthly intervals (regular-drenched groups), whilst the remaining 30 lambs in each treatment only received oral anthelmintic when mean faecal nematode egg counts (FECs) exceed 1,000 eggs/g wet faeces (trigger-drenched groups), which occurred on day 58 only for both groups. Trigger and regular-drench lambs grazed separate areas. Total CT concentration in the diet selected was 40 to 31 g CT/kg DM for L. corniculatus, with only trace amounts in pasture. Regular-drenched lambs grazing L. corniculatus had significantly higher LW gain (298 g/day) and carcass weight gain (133 g/day) than all the other groups, whilst trigger-drenched lambs grazing L. corniculatus had significantly greater LW gain (228 g/day) and carcass gain (99 g/day) than regular-drenched (200; 66 g/day) and trigger-drenched (187; 63 g/day) lambs grazing pasture. Carcass fatness was significantly lower for trigger-drenched lambs than for regular-drenched lambs, when fed either L. corniculatus or pasture. Dag score was consistently lower for regular-drenched lambs grazing L. corniculatus than pasture; trigger-drenched lambs showed similar effects up to day 48, with no differences between the two groups thereafter. Regular anthelmintic treatment maintained FECs at low values, while parasitised lambs on L. corniculatus tended to have higher FECs than pasture-fed lambs. Relative to trigger-drenched lambs that grazed pasture, grazing trigger-drenched lambs on L. corniculatus had significantly reduced worm burdens of Haemochus contortus, Teladosargia spp., Nematodirus spp. and Cooperia spp. at slaughter, but greater burdens of Trichostrongylus spp., Chabertia ovina, Oesophagostonum spp. and Trichuris ovis were present in L. corniculatus-fed lambs. It was concluded that grazing L. corniculatus under dryland farming conditions compared to pasture can increase LW gain of weaned lambs, whilst reducing reliance on anthelmintic drenches to control parasites. These effects are probably due to increased protein supply from the action of CT enabling the lambs to have a higher LW gain when carrying a parasite burden, and to L. corniculatus better maintaining its high ME value under drought conditions. Using L. corniculatus to finish weaned lambs without anthelmintic drenches for a seven-week period is proposed. 4. A three-year study (Chapter 5; November 2000 to October 2003) was conducted to compare, under grazing conditions, seasonal and annual grazed net herbage accumulation rate and seasonal dynamics of undisturbed (i.e. non-grazed) net herbage accumulation rate of L. corniculatus relative to grass-dominant pasture. Prediction equations to estimate standing DM in L. corniculatus and pasture from the rising plate meter (RPM) and sward surface height were also generated. L. corniculatus and pasture growing in a moderate fertility and low-pH soil (pH 5.35) accumulated similar total herbage masses (24.3 vs. 24.1 t DM/ha) over the 3-year period, with the DM production being greater for L. corniculatus than for pasture during 2000-2001, producing more DM during summer/autumn drought conditions. The net herbage accumulation rate from undisturbed areas of L. corniculatus and pasture were similar in spring, summer and autumn. Seasonal variation in the calibration regressions fitted to estimate herbage mass of L. corniculatus non-destructively, suggested a combination of destructive and nondestructive methods are needed to assess herbage mass. It was concluded that L. corniculatus has the potential to increase the performance of a pasture-based sheep dryland farming system due to its ability to grow in acidic soils, its tolerance of drought conditions during summer/autumn and its seasonality of feed supply. 5. Three digestion experiments involving cryptorchid weaned lambs were conducted for 14 days over the spring, summer and autumn to determine changes in in vivo digestibility of DM, OM, digestible OM in the DM and ME concentration of L. corniculatus at different stages of maturity. In vivo digestibility samples were then used as standards to investigate if the enzymatic in vitro system of Roughan and Holland (1977) could predict OMD and DOMD of CT-containing L. corniculatus. Digestibility of L. corniculatus declined as it matured, but the rate of decline was much less than occurs for temperate grasses and for white clover. It was concluded that the in vitro enzymatic system of Roughan and Holland (1977) can be used to predict OMD and DOMD of L. corniculatus, provided a standard curve involving in vivo data generated with L. corniculatus is used. Using a standard curve with in vivo data from pasture led to bias which increased at lower OMD values. Reasons for the consistent differences between L. corniculatus and pasture standard curves are discussed, including possible effects of residual bound CT in lowering in vitro digestibility. From this series of experiments, this study is the first to report that relative to conventional perennial ryegrass/white clover, mating ewes on L. corniculatus under grazing conditions may reduce post-natal lamb mortality. It is also the first study to show that grazing sheep on L. corniculatus can maintain productivity during spring and summer with reduced dependence on anthelmintic drench input. It is concluded that whole farm modelling, mechanical harvesting and conservation strategies, selection of L. corniculatus germplasm for creeping-type plants more suited to grazing and the integration of new crops containing secondary compounds, such as chicory, should be considered to support major advances in sustainable dryland sheep farming systems.

The Salado region of Argentina covers 9.5 million ha, is located in the centre-East of the Buenos Aires Province, and concentrates about 6.9 million cattle. Cow-calf systems are predominant in the area. A simulation model was developed with the purpose of assisting in the design and evaluation of cow-calf systems in the Salado Region. The model was designed to produce long term simulations of the dynamic interactions between herd structure, climatic variation and farm management over periods of several decades using daily weather data, real or simulated. Existing models were used to describe soil, pasture and animal components of the farm, linked with management actions in a dynamic framework. The model was driven by decision rules entered by the user, which allowed the representation of management options that respond to changing farm conditions according to a predetermined policy. An object-oriented approach (OOA) was used in the design and implementation of the model. In the OOA, objects in the real world (e.g. cows, paddocks) are represented as objects in the computer program. The simulation of individual cows and individual paddocks made it possible to distribute feed resources flexibly among animals and provided many other points of flexibility in management strategies. The management strategies simulated in trying to improve cow-calf systems in the Salado region were based on Reserva 6, an experimental cow-calf farm located at the INTA-Balcarce Experimental Station. Every spring-summer, 30% of the area is devoted to make low quality hay (by cutting at high herbage mass), most of which is destined to provide maintenance feed for pregnant adult cows in winter. Cows are kept on a small paddock from weaning (March) to calving (August-September), during which time they receive 6-9kg DM of hay per day. A set of decision rules was developed to represent (on a 100ha farm) the management applied in Reserva 6 and, using this as a base system, a series of simulation experiments was conducted. Firstly, three preliminary experiments, aimed at gaining insight into the system and testing the model, were carried out. In the first of these, the effect of delaying the breeding season 15 and 30 days was analysed. The model was run over 30 consecutive years using a real weather sequence, 1970-2000, from INTA-Balcarce, for each scenario. It was found that, when the appropriate management variables (i.e. weaning and sale dates) were adjusted accordingly, changing the calving period had little effect on the productivity of a cow-calf system. In the second experiment, the dynamic consequences of three different heifer replacement policies on the production outcomes of the system were explored. The policies produced different patterns of oscillations in key farm outputs as a result of periodic behaviour in the age structure of the herd, and the differences between strategies were shown to be dependent on the environmental variability being simulated. The third experiment analysed different policies for hay use during the autumn-winter period, including a control strategy in which no hay was harvested or used. The results suggested that, provided hay was utilized on the farm, the pattern of use did not make much difference to liveweight production. Secondly, the long term performance, in terms of annual liveweight sold, of a range of hay quantity-quality combinations was compared. Each policy was simulated across a range of cow numbers (170 to 350, cows plus heifers in a 100ha farm) and was replicated 20 times. Each replication consisted of 50 years of random weather sampled from the real sequence (1970-2000). The benefit of using hay and the contrasts between the effects of different haymaking strategies on animal outputs increased as the cow numbers increased. The long term analysis suggested that the liveweight production of cow-calf farms, under a calendar-based haymaking policy like that followed in Reserva 6, would be maximized by harvesting 40-50% (but not more) of the total farm area and aiming to harvest hay at medium herbage mass (therefore medium quality). Therefore, the policy currently followed in Reserva 6 of allocating 30% of the farm to haymaking could be considered as conservative, and its productivity might be increased by making hay at lower herbage mass. Thirdly, the possible advantages of incorporating flexibility into the haymaking policy used in Reserva 6 were evaluated using the same experimental design. The results indicated that controlling haymaking in a flexible fashion, basing the decisions of closing, releasing and cutting paddocks on a simple pasture budget, would give the system productive advantages (i.e. increases in productivity and reductions in variability) in relation to a calendar-based approach. Using a flexible haymaking policy allows the manager to make more hay than required for the next winter, providing a buffer for the system. A flexible haymaking policy permitted significantly greater levels of herbage utilization by making large amounts of hay without negative effects on the carrying capacity of the system. A preliminary analysis of risk and costs highlighted major advantages in using hay in cow-calf systems, especially when a flexible approach to haymaking is implemented.

A series of grazing experiments was conducted, in the summer/autumn of 2001, 2002 and 2003, to investigate the effects of poplar (Populus spp.) and/or willow (Salix spp.) supplementation, during mating, on ewe production and reproduction when grazing drought pasture. Each experiment involved a rotational grazing system with 300 mixed-age Romney ewes, divided into three groups of 100 ewes each. In each year, all ewes were offered low quality simulated drought pasture, containing more than 60% dead matter, at an allowance sufficient to provide a potential desired intake of 0.70 kg dry matter (DM)/day, for periods of 9 to 12 weeks, including two mating cycles. Mean pre-and post-grazing pasture masses averaged over the three years were 1100 and 600 kg DM/ha. The pasture consumed in all years was typical of pasture available to grazing livestock in a drought; it was high in neutral detergent fibre (NDF; approximately 600 g/kg DM), low in organic matter digestibility (OMD, approximately 0.52) and metabolisable energy (ME; approximately 7.5 MJ/kg DM) and contained approximately 20 g nitrogen (N)/kg DM. The supplementary poplar and willow diets were always superior to drought pasture consumed by the ewes, being higher in OMD (approximately 0.67), ME (approximately 10 MJ/kg DM) and total N (approximately 26 g/kg DM) and lower in NDF (approximately 383 g/kg DM). Tree fodder diets also contained substantial concentrations of the secondary compounds condensed tannin (CT; range 7 to 52 g/kg DM), salicin (approximately 2 g/kg DM) and other phenolic glycosides (approximately 21 g/kg DM), with willow (27 to 52 g/kg DM) containing greater concentrations of CT compared with poplar (7 to 19 g/kg DM). Mean diameter of the tree fodder stem consumed during the series of experiments was approximately 7 mm for poplar and 4 mm for willow with the diameter increasing over the experimental periods in four cases out of live (P<0.05). After the supplementation period, the three groups were joined together and grazed on perennial ryegrass/white clover pasture until the conclusion of each experiment at weaning. In all years, the effect of poplar and/or willow supplementation on ewe live weight (LW) and body condition score (BCS) change; the proportion of lambs (reproductive rate) at pregnancy scanning, lambing, docking and weaning; and wool production and staple length from ewe fleeces with approximately 11 months growth, were measured. Experiment 1 was designed to determine how much poplar fodder needed to be fed to increase ewe production and reproduction over a 71-day supplementation period. The experiment involved a high supplementation group, offered 1.5 kg fresh poplar/ewe/day; a low supplementation group, offered 0.75 kg fresh poplar/ewe/day; and a control group that was offered no tree fodder. Ewes in the high and low treatments lost less LW (-67 and -71 vs. -82 g/day; P<0.05) and BCS (-0.78 and -1.27 vs. -1.31 units; P<0.05) compared with unsupplemented ewes. Reproductive rate was relatively low in the control group (121 lambs born/100 ewes mated), with poplar supplementation increasing ewe reproductive rate by approximately 20% units (P<0.05) and 30% units (P<0.001) for the low and high treatment groups, respectively, at scanning, lambing, docking and weaning. The increase in reproductive rate in supplemented ewes was due to increases in both conception rate (number of ewes pregnant/100 ewes mated) and fecundity (number of lambs born/100 ewes mated). Experiment 2 was designed to determine if production and reproduction varied between ewes fed poplar versus willow at the same rate of supplementation, 1.4 kg fresh forage/ewe/day, for 87 days. Again, reproductive rate was relatively low in the control group (133 lambs born/100 ewes mated), with willow supplementation reducing L.W loss (-86 g/day vs. -103 g/day; P<0.01) and increasing reproductive rate by 15%, 17% 21% and 20% units at ultrasound scanning (P=0.097), lambing (P=0.087), docking (P<0.05) and weaning (P=0.058), respectively. The increase in reproductive rate was due to an increase in fecundity; supplementation did not affect conception rate in this experiment. Unlike the previous experiment, poplar supplementation showed no effect on reproductive rate, despite the increase in DM intake and the apparent reduction in LW loss of 9 g/day (P-0.11). It is likely that severe contamination of the poplar fodder with Melampsora larici-populina, or poplar leaf rust, confounded the results. Building on the results of the first two grazing trials, the next step was to determine the period (days) of tree fodder supplementation necessary to achieve a response in reproductive rate. Experiment 3 involved ewes fed 1.3 kg fresh willow/ewe/day for a 'long' period, 63 days including 6 weeks of mating, and a 'short' period, 31 days including 3 weeks of mating. The mating period commenced on the same day for all groups and lasted for 6 weeks. Willow supplementation for 63 days reduced ewe LW loss (-96 g/day vs. -147 g/day; P<0.05) and BCS (-0.79 VS. -1.09; P<0.05) loss, compared with unsupplemented ewes; however, it did not increase reproductive rate at scanning and lambing. The lack of response in willow-supplemented ewes was likely to be due to toxic concentrations of zearalenone (1.5 mg/kg DM), an oestrogenic mycotoxin, in the drought pasture during mating, which confounded the results by negating any potential benefits due to increased nutrient intakes. Willow supplementation for 63 days did increase reproductive rate at weaning by 13% units, due to a 9% unit (P<0.05) reduction in post-natal lamb mortality, from 17.1 to 8.4%. Supplementation for 31 days did not appear to influence ewe reproduction and production parameters. Overall, the rate of LW loss was greater in Experiment 3 compared with the first two experiments. Seven indoor in vivo digestibility experiments were conducted at the following times; early April 2001 (poplar), February, March and April 2002 (all poplar), and December, March and April 2003 (all willow). Each 14-day trial involved 6 male cryptorchid lambs, individually fed in metabolism cages. The experiments showed that the digestibility of poplar and willow tree fodder declined from late spring to autumn (P<0.05), but that the decline was much smaller than the decline in digestibility of grass-based pastures in New Zealand over the same time period. The experiments also showed that mean ME and digestibilities were generally higher for willow than for poplar. The seven in vivo digestibility coefficients were then used to develop a standard curve for in vitro prediction of in vivo digestibility, this standard was used to analyse all unknown tree fodder samples from the three grazing experiments. Results from the three grazing experiments showed that supplementing ewes grazing drought pasture during mating with poplar and willow tree fodder consistently increased DM intake by 0.25 to 0.33 kg DM/ewe/day for ewes offered 1.3 to 1.5 kg fresh willow or poplar each day and increased calculated total DM intakes from 0.67 to 1.03 kg DM/ewe/day in Experiment 1, from 0.59 to 0.86 kg DM/ewe/day in Experiment 2 and from 0.47 to 0.75 kg DM/ewe/day in Experiment 3. Supplementation also consistently reduced LW loss and loss in BCS and substantially increased lambing rate through increased conception rate and fecundity and reduced post-natal lamb mortality. The effects on LW and BCS gradually declined in the post-treatment period and were no longer evident by commencement of lambing. There was no effect of supplementation on wool production or staple length in any of the experiments. One of the unexpected results of the experiments was an average 34% reduction in post-natal lamb mortality over three years, due to willow/poplar supplementation of ewes during mating. Initial results showed that despite significant increases in fecundity in supplemented ewes in 2001 and 2002, post-natal lamb mortality was not increased. This result, combined with a statistically significant reduction in lamb mortality in Experiment 3 (P<0.05), in the absence of any differences in fecundity between the groups, suggested that tree fodder supplementation during mating may have reduced lamb mortality in all three years, but that the effect was masked by the increase in reproductive rate in the first two experiments. Therefore, data from the three field trials were combined and analysed by adjusting all mortality data to equal birth rank and sex; this showed a significant reduction due to supplementation (P<0.05) with no treatment-year interaction. The increase in ewe production and reproduction in supplemented ewes was likely due to increases in nutrient intake, through increased DM, ME and CP intakes, prior to and during mating and to increased outputs of undegradable dietary protein and microbial protein from the rumen, per unit of crude protein consumed, thus increasing amino acid absorption. An increase in ovulation rate of 1.5 % units/MJ of digestible energy consumed (Smith 1985) should result in increases in ovulation rate due to tree fodder supplementation of only 5 and 4% units in 2001 and 2002, respectively; however, the increases in scanning rate were substantially greater at 41 and 16% units. Therefore, it is possible that the majority of the increase in reproductive rate was due to increased essential amino acid absorption, which is consistent with increases found in ewes mated on CT-containing forages such as Lotus corniculatus (Birdsfoot trefoil). Gross margin analyses using actual data from unsupplemented ewes in each of the three grazing trials compared with Riverside Farm's commercial ewes from the same years showed that drought reduced scanning rates by an average of 22.4% and wool production by 20% and that this reduction decreases sheep production income by approximately $14/ewe. Further analysis showed that almost half the cost ($6/ewe) could be recovered by supplementing ewes with tree fodder in a drought. On a whole farm basis this represents $58/hectare cost benefit due to tree fodder supplementation. Fungal contamination was a significant factor in the results obtained in Experiments 2 and 3. In all years, simulated drought pasture contained metabolites of zearalenone and the trichothecenes nivalenol and deoxy-nivalenol, produced by Fusarium fungi, while in Experiment 2 the poplar was severely contaminated with Melampsora larici-populina, or poplar leaf rust. Zearalenone concentrations in pasture were at their greatest in Experiment 3 and increased to over 2 mg/kg DM during the mating period. This may explain the lack of increase in reproductive rate expected in willow-supplemented ewes in Experiment 3, which was a feature of previous experiments; however, it did not explain the much greater loss in ewe LW in Experiment 3. Nivalenol (NIV) and deoxy-nivalenol (DON) are common trichothecene toxins found in New Zealand pasture and were found in pasture samples from all three experiments, however, the concentration in Experiment 3 was three- to four-fold greater than in previous experiments. Reports have suggested that trichothecenes may be partly responsible for the reduced growth of otherwise healthy livestock grazing dry autumn pasture, often referred to as 'ill thrift'. However, based on evidence from dosing experiments, it is unlikely that the quantities of NIV and DON present in pasture in Experiment 3 accounted for all of the greater LW loss seen in this experiment. This suggests that these toxins are likely to be indicators of other more potent fungal toxins, which have a much bigger impact on livestock health and production. It is likely that fungal toxins contribute more to reduced reproduction in breeding ewes and to ill thrift in young stock grazing dry autumn pastures in East Coast regions than is currently acknowledged

A positive phenotypic correlation between milk protein percentage and reproductive performance in dairy cattle, especially during early lactation has been recently reported. The objective of this study was to quantify the relationship between milk protein percentage and different measures of fertility in Irish, seasonal calving, dairy cattle using data from experiments comparing strains of Holstein-Friesian cows under different feeding systems. The relationships between body condition score, milk production and fertility were also investigated. The data used in this study consisted of 584 lactation records over a 5-yr period. Principal component analysis and logistic regression was used to study the relationship between milk protein percentage and fertility performance of the cow. Greater milk protein percentage during the first 60 days post-calving was associated with better reproductive performance. The probability of a cow being submitted in the first 21 days of the breeding season increased with increased milk protein percentage during early lactation. Similarly, the probability of a cow becoming pregnant to its first service or to the whole breeding season also increased. Cows were classified as either high or low milk protein percentage based on their protein percentage over the whole lactation. Cows in the high milk protein group had a 7% greater conception rate compared to cows in the low protein percentage group. In conclusion, cows with higher protein percentage, especially during early lactation are submitted earlier in the breeding season, and have a higher conception rate. Physiologically, the shortage of glucose caused by negative energy balance restricts the synthesis of milk protein in the udder. On the other side, negative energy balance also causes the reduction of IGF-I, LH and oestradiol, which consequently delay the ovarian follicular development and finally reduces fertility. Therefore, there is a biological explanation for the association between milk protein percentage and fertility performance.

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2018-10-05T17:30:59Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dailiene_costa_martins.pdf: 912491 bytes, checksum: 33139be95a4396938cbad99798e74ac2 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2018-10-05T19:51:28Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dailiene_costa_martins.pdf: 912491 bytes, checksum: 33139be95a4396938cbad99798e74ac2 (MD5) / Made available in DSpace on 2018-10-05T19:51:28Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dailiene_costa_martins.pdf: 912491 bytes, checksum: 33139be95a4396938cbad99798e74ac2 (MD5) Previous issue date: 2018 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Os sistemas de integra??o s?o modelos de produ??o sustent?veis que visam melhor uso dos recursos naturais e insumos, gerando maior diversidade de produtos para o produtor rural aumentar sua renda. Estes sistemas s?o mais complexos, pois agregam o componente agr?cola, pecu?rio, e, tamb?m, o florestal em uma mesma ?rea, exigem maior controle do manejo das forrageiras e intera??es com o ambiente, que t?m efeito na produ??o de produtos de origem animal. Objetivou-se avaliar as caracter?sticas da pastagem e o desempenho produtivo de bovinos da ra?a Nelore, em dois sistemas de integra??o, ILP e ILPF, nas esta??es de ver?o e inverno. O experimento foi conduzido na Embrapa Gado de Corte, Campo Grande-MS, em ?rea experimental com dois sistemas, um de integra??o lavoura-pecu?ria-floresta (ILPF) com 227 ?rvores/ha de Eucalyptus urograndis e outro de integra??o lavoura-pecu?ria (ILP) com ?rvores nativas remanescentes, ambos com pastagens de Brachiaria brizantha cv. BRS Piat?. O delineamento experimental utilizado foi o de blocos completos ao acaso em esquema de parcelas subdivididas, em que as parcelas consistiram em dois sistemas de integra??o (ILP e ILPF) e, as subparcelas, nas esta??es do ano (inverno e ver?o). A produ??o de massa seca (PMS) de forragem foi maior no ILP (3.412 kg/ha) que no ILPF (2.308 kg/ha). Para o ganho de peso vivo (GPV) e o ganho m?dio di?rio, n?o foram encontradas diferen?as significativas (P>0,05) entre os tratamentos ILP 238,6 kg/ha; 475,4 g/cab. dia) e ILPF (268,7 kg/ha; 581,4 g/cab. dia). O desempenho animal n?o foi prejudicado pela menor massa seca de forragem no ILPF, na esta??o de ver?o. Os valores de prote?na e DIVMO da folha foram maiores no ILPF. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Zootecnia, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2018. / Integrated systems are sustainable production models that aim at better use of natural resources, generating greater diversity of products for the rural producer to increase their income. These systems are more complex, since they add the agricultural component, livestock, and also the forest in the same area, require greater control of forage management and interactions with the environment, which have an effect on the production of animal products. The objective of this study was to evaluate the forage production and animal performance of Nellore cattle in two integrated systems, ICL (integrated crop-livestock) and ICLF (integrated crop-livestock-forestry) in summer and winter season. The experiment was perfomed at Embrapa Gado de Corte, Campo Grande - MS, in an experimental area with two integrated systems, crop-livestock-forest (ICLF) with 227 trees/ ha of eucalyptus urograndis and crop-livestock (ICL) with 5 remnant native trees, both with pasture of Brachiaria brizantha cv. BRS Piat?. The experimental design consisted of two complete integration systems (ILP and ILPF), and the subplots, in the seasons (winter and summer). Forage dry matter production (PMS) was higher in ILP (3,412 kg / ha) than in ILPF (2,308 kg/ ha). For the live weight gain (GPV) and average daily gain, no significant differences (P> 0.05) were found between ILP treatments 238.6 kg/ ha; 475.4 g/ cab. day) and ILPF (268.7 kg/ ha, 581.4 g/ day). Animal performance was not affected by the lower dry mass of forage in the ILPF, in the summer season. The protein and IVDOM of leaf were higher in ILCF.

As pastagens naturais são a base alimentar para grande parte da pecuária de corte no Rio Grande do Sul, ainda que este ambiente seja susceptível a variações climáticas estacionais que afetam o crescimento da vegetação, quais sejam as baixas temperaturas de inverno e deficiência hídrica no verão. A fim de minimizar os efeitos deletérios proporcionados à vegetação por períodos climáticos desfavoráveis, a presente dissertação tem por objetivo avaliar o efeito de duas estratégias de diferimento na produção animal e vegetal de uma pastagem natural da região fisiográfica da Campanha. O trabalho foi desenvolvido na Embrapa Pecuária Sul, localizada no município Bagé, onde foram avaliados duas épocas de diferimento: primavera (DP) e verão-outono (DVO) e um tratamento testemunha sem diferimento (SD), durante dois anos. O delineamento foi inteiramente casualizado, com medidas repetidas no tempo (ano) e três repetições de área por tratamento. Foram utilizados novilhos da raça Braford em lotação continua com carga variável de forma a manter uma oferta média de forragem de 10 kg MS/100 kg de peso corporal/dia. A taxa média de acúmulo de pasto e a produção liquida de forragem foi semelhante entre tratamentos, com médias de 14,7 kg MS/ha/dia e 4648 kg MS/ha/ano, respectivamente. Já a massa média de forragem foi 27% superior nos tratamentos com diferimento. Com relação à produção animal, o primeiro ano permitiu taxa de lotação média 14% superior ao segundo ano e, na média dos anos o diferimento de primavera foi 21% superior aos demais. O ganho médio diário e a produção animal por área apresentou interação entre ano de avaliação e tratamento, sendo observado maiores GMD no primeiro e segundo ano para SD e DVO, com média de 0,321 e 0,340 kg, respectivamente. De uma forma geral o que explica essa interação é a diferença no número de dias que os animais permaneceram pastoreando cada tratamento e a estrutura da pastagem pós período de diferimento. As estratégias de diferimento não apresentaram superioridade na produção de pasto frente ao tratamento testemunha devido a ocorrência de condições climáticas anormalmente favoráveis nos anos avaliados. Ainda assim, o diferimento de primavera no primeiro ano e de verão-outono no segundo ano, apresentaram desempenho semelhante ao tratamento sem diferimento, mesmo estes apresentando um período de pastoreio consideravelmente menor. / The natural pastures are the main food resource for most portion of the beef cattle in Rio Grande do Sul, even though, this environment to be susceptible to seasonal climatic variations that affect vegetation growth, namely the low winter temperatures and water stress in summer. In order to minimize the deleterious effects provided for vegetation by unfavorable climatic periods, this thesis aims to evaluate the effect of two deferral strategies in animal and plant production of natural pasture in the Campanha physiographic region. The study was conducted in Embrapa South Livestock located natural in the municipality Bagé, where were evaluated two deferral periods: spring and summer-autumn, and a control treatment without deferral, during two years of treatment application. The design was completely randomized with repeated measurements over time (year) and three replications per treatment. Braford steers were used in continuous stocking with variable load in order to maintain an average forage allowance of 10 kg DM/100 kg Life Weight per day. The accumulation forage average rate and the net forage production was similar between treatments, with averages of 14.7 kg DM/ha/day and 4648 kg DM/ha/year, respectively. The average forage mass was 27% higher in treatments with deferral. Regarding to animal production, the first year had an average stocking rate 14% higher than the second year and the average of the years the spring deferral was 21% superior to the others. The average daily gain and animal production by area showed interaction between year of assessment and treatment, being observed greater average daily gain in the first and second year for without deferral and summer-autumn deferral, averaging 0.321 and 0.340 kg, respectively. In general way which explains that interaction is the difference in the number of days that animals were grazing each treatment and the structure of pasture at post deferral period. The deferral strategies did not show superiority in the production of pasture in front of the control treatment due to non-occurrence of normal adverse weather conditions in the evaluated years. Still, the spring deferral in the first year and the summerautumn deferral in the second year showed similar performance to treatment without deferral, even these having considerably less grazing period.