School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemA study of weight-loss and compensatory gain in sheep( 1971)Two experiments of similar nature were conducted. In the first experiment 49 Corriedale wethers at approximately 8 months of age were allocated to four experimental groups and, within groups, to various slaughter weights which were spaced at 5 kg intervals. Group I animals were fed ad libitum and slaughtered - over a body weight- range of 38 - 63 kg inclusive. Groups II and III animals were fed ad libitum until 48 kg body weight hereupon intake was restricted to achieve a body weight loss of 0.9 kg/week until body weights were reduced to 38.5 kg and 34.5 kg, respectively. Ad libitum feeding was then resumed and animals were slaughtered up to 63 kg body weight at the same weight intervals as in Group I. Group IV animals were fed ad libitum until 48 kg body weight and then, food was adjusted to maintain body weight at 48 kg. Four animals were slaughtered after 60 days and a further four after 120 days of maintenance of body weight. In the second experiment, 15 wethers of similar age, breed and nutritional history as those used in Experiment 1, were allocated to four slaughter groups in a treatment similar to that of Group III in Experiment 1. Four animals were slaughtered at 33 kg body weight at the beginning of the first period of ad libitum feeding; three animals slaughtered at 45.5 kg at the end of the first period of ad libitum feeding; three animals slaughtered at 33.5 kg at the end of the weight loss phase; and five animals slaughtered at 46.5 kg at the end of the second period of ad libitum feeding. The compensatory growth rates of animals in Groups II and III were greater than those of Group I in each of the successive 5.5 kg increments in body weight. By maintaining higher growth rates over the entire weight range, the largest animals of Groups I I and III were slaughtered at a similar age to those, of Group I. Similarly, in Experiment 2, the compensatory growth rates (Group VI) were greater than continuous growth rates (Group V) over the body weight range used in this experiment. The data was transformed to logarithms in order to use Huxley's (1932) allometric growth equation in the linear form for an analysis of covariance. During continuous growth (Groups I and V), the empty body weight (EBW) increased as a proportion of full body weight (FEW) whilst during the compensatory growth which followed weight loss (Groups II, III and VI) the proportion of EBW remained constant. At the same FEW the EBW of Groups I I and III was less than that of Group I. Similarly, the EBW of animals maintained at a constant body weight (Group IV) was less, at the same FBW, than that of Group I. Carcass weight (CW) increased as a proportion of EBW as EBW increased in Groups I and V but the proportion remained constant in Groups II, III and VI. At the geometric mean FEW, treatment did not affect CW. However, the apparent dressing percentage (CW / FBW x 100) was 2% less during compensatory growth compared with that during continuous growth. The carcass length of animals in Groups II, III and IV was greater than that of animals in Group I.
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ItemNutritional studies with the young ruminant( 1971)This thesis outlines a study of the calcium requirements of the young lamb (Part 1) and a comparison of the nutritional efficiency of the young lamb with the young pig (Part 2). Part 1 was carried out in co-operation with Dr. N. Palmer of the Department of. Pathology, School of Veterinary Science, University of Melbourne. The section includes a review of the methods which have been used to determine the calcium requirements of animals. The experimental work involved continuous calcium, phosphorus and magnesium balance studies of lambs from about 1 to 10 weeks of age. Dr. Palmer collected blood samples, killed the animals and prepared selected bones and liver samples for analysis. He was responsible for the calcium, phosphorus and magnesium analysis of the blood and bones and for the liver copper analysis. I was responsible for the design 'of the experiment, the collection and chemical analysis of all other material and the statistical analysis of the data. The interpretation of the results and the preparation of each section (including the review) have been my responsibility. Part 2 includes a literature review on aspects of the voluntary intake of animals and data on the comparative nutritional efficiency and body composition of the young Iambs and pigs when fed reconstituted whole cows' milk. Nutritional efficiency was expressed in terms of the voluntary intake of energy, digestibility, food conversion efficiency and the percentage retention of the nitrogen and energy contained in the milk. I was responsible for all aspects of the work appearing in this section.
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ItemVariability in the intake of supplements by grazing sheep( 1979)Although the practice of feeding supplements to grazing animals is widespread through the world, its efficiency still deserves further study. Factors associated with the supplements themselves, the animals being fed, the environment, and the grazing diet being supplemented together constitute a set of variables which affects not only acceptance and intake, but also the nutritional and economic efficiencies of supplementary feeding. This study is concerned with the feeding of supplements to grazing sheep under temperate climatic conditions. Oat grain, hay and molasses-urea blocks (Barastoc, KMM Pty. Ltd., Melbourne) were used initially, but subsequent experiments were confined to the utilization of molasses-urea blocks. Only recently have researchers emphasized the importance of variability in supplement intake between individuals within a herd or flock and estimates of intake, with large ranges between animals, have now appeared in the literature. Langlands and Bowles (1976) considered that such wide variabilities in intake, limit the effectiveness of all forms of supplementation. However, little is known about the factors affecting variability in a group situation and few attempts have been made to identify the possible factors inducing such wide ranges of intakes in grazing animals. Arnold and Bush (1968) identified three types. of sheep: "shy-feeders", periodic non-feeders, and over indulgers". In some situations social dominance has been observed to affect responses to supplements (Franklin and Sutton, 1952; Wagnon, 1965; Squires and Daws, 1975) , and Arnold and taller (1974) correlated the intake of supplements with body weights of sheep. Chapter 1 of this thesis reviews the direct and indirect effects on animal performance of the main factors related to the feeding of supplements. Chapter 2 presents estimations of intake of three supplements, oats, hay, molasses-urea block, made with sheep in small paddocks. Results of behavioural observations and body measurements of the sheep are presented and discussed separately in Chapter 3. Chapter 4 provides an assessment of the acceptability of molasses-urea blocks by seven different flocks of grazing sheep on five private properties. The effects of confining sheep in yards on their acceptance of the blocks are also reported. Few studies have sought to determine whether management stratagems may improve the rate of adaptation of sheep to molasses-urea blocks and induce more uniform intakes between animals. Pilot trials described in Chapter 5 were conducted to identify possible management procedures that may be suitable for these purposes. Four such procedures were sufficiently encouraging to justify testing in a replicated experiment, which is described in Chapter 6. These treatments were imposed on sheep confined in yards and fed hay at a submaintenance levels. The investigations described in Chapter 7 utilised a different approach and are concerned with the behavioural aspects of learning, a topic which has been intensively studied with laboratory animals but only rarely with farm animals. The effects of offering molasses-urea blocks to lambs in the pre-weaning period are assessed in terms of their acceptance of blocks in later life. Inevitably only a few experimental possibilities and combinations have been assessed in the work reported in this thesis. Major attention was directed towards molasses-urea blocks because they induced wider variability in the responses by sheep than did hay or grain supplements . The blocks used were those manufactured by KMM Pty. Ltd., Melbourne, had a hard texture for protection against wet weather conditions and required animals to lick them rather than chew them. Variations in block formulation were not studied in the work described in this thesis and it remains possible that other types of block may have produced different results.
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ItemUtilization of protein and energy in growing lambs( 1970)Extensive pasture improvement throughout large areas of Australia in recent years has emphasized the need for more efficient methods of pasture utilization. This has been achieved to some extent by an increase in sheep stocking rates. However, the benefits from high stocking rates are far greater when used for the production of wool from dry sheep than when applied to breeding flocks producing prime lambs. Results from many experiments with wethers (Arnold & McManus, 1960; Drake & Elliott, 1963; Bishop, Birrell & Tew 1966; Morley & Ward, 1966) indicate that as stocking rate is increased total wool production per acre increases substantially. The relationship between total wool production and stocking rate is curvilinear (Bishop et al., 1966) and although the stocking rate which results in the maximum production per acre is higher than that which achieves the greatest economic return (Lloyd, 1966),a considerable increase in farm income can be obtained when the stocking rate of wethers is raised above conventional levels (Chisholm, 1965). The improvement in pasture utilization when wethers are grazed at high stocking rates is brought about by an increase in competition between individual sheep and the consumption of much of the poorer quality and damaged pasture which is otherwise rejected. Increasing competition eventually results in a reduction in feed intake with a concomitant lowering of production. However, the adverse effects of a reduced intake are less for wool growth than for most other forms of production. For example, the results of Bishop et al. (1966) indicate that wool growth of Corriedale - Polwarth cross wethers will continue at a rate of approximately 14 g/day inspite of the fact that feed intake was insufficient to produce a gain in live-weight. A reduction in feed intake has more serious repercussions in a breeding flock. A nutritional stress on the ewe can lead to (a) low live-weight at mating with its effect on ovulation (Edy, 1968) and lambing percentage (Coop, 1962) , (b) small live-weight gains during gestation with low birth weights of lambs from multiple births (Wallace, 1948) and high perinatal mortality (Alexander, 1962), (c) poor lactation and reduced lamb growth rates (Wallace, 1948). The presence of lambs accentuate the decline in food availability and as a result of the low intake of both milk and pasture the lambs grow poorly. Arnold and Bush (1962) found that meat production from a prime lamb flock did not increase when stocking rates were raised from 4 to 7 ewes per acre. In a more recent study (G.W. Arnold, A Axelsen & M.E. Bourke, 1965 - personal communication) it was found that as the ewes were increased from 5 to 7 per acre the number of lambs reared remained constant at 6.2 per acre, but the meat production declined. Many prime lamb producers in southern Australia have attempted to increase stocking rates, but, poor growth of lambs has generally resulted in a large percentage of them remaining unfattened at the end of the period of pasture growth. These lambs are often carried through to the following autumn and further reduce the feed available in the winter. The poor response in meat production associated with increased stocking rates was considered to be of sufficient importance for the Reserve Bank of Australia to provide finance to investigate "the problems of high stocking rates in the prime lamb industry". It seemed logical that the production of meat may be improved if the competition between the ewes and lambs could be reduced. The most common methods by which this is done is to either creep graze or early wean the lambs, thereby giving them access to more pasture of high quality. The results of several studies in England (Spedding & Large, 1959; Dickson, 1959) and Tasmania (Jefferies, Dreaver & Wilson, 1961) suggest that creep grazing systems do produce faster growth rates in lambs when stocking rates are high. However, limited evidence from the Australian mainland (Arnold & Bush, 1962; Fletcher & Geytenbeek, 1968) indicates that the creep feeding of pasture is not advantageous and that the creep feeding of lucerne produces only slight improvements in growth rates. Lambs weaned at 2 to 3 weeks of age can survive at pasture, but their growth is poor (Spedding, Large & Brown, 1961). Wardrop, Tribe & Coombe (1960) found that lambs weaned at 7 weeks of age could grow as well as unweaned controls, but that their response was sensitive to the quality and quantity of feed. However, the results of Cannon & Bath (1967) indicate that, in conditions typical for southern Australia, stocking rates must be raised above 9.6 lambs per acre before any advantage in meat production can be obtained by weaning lambs at 10 weeks of age. Therefore, it seemed that the early weaning of lambs at pasture would not greatly improve production from prime lamb when high stocking rates were used. Because the response to both early weaning and creep feeding was dependent upon the quality and quantity of the pasture, it was reasoned that these systems may be more successful if the lambs were given concentrate diets formulated to meet their nutrient requirements. However, a survey of the literature revealed that there was a dearth of information on the nutrient requirements of lambs and that many recommendations were contradictory. Because concentrate diets which would satisfy the nutrient requirements of lambs could not be formulated with confidence, the major portion of this thesis has been concerned with determining the protein requirements of young, meat producing lambs.
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ItemThe nutrition of multiple-bearing ewes in late pregnancy( 1989)The nutrition of multiple-bearing ewes in late pregnancy and relationships with lamb survival are reviewed (Chapter 1). The frequent reductions in voluntary intake in late pregnancy, the reliance on maternal reserves and the key role of glucose and protein are highlighted. The sensitivity to nutritional manipulation of traits associated with lamb survival and their variation due to litter size are discussed. The traits include lamb birth weight, lamb vigour, ewe mammary growth and colostrum production, maternal behaviour and gestation length. A hypothesis 'That short-term supplementation of multiple-bearing ewes late in pregnancy will improve responses associated with lamb survival' was developed. Supplementing prolific ewes with lupin grain for the final 10 days of pregnancy has previously significantly increased lamb survival rates (Chapter 2). Experiments were designed to test the hypothesis. Treatments included supplements of different grains, nitrogen or rumen undegradable protein and direct infusions of glucose. Responses measured included production traits associated with lamb survival, glucose, urea and fatty acid production rates, some hormone concentrations, voluntary feed intake and mobilisation of maternal reserves. The variation in responses was compared at various litter sizes. Treatments were selected so that results could be modified and then applied directly to grazing sheep in southern Australia. In the first experiment (Chapter 3) a lupin grain supplement fed to Booroola (prolific) ewes in the final 17 days of pregnancy reduced condition score losses compared to no supplement or an oat grain supplement. -Live weight gains were highest with the lupin supplement and with no supplement. There was a trend for milk production at day two post-partum to be higher with the lupin supplement. Some of the multiple-born lambs died because of low colostrum intake, as indicated by low serum immunoglobulin concentrations. The possible importance of colostrum and initial milk production was demonstrated. Colostrum production and milk production on day one and nine were similar from single and multiple-bearing ewes fed a ration containing 100 g protein/10 MJ metabolizable energy and this ration supplemented with formaldehyde-protected casein or urea (Chapter 4). The ration was fed at 90% of the average estimated requirements of all ewes in the final five weeks of pregnancy. Gestation length was two days shorter with the casein supplemented diet which resulted in twin-born lambs from this diet being about 14% lighter than lambs born to ewes fed the basal ration. Glucose production on day 121 was 32% higher with multiple than single-bearing ewes even though intakes were comparable. Many ewes had low voluntary intakes on the grain/roughage ration and this resulted in large energy deficits. On a roughage/ oat grain ration fed for the final seven weeks of gestation, single and multiple-bearing ewes had consistently low and equivalent intakes (Chapter 5). Nonesterified fatty acid production rates on day 115 and 136 averaged 65 % higher for multiple than single-bearing ewes and rates were similar on both days. Glucose production increased by 32 % between these days and was 17 % greater for multiple than single-bearing ewes. The correlation coefficient of fatty acid and glucose production rates was about 0.7 on both days of measurement. The provision of a large glucose source late in pregnancy may be beneficial to multiple-bearing ewes when their voluntary intake potential seems low. Multiple-bearing ewes were infused at the abomasum from day 119 to 145 of gestation with nil, 106 or 207 g glucose /day (Chapter 6). The glucose was estimated to provide an additional 20 or 40 % energy compared to the basal ration of lucerne chaff. The ewes which were infused with glucose gained more weight during the treatment period (90, 159 and 267 g/d for basal, +20% and +40% energy respectively). Litter weight, colostrum yield and early milk production were insensitive to additional energy, as glucose, in the last 30 days of pregnancy in the circumstances where ewes were in low condition and fed a restricted roughage ration containing a high percentage of protein. The insensitivity seemed to lie with increased insulin levels leading to peripheral tissue accretion. Again high variation occurred in colostrum yields, although amounts were higher than in previous experiments. There were significant positive correlations between litter weight and both progesterone and plasma ovine placental lactogen levels in late pregnancy. Colostrum production was negatively correlated to progesterone concentrations measured in late pregnancy. Intake declined close to parturition even with the glucose infused ewes. When ewes were fed a medium quality roughage ad libitum, a lupin supplement in the final 10 days of pregnancy increased colostrum yield by 37% and milk production on day 1 by 28% when averaged over all ewes (Chapter 9). The largest response occurred with the triplet-bearing ewes, which had much lower production than single and twin-bearing ewes. Lambs born to lupin supplemented ewes had faster growth rates to day 1 and 3 post-partum. Benefits occurred either through additional substrates and /or by changing hormonal status, specifically progesterone. Colostrum levels at birth and total milk production to 24 hours were significantly improved when multiple-bearing ewes were supplied with supplements of glucose, lupin grain or undegradable rumen protein in the final 10 days of pregnancy. The basal ration was a medium quality roughage fed at a restricted level. The results provided strong evidence that additional protein which escapes rumen degradation will increase colostrum production near birth and advance the timing of copious milk production. The colostrum and milk yields were negatively correlated to progesterone concentrations near parturition. Prolactin and ovine placental lactogen concentrations measured before and after parturition were poorly correlated with the lactation results. Triplet bearing ewes had lower milk production than twin bearing ewes. There were no effects of the treatments on birth weight, but large effects on ewe live weight change and gestation length. The mechanisms could be due to extra fat mobilisation in late pregnancy with additional protein supplies, changes in hormone status, or possibly the supply of extra amino acids compared to the non-protein treatments. Variability in the colostrum and milk responses on the glucose treatment made it unclear what the role of glucose was for colostrum production. Milk production of multiple-bearing ewes is likely to be below that required by their litter in a cold and wet environment in the first 24 hours when the ewes are fed a medium quality roughage diet (Chapters 7 and 10). Lambs had a potential colostrum intake in the first two hours of an average 110 g and 230 g/kg birth weight during the first day (Chapter 8). This amount was usually above that available to all lambs in the litter from the dam. The potential intake was also above that required in most environments. Limited variation in intake between lambs within a litter may be crucial to survival of the complete litter. It is proposed that protein has a specific effect on the endocrinology of the ewe in late pregnancy. Thus a possible hypothesis consistent with these data is that increased amino acid supply at the tissue level results in a faster clearance of progesterone allowing lactogenic hormones and hormones involved with the initiation of parturition to act. These experiments have thus demonstrated that short-term supplementation of ewes can influence some traits associated with lamb survival, including colostrum production at birth and milk production during the following 24 hours. Multiplebearing ewes will often have lower amounts of colostrum and early milk production than single bearing ewes. Supplementing ewes on medium quality protein/energy pastures with feed sources which provide a high protein yield at the small intestine should increase the initial lactation output and possibly survival rates of multiple-born lambs.
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ItemThe degradation of chloroplast galactolipids during leaf senescence in wheat (Triticum aestivum L.)( 1987)Acyl hydrolase activities were investigated in the primary leaves of wheat (Triticum aestivum L., cv. Egret). Preparations from both mature leaves and leaves induced to senesce in darkness were tested for their ability to hydrolyse the endogenous acyl lipids in wheat leaf thylakoid membranes. The liberation of fatty acids was measured using a sensitive high performance liquid chromatagraphic technique. A lipolytic activity was found to be associated with the thylakoid membranes in mature, non-senescent wheat leaves, which partially hydrolysed the major class of lipid in the thyiakoids, monogalactosyl diacylglycerol (MGDG), producing a lysolipid and free linolenic acid (LIA). The enzyme became active when isolated chloroplasts were incubated at pH 6.0-6.2. Up to half the MGDG present in the membranes may be degraded by this enzyme within one minute from the start of the assay. However, the activity was rapidly terminated under the conditions of the assay. The 'galactolipase' was inhibited by phenylmercuric acetate and p-chloromercuti-benzoic acid, and was inactivated by preincubation temperatures greater than 35C, mild detergents and sonication. Calmodulin antagonists were inhibitory to 'galactolipase', but modulation of the enzyme activity by calcium could not be demonstrated. Effects of galactolipid hydrolysis by the endogenous 'galactolipase' on the physiology and ultrastructure of thylakoid membranes were examined. Incubation of chloroplasts at pH 6.0 rapidly inhibited electron transport activity particularly through photosystem II, and caused uncoupling of ATP synthesis. However,'these effects were attributable to the accummulation of free fatty acids in the membranes, and in the presence of bovine serum albumin (BSA), which sequesters fatty acids from the membranes, no inhibition was observed. Ultrastructural studies revealed preferential degeneration of stromal lamellae and extensive swelling of granal stacks following gaIactolipid hydrolysis, resulting in thylakoid structures similar in appearance to those reported in senescing leaves. This effect was only partly prevented by BSA. In contrast, exogenous LIA caused unsticking of the membranes, but had no effect in the presence of BSA. 'Galactolipase' was able to activate a thylakoid associated, LNA-dependent oxidative chlorophyll-bleaching activity (CHLOX) which has been proposed as a likely mechanism for chlorophyll catabolism in viva. LIA released by galactolipase was four times as effective as exogenous LIA in activating CHLOX. Galactolipase activity in chloroplast preparations declined with leaf age after maturity, reaching a negligible level when only half the MGDG in the tissue was lost. Galactolipase activity was also found to be present in a non-yellowing mutant of Festuca pratensis , whose ability to degrade thylakoid acyl lipids during leaf senescence is impaired. Therefore, no direct evidence was obtained linking the thylakoid-associated galactolipase activity with gaIactoIipid degradation during leaf senescence. However, an alternative role for the enzyme in lipid turnover in non-senescent tissue was discounted, as no turnover of galactolipids could be detected in wheat primary leaves. It is thought likely that the enzyme participates in thylakoid degradation during senescence, but an understanding of its mode of activation in vivo may be required to verify this role.