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.