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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ItemGrowth, body composition and related studies of farm animals( 1975)The publications included in this thesis report experiments done while the candidate has been a member of staff at the University of Melbourne (1957-1975) . The thesis is divided in five sections, as follows:- (Paper Nos.) Growth and development of farm animals 1-20. Physical studies of the alimentary tract of dairy cattle 21-24. Investigations of the skin of cattle 25-27. Animal behaviour 28-29. Miscellaneous papers on animal production 30-33. The section entitled "Growth and Development of Farm Animals" begins with a review (Paper No. 1) of the results of some of the papers in this section. It is followed by two papers (2, 3) which re-analyse the data of other authors and present hypotheses which are later developed and tested (in papers 4 to 20) . Papers numbered 4, 7, 25, 26, 27, 28, 29 were presented as part of the candidate's Ph.D. thesis. They are included, not for examination, but because they are related to other work in this thesis. Papers numbered 2, 3, 5 are related to material in the same Ph.D. thesis. In all papers where authorship is shared, the joint authors were either scientific colleagues, research assistants or graduate students. In all cases, the candidate made a contribution in the collection of the data, and was responsible for the design of the experiments. He was also responsible for the supervision of the work and played a major role in preparing it for publication. Where the candidate's name appears either as sole author or as senior author, he was directly responsible for and involved in all aspects of each experiment.
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ItemGrowth rate and body composition of cattle( 1971)A study has been made of the effect on body composition of growing Angus steers at three different rates. On reaching a live weight of 300 kg, animals were allocated to three treatments, viz; (i) a high growth rate (H):- 0.8kg/day (ii) a low growth rate (L):- 0.4kg/day (iii) a high growth rate 0.8kg/day followed by a period during which live weight was maintained constant (HM). The animals in each group were individually penned and the different growth rates were achieved by controlling intakes of a pelleted concentrate feed. Two animals were killed at 300 kg and the remaining 27 animals (nine in each treatment) were killed at common live weights of 330, 363, 400 and 440 kg. Analyses of the data by covariance were made using the logarithmic transformation of the allometric equation y = axb. At the same full body weight (FBW), HM animals had a greater empty body weight (EBW) than L animals, but the differences between H animals and the other groups were not significant. At the same FBW, hot carcass weight (HCW) was greater in the HM group than in both the H and L groups. As a proportion of.EBW, HCW was greater in both the HM and L groups than in the H group, indicating a greater offal component of EBW in the H animals. The loss in weight of the dressed carcass during storage at 2C for 24 hours was similar in all three groups and amounted to 0.98% of HCW. The proportion of HCW in the fore- and hind-quarter was similar in each group. The composite weight of the lungs, trachea, heart and skirt muscle (LTHS) was unaffected by the different growth rates. Liver weight, however, was lower in both the HM and L groups than in the H group. Moreover, the difference in liver weight between the H and L groups increased as liveweight at slaughter increased. Maintenance of live weight in the HM animals caused a reduction in the weight of the kidneys while the low growth rate of L animals was associated with an enhanced growth of the spleen. The weight of the pancreas was similar in the H and L groups while, at the heaviest live weight (440 kg), there was an apparent loss of pancreas tissue during the maintenance period in the HM group. The combined weight of the head, feet and tail (HFT) was greater in the animals from both the HM and L groups than in the H group. This was a reflection of the older age of the HM and L animals at slaughter. Hide weight was similar in both the H and L groups while the weight of the hide in the HM animals showed a differential effect of live weight compared to the H treatment. At the lowest killing weight (330 kg), the hide showed an apparent loss in weight. during the maintenance period while at the highest killing weight (440 kg) it showed an increase in weight. These differences in hide weight may have been related to seasonal effects on cattle coats and on skin thickness.
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ItemAn analysis of the problems of estimating the thyroid hormone level in the blood of domestic animals, and the effects of varying that level on the marketable products of such animals( 1957)In the field of animal husbandry it is becoming increasingly apparent that maximum efficiency of production cannot be attained without careful attention to the health of the animal, and to the balance between the animal and both the internal and external environments. For example, if artificial methods are used to increase production of milk without at the same time increasing, the feed intake the result is generally a decline in the health of the cow which may eventually lead to serious illness. Much recent research in this field has been concerned with the function and activities of specific organs rather than with the body as a whole, showing; that the factors involved in production are much more numerous and varied than was originally thought. Examples of this type of research are the intensive investigations at present being conducted into rumen activity and microflora, wool fibre growth, mammary gland function, reproductive activity and the role of various endocrine glands in production. Of the endocrine glands, apart from those directly concerned in reproduction, the one most studied has been the thyroid which has been shown to play an important part in practically all spheres of animal production so far investigated. It was the aim of this experiment to establish a method for determining thyroid activity which would then allow us to investigate the relationship between this activity and various body processes in the normal animal. In the normally functioning animal the thyroid serves chiefly as a homeostatic mechanism maintaining the body functions at a steady level of activity and, to a certain extent, controlling the response of the body to changes in the external environment. Its effects are more apparent when the thyroid activity is altered in any of the many ways to be considered later. The lowering of the thyroid hormone output produces an animal with typical symptoms - low Basal Metabolic Rate, low body temperature, low reproductive capacity, decreased growth and development in young animals, increased fat deposition, sluggishness, drying and thickening of the skin and falling hair. On the other hand the hyperthyroid animal shows an. increased Basal Metabolic Rate, high body temperature, leanness, restlessness and, in some cases, protruding eyes. These facts have recently been put to practical agricultural use. Raising the thyroid output leads to a significant increase in growth rate, milk yield and egg production. Lowering; the level has proved a successful method of fattening pigs and fowls for meat production. These aspects are dealt with in the review of literature.
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ItemA study of wheat crop physiology in relation to time of sowing, rate of sowing and fertilizer application( 1963)A crop physiological study upon yield in wheat was undertaken at Wagga, located in the wheat belt of southern New South Wales, in 1961 and 1962. The effects of time of sowing, rate of sowing and fertilizer application were investigated. The variety, Heron, was used throughout. Comprehensive measurements during the growth cycle of the crops were made upon total dry weight and its components, photosynthetic area, evapotranspiration, soil moisture stress and plant moisture stress (using the leaf relative turgidity technique). Time of sowing had little effect on the soil moisture available to the crop at flowering. However post flowering climatic conditions were hotter and drier for the later sown crops, and consequently plant moisture stress occurred sooner after flowering. Yields fell in both years with later sowings,at an average rate of 2 bushels/acre for each week' s delay in sowing. Increased fertilizer application and increased rate of sowing increased the vegetative growth, and the potential yield at flowering, but this was associated with small reductions in the soil moisture at flowering and an earlier onset of plant moisture stress. The increased vegetative growth usually resulted in increased grain yields, but under drier conditions grain yields were reduced. Nitrogenous fertilizer appeared to have additional effects on the crop which may under some conditions be detrimental to grain yield. Certain interrelationships within the soil/crop system were evident from these trials. Evapotranspiration increased as photosynthetic area index increased when soil moisture was adequate. Leaf relative turgidity at sunrise was closely related to soil moisture stress. Grain yield variation was highly correlated with variation in photosynthetic area duration after flowering. Photosynthetic area duration was related to photosynthetic area index at flowering and to the level of plant moisture stress after flowering, which governed the rate of senescence of this photosynthetic tissue. These results and the value of this type of crop physiological study of yield in wheat are discussed. The application of some aspects of the results to wheat agronomy and breeding is apparent.
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ItemExperiments in animal husbandry( 1961)
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