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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ItemBeef-cattle production in the Western District of Victoria : technical and economic relationships between beef cattle and sheep( 1965)Sheep-and-wool production and beef-cattle production are combined on many grazing properties in the Western District of Victoria. In the past beef cattle have generally been regarded as less profitable than sheep as a sole enterprise on a per-acre basis. In previous surveys it has been found that graziers believe that sheep and beef-cattle complement one another in a variety of circumstances because of the different effects of the two types of animal on pasture. It has also been found that sheep and beef cattle on grazing properties are frequently supplementary with respect to labour. The thesis has two main objectives. First it investigates whether the currently available analytical models based on static economic theory are adequate to solve problems of resource allocation between sheep and beef cattle grazing the same pasture. Second, it investigates whether many graziers carry beef cattle partly or solely to satisfy goals other than profit maximisation. The method of achieving the first objective was to compare the static economic theory relating to enterprise combination, and published work dealing with the problem of selecting the optimum combination of two enterprises, with the real situation existing on grazing properties carrying both sheep and beef cattle. The second objective was investigated by means or an interview survey of graziers running both sheep and beef cattle in six Western District parishes. A considerable amount of technical information about beef-cattle production in the Western District was collected in the course of the survey, and the more important points are summarised in the thesis. Of particular interest are the findings that very few graziers purchased cattle for fattening purposes, and that beef cattle were relatively more important on large properties than on small properties. It was concluded that static economic theory does not provide an adequate basis for the description of the situation where sheep and cattle graze the same pasture, or for the determination of the optimum allocation of resources between sheep arid beef cattle grazing together. Sheep and cattle graze pasture differently, and therefore different pastures result as the sheep-cattle ratio is altered. In this situation, the postulates on which the iso-resource function is based, that the shared input or inputs should remain homogeneous and constant in quantity as the outputs of the products change, are violated. Thus strictly speaking it is not possible to derive a valid iso-resource function relating the sheep and beef-cattle enterprises with respect to pasture when the sheep and the cattle graze the same pasture. However, if the changes in the pasture are disregarded, it is possible to design experiments to produce practical approximations of iso-resource curves relating sheep and beef cattle. Information obtained from graziers in this and other surveys, and the results of experiments, strongly suggest that for practical purposes it is reasonable to think of an iso-resource curve for sheep and cattle with respect to pasture as being concave towards the origin, that is, the sacrifice rate of sheep for cattle increases as more cattle are added on a sheep property. Farmer estimates and experimental evidence suggests that the marginal sacrifice rate on most properties may be lower than is generally assumed (nutritional standards imply a linear rate of eight merino whethers per 1,000 lb. steer). Almost all the survey graziers believed that the overall relationship between their sheep and their beef cattle with respect to their total feed supply over the whole year was a competitive one. Most estimated that their sheep and their cattle were complementary or supplementary with respect to pasture over a part of the year, including the Spring, and that their sheep and their cattle competed for scarce pasture at some time in the autumn and winter. The survey results showed that the most important reason for the presence of beef cattle on the survey properties was the value of cattle in controlling and utilising pasture and weed growth. However the value 0f cattle for that purpose appeared to decline as the sheep stocking rate increased. It appeared that on many properties the importance of beef cattle in pasture control was a consequence of a desire on the part of the grazier to maximise profits within the restrictions imposed by limitations on sheep numbers including the grazier's desire to limit his personal effort. Beef cattle were also frequently carried for the reason that they provided a means of stabilising income from year to year. Although the survey results tended to confirm previous findings that sheep and beef cattle are supplementary with respect to labour at certain times during the year, and that beef cattle generally require less labour per unit of return than sheep, few graziers said that they carried beef cattle for those reasons. It was concluded that substantial minority of the survey graziers did carry beef cattle partly or solely to satisfy goals other than profit maximisation. The most important of these goals was the minimisation of personal effort, which was shown not by giving labour as a reason for carrying beef cattle, but indirectly in the affirmation of the value of cattle (rather than additional sheep) in pasture control. A few graziers were motivated by a personal preference for beef cattle. In the situation where the available economic theory is inadequate to solve problems of resource allocation between sheep and beef cattle, and where a substantial proportion of graziers carry beef cattle partly or solely for reasons other than profit maximisation, there is little scope for sophisticated economic procedures. Given additional experimental data to provide indicators of probable "substitution rates", it seems that the allocation of resources between sheep and beef cattle on properties such as those in the survey can best be improved by budgeting possible adjustments.
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ItemBody composition studies in the sheep( 1957)When he was Senior Lecturer in Animal Physiology and Production at Melbourne University, Dra T.J. Robinson initiated a series of experiments concerned with the body composition of fat lambs. This study was carried out by the following team of workers under Dr. Robinson's leadership: Mr. Blair-Weste Physiology School; Dr. Binet, Statistics Department; and myself from the school of Agriculture. The aims of this study were to determine: (1) Whether the quality and conformation of a fat lamb carcass could be defined by external body and probe measurements. (2) Whether the antipyrene technique could be used to estimate the total body water in lambs and hence their body composition in terms of total waters fat, and fat free tissue. (3) What relationships might exist between the specific gravity of a lamb carcass and its fat content. (4) Whether sample joints in a lamb carcass were representative of the whole carcass in terms of total bone, muscle, and fate and therefore of total water, fat, and fat free tissue. The first part of the investigation was carried out by Drs. Robinson and ninety and I was in no way involved. The other experiments were carried out jointly by Dr. Robinson, Blair-West and myself. In October, 1953, Dr. Robinson divided 8 newly-born Suffolk cross lambs (all singles) into four similar pairs, and fed each pair on a different plane of nutrition. The lambs, which were made to grow along predetermined growth curves, were weighed fortnightly and antipyrene determinations were carried out monthly. Thus the growth curve of each lamb could be drawn and split up into its component parts - i.e. H2O, fat and fat-free tissue. All lambs were killed when they reached 80 lbs. live weight, and the carcasses deep frozen. When I joined the team, in January, 1955, the carcasses were removed from the cold store and I carried out the specific gravity determinations on them. In order to test the worth of both the antipyrene and specific gravity techniques some standard methods of estimating body composition had to be used as a comparison. It was hoped that the specific gravity of the carcass would give a measure of chemical fat content of the carcass and that antipyrene estimations would give a measure of the total body water in the live sheep. The standard technique used for assessing these estimates was a complete chemical analysis of each lamb into total water, fat protein and residue. One side of each carcass was dissected into total bone, muscle, subcutaneous and intermuscular fat. It was then possible to assess the relationships between the physical and chemical composition of the carcass and the relationships between the physical and chemical composition of sample joints in the carcass and the total carcass. I was responsible for carrying out both the carcass dissections and the chemical analysis. During the course of this work (February, l956), Dr. Robinson took up a new appointment as. Professor of Animal Husbandry at Sydney University. I remained in Melbourne to complete the work under the direction of Dr. D.E. Tribe, the newly appointed Reader in Animal Physiology and Production. The experimental work reported in this thesis is limited to that part of the study for which I was responsible. It will be appreciated therefore, that its full significance lies in its relationship to the work of the other members of the team.
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ItemSome effects of botanical composition of pasture on the liveweight and wool production of sheep( 1972)Until recently, the main evidence on which to base pasture mixture. recommendations in Victoria, has been district experience and the results from dry matter ( "mowing") experiments. The grazing experiments described in this thesis, were initiated by Messrs. R. Twentyman, R. Newman, R. Allen and K. Maher of the Department of Agriculture during the period, 1960-196. Their aim was to develop some objective appreciation of the relative value for animal production of some of the sown and unsown species in Western district pastures. In addition to pasture species evaluation, they sought information on the relationship between pasture growth and animal production. Such information is needed so that Agrostologists can better evaluate the many pasture management factors (such as fertilizers, seeding rates, seed. treatments, herbicides, insecticides and defoliation treatments) that affect pasture growth and for which advice is frequently sought.
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ItemStudies in animal husbandry and agricultural history( 1963)About 8,000 years ago man began domesticating wild animals and turning their growth and production to his own use. Since this time considerable progress has been made towards the complete utilisation of domesticated animal products but only now is the efficiency of production of these products being investigated. To increase this efficiency a thorough understanding of animal body functions is essential. The importance to the ruminant of one body function - salivation, has not been established although various aspects of this subject have been investigated in recent years . To continue these investigations the development of total salivation in . lambs and the effects of the diversion of saliva on the rumen function in adult sheep were examined. In this second experiment the effects of anaesthesia and lateral recumbency on rumen function were also examined because if the use of these unnatural conditions in some experimental techniques. Some animals have been domesticated but many have not. Nearly 8,000 years have passed since the predecessors of our present day domesticated animals were tamed and conditions have changed considerably. Hence it is feasible that domesticated animals may be less efficient producers of the animal products we now need, than the wild animals. This may be particularly true with regard to protein production in the form of lean meat. To investigate this proposition a body composition study was made on a population of wild kangaroos, and an assessment made of this animal species as a potential producer of lean meat. Not only may the efficiency of agricultural production be increased by re-assessing the livestock potential, but this may also be achieved by re-assessing the agricultural use of any given area of land. In countries settled and developed by people from other countries, the new settlers have applied to the new land the agricultural practices of the old. This has often occurred inspite of vast physical differences between the two countries. The practices have been modified and adapted, the crops and livestock acclimatised, nevertheless the whole range of possible forms of agriculture are usually never investigated. In southern Victoria, for almost a century, vines were grown by European settlers had been familiar with these plants in their own countries. The success and failure of the cultivation of this crop by Europeans in a country very different from their own is examined in the second part of this thesis.