School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemNo Preview AvailableA study of pathological and ecological factors causing root-rot of subterranean clover (T.subterraneum L.)(University of Melbourne, 1975)The studies reported in this thesis were conducted by the writer at the School of Agriculture and Forestry University of Melbourne, during a two-year period of study leave from the Victorian Department of Agriculture, within the years 1972-1973. This work extends and consolidates research which was commenced almost simultaneously and independently at both the School of Agriculture and Forestry and the Victorian Plant Research Institute, Department of Agriculture in 1970, to investigate a serious root rot disease of subterranean clover in Victoria.
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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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ItemEpidemiological and physiological studies of the effects of peach rosette and decline disease on the peach, prunus persicae L. Batsch( 1975)The incidence in the field of the disease peach rosette and decline (PRD), which is of considerable economic importance in the Goulburn Valley, causing fruit loss and tree death, was shown to increase from 0.9 to 91.3% in an orchard of cv. Golden Queen in 10 years. Similar results were found with the cv. Pullars Cling, in which infection increased from 1.5 to 29.7% over five years. The pattern of spread was mainly from infected trees to contiguous uninfected trees. This is consistent with the view that the main causal agent, prune dwarf virus (PDV), is transmitted only via the transfer of infected pollen : a previous finding in cherries which was confirmed in peaches. Prunus necrotic ringspot virus (PNRV) is the other virus always present in the field in PRD-infected trees. The mode of spread of PNRV is also by pollen. Within the tree, PDV moved erratically from the first infected limb, via phloem but not xylem, into the other limbs well in advance of the appearance of symptoms. Three months after flowering, PDV was detected in 65% of main limbs adjacent to the first infected limbs but in only 30% of limbs more remotely positioned on the tree. However, removing infected limbs within four weeks of flowering, when the initial infection was presumed to have occurred, did not prevent the movement of PDV into the rest of the tree. Laterals from peach trees infected with PRD were tested for the presence of PDV, using woody virus indicators (cvs Golden Queen, Italian Prune and Elberta seedling). Golden Queen was found to be a more reliable indicator for detecting PDV than Italian prune, as the presence of PNRV with PDV killed 71% of the Italian prune buds compared to only 34% of the Golden Queen buds. Golden Queen also developed more obvious foliage symptoms of PDV infection than Elberta seedlings. The probability of failing to detect PDV in infected field trees, using all three indicator plants, was higher in the first year of infection. The rate of spread of PRD was reduced in the orchard by preventing infected trees from flowering, either by removing obviously infected trees or by deblossoming. Removing infected trees resulted in a three-fold reduction in the spread of the disease in two seasons. Removing the flowers from infected trees before pollination reduced the spread of the disease by about half. This, only partial, control of the spread of PRD by tree removal or deblossoming was attributed to the presence of up to 14.3% of trees without symptoms being latently infected with PDV. It was observed that deliberate infection with PDV by pollen also resulted in a slow expression of the symptoms of PRD. The effects of PRD on the growth of young peach trees was obvious in the first three months of growth. There were considerable varietal differences in the severity of this effect. Those varieties based on cvs. Golden Queen or Levis Cling were more severely affected than the variety Elberta. The results from shoot elongation measurements agreed with those obtained from conventional growth analysis methods. These latter experiments showed that, after three months, the dry weight and leaf area of infected Golden Queen plants were reduced by 94%. The fruit yield from mature PRD-free trees was three times that of trees infected for the first season, even though symptoms were apparent only on one limb; and six times that from chronically affected trees infected for two seasons. The effect of virus infection on the photosynthetic ability of single, attached peach leaves was studied under laboratory conditions using infra red gas analysis. The constants derived from the equations describing the relationship between net photosynthesis (Pn) and both irradiance and CO2 concentration were used to analyse the effects of infection by PRD on photosynthetic characteristics of the leaf. The asymptotic value of Pn (Pmax) in young leaves was reduced 15% by PRD-infection, mainly through an increase in the "residual resistance" to 002 diffusion and a decrease of 23% in the parameter indicating photochemical efficiency. There was also evidence that the gas phase resistance was higher in infected leaves at low levels of irradiance. Dark respiration was 51% higher in infected leaves, but this difference was not significant. PRD did not reduce Pn in 60-day-old leaves, normal leaf senescence having a predominant and greater effect. It was concluded that PRD infection had its large effects on growth via a reduction in leaf area; the effects on the photosynthetic capacity per unit leaf area being minor. An effect of PRD infection on the translocation of 14C-assimilatesout of leaves was also observed. Infected leaves retained twice the assimilates than did uninfected leaves. It is concluded that the most promising methods of control of PRD include removal of infected trees, deblossoming suspected infected trees until diagnosis is confirmed, use of virus-tested plants, the gradual destruction of infected orchards and protecting young, healthy orchards from infection either by barrier crops or deblossoming the young plants until they reach an economic bearing age.
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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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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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