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 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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ItemAn evaluation of timber drying problems in terms of permeability and fine structure( 1970)The relationships of difference in rate of drying to permeability and wood structure were determined for two angiosperms and one gymnosperm. These investigations took two particular drying problems as a basis for study and attempted to explain why: - heartwood of Nothofagus fusca (red beech) takes many times longer to dry than sapwood. - green sapwood of Pinus radiata (radiata pine) dries readily but, if dried and pressure-treated with water-borne preservatives, its subsequent drying is greatly retarded. Test material was used from 14 trees of N.fusca from New Zealand, four trees of Eucalyptus regnans (mountain ash) and seven trees of P.radiata from Victoria, Australia and the experimental work was carried out under three headings: (a) Unidirectional drying. Small specimens, sealed on all except one pair of grain faces, were dried in a laboratory kiln at temperatures up to 60C. Comparisons were made between radial and tangential drying in sapwood and heartwood or in green and resaturated specimens; effects of treatments such as steaming were also assessed. Moisture gradients were determined to show the contribution of free water movement to overall drying. (b) Permeability studies. A method was developed to measure the transverse permeability of green wood to the flow of micro-filtered water; established methods were used for longitudinal permeability. Data for P.radiata met the requirements allowing application of Darcy's Law for flow of fluids through inert porous media and N.fusca approximated them. Pathways of flow were determined with chemical stains. (c) Wood structure. The transmission electron microscope was used to compare the appearance of pit membranes and the cell walls in sapwood and heartwood of N.fusca. In P.radiata, emphasis was on determining the percentage of bordered pits that were aspirated in sapwood - green, after drying and resaturation and after various treatments - and relating this to differences in drying and permeability. The main conclusions drawn from this study are: (a) The green sapwood of N.fusca and E.regnans is permeable to micro-filtered water in the radial and tangential directions. After drying and resaturation, the permeability of N.fusca is unchanged but that of E.regnans is drastically reduced, particularly in the tangential direction. The heartwood of both species is impermeable when tested at a pressure differential of 40 cm.Hg. (b) Differences in the permeability of N.fusca can be explained by differences in the appearance of pit membranes in sapwood and heartwood: in heartwood, the membrane surfaces are usually completely occluded when viewed as replicas in a transmission electron microscope; in sapwood, the surfaces are always less occluded often exhibiting a clean primary well texture. It is inferred from studying the effects of various extraction treatments that the pit membrane surfaces in sapwood are less occluded than indicated by the appearance of replicas. (c) Plasmodesmata may provide pathways for mass movement of liquids in the radial direction in the wood, but, in other pits, without obvious pores, permeability probably results from movement through the general structure of the pit membrane. (d) Heartwood of N.fusca takes several times longer to dry than sapwood because of its reduced permeability coupled with lower rates of moisture diffusion. (e) Contrary to previous reports, at least 80 percent of the bordered pits in green sapwood of P.radiata are open, irrespective of distance from the outside of the tree. After drying and resaturation most pits are aspirated and the wood is much less permeable than in the green state. (f) The condition of the bordered pits has an effect on the rate of drying in the tangential direction - causing a marked reduction in resaturated material - but has no appreciable effect on radial drying which is little different in green or resaturated wood.
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ItemThe persistence and productivity of subterranean clover in southern Australia with special reference to rate of development in different cultivars( 1971)Subterranean clover, Trifolium subterraneum L. (commonly referred to as sub clover) has long been recognised as the key to improvement of annual pastures in southern Australia. Although the precise acreage of sub clover is difficult to determine, Donald (1970) has suggested that it may have been sown on as much as 80% of the present estimated area of 50 million acres (20 million ha) 0f sown pasture in this region (see Fig.1). This area (especially the western part of it) has a Mediterranean-type climate with mild wet winters and hot, dry summers. The total annual rainfall varies from about 8 inches (200 mm) to 40 inches (1000 mm) and the length of the growing season (the period during which rainfall relative to evaporation is sufficient to support plant growth) ranges from less than 4 months in the low rainfall areas of Western Australia to 10-11 months in some parts of south-eastern Australia. The species of which the pastures in this area are composed, are predominantly annuals. They become re-established each year following the autumn break, and flower and set seed during the spring prior to over-summering in the seed phase. The autumn break is on average later and the onset of the dry summer period earlier as the annual rainfall becomes smaller, but, in any one location, the year to year variation in the length of the growing period is considerable. In isolated areas reasonable constancy in length of growing period is achieved by autumn and spring irrigation. Pastures may be permanent, becoming re-established each year over an indefinite period, or temporary, in which case a pasture phase of one to several years alternates with a cropping phase, mainly cereals, of 1-3 years. Sub clover has proved to be well adapted to the conditions prevailing in southern Australia and it has played a key role in the pastures because of its capacity to fix atmosphere nitrogen. This together with liberal dressings of superphosphate which have been the rule has greatly improved the fertility status of the soils, thereby increasing the productivity of the pastures themselves and the crops grown in sequence with them. That sub clover had agricultural potential was first realised by Mr A. W. Howard in 1889 in the Mt. Barker district of South Australia, and his efforts to publicise it in the face of public indifference, have been well documented (Hill 1936; Davies 1951; Morley 1961; Symon 1961). There was a period of little progress. Then, through the efforts of many research workers, came an advance in knowledge of the plant and how it could best be used, and, with this, a tremendous increase in its use. There still exists opportunities for its greater use in new areas in southern Australia and for better use in some existing areas. This will require additional research to provide new cultivars and a better understanding of the interaction between genotype and environment. Matching of the genotype with the environment and the importance of this in determining the persistence and productivity of the species will be the main theme of this thesis. The thesis begins with a literature review in which variation within the species and how this is implicated in its widespread use in agriculture are the underlying considerations. This is followed by a report of work concerning the effects of various factors of the environment on the developmental physiology of the plant.
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