School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemA study of the effects of high stocking rates on the production of perennial pasture and its utilization by dairy cattle( 1973)The work in this thesis consists of a study of the effects of increasing the stocking rate from 2.2 to 3.2 cows per hectare on the production of dairy cattle and perennial pastures from 1966-70. (a) Milk production per cow was significantly reduced (P < 0.05) by the increase in.:stocking rate with the exception of the first year. (b) The yield of milk and milk components per hectare was increased (P< 0.05) by the increase in stocking rate except for 1968-69 when a drought occurred and the increases were not large enough in most components to attain significance (P)00.05). The yield of nitrogen in milk per hectare was significantly increased (p<0.05) in all years with stocking rate. (c) There was a tendency for the high stocking rate to lower the percentage of all components in milk with the exception of nitrogen which remained unaltered. However significant differences were not recorded consistently in any one component over the four lactations studied. (d) No significant differences (p>0.05) in seasonal or annual net pasture production were recorded between stocking rates. (e) The increase in stocking rate caused significant increases (1).<0.01) in grazing pressure, reductions in pasture availability (P<0.01) and higher contents of crude protein (1).<0.01) in pasture excepting spring and on two occasions in winter. (f) Estimates of feed intake at the higher stocking rate showed a significant increase in pasture harvested (P < 0.01) per unit area every year. However with the exception of the first year feed intake per cow was significantly reduced (P<0.01). (g) The ratio of pasture consumed per hectare to milk production per hectare was not significantly affected (P>0.05) by the increase in stocking rate.
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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 on metabolizable energy values of poultry feedstuffs( 1974)This thesis describes studies carried out on metabolizable energy values of a number of feedstuffs available in the State of Victoria for poultry nutrition. These investigations were part of a research project in the poultry research section of S.S.Cameron Laboratory (Animal Research), Werribee. I was responsible for the design and execution of the experiments and for all chemical analyses. The statistical analysis was done by Mr. Jardine, Biometrician, Department of Agriculture, Melbourne. The interpretation of the results and the preparation of the review and the manuscript have been my responsibility. Chapter 1 includes a literature review of the different methods that are used in determining metabolizable energy values for poultry as well as the factors that may affect the metabolizable energy content of diets and feed ingredients. Chapter 2 describes the general procedure of the metabolizable energy assay. The specific material and methods of the experiments were included in each of the experimental chapters. Chapter 3 outlines the balance studies carried out to determine metabolizable energy values of various feedstuffs with different sexes. A comparison between the biologically determined values and those calculated from the chemical composition of the feedstuffs also was included. Chapters 4, 5 and 6 concern the investigations carried out to study the effect of sex of chicks on metabolizable energy content of soyabean, rapeseed, fish meals, tallow and sunflower oil at various levels of inclusion in diets. Chapter 7 summarises the results obtained and recommended avenues for future work. Note: The experimental chapters (3-6) are presented in the format required for publication in the Australian Journal of Experimental Agriculture and Animal Husbandry.
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ItemThe utilization of livestock wastes by ruminants( 1975)In studies with sheep faeces it was found that the longer the faeces were stored,the lower the content of moisture, crude protein and ether extract and the higher the content of nitrogen free extract. Crude fibre and ash contents were relatively constant. The in vitro technique and the in vivo nylon bag technique to estimate dry matter digestibility (DMD) and organic matter digestibility (OMD) of excreta were investigated. Using an oven as an incubator in the in vitro technique, DMD and OMD coefficients of the faeces of sheep, cattle, pig and the manure of poultry were 19.2, 18.9, 45.7 and 62.6,and 10.9, 8.6, 28.2 and 30.7, respectively. Using a waterbath as an incubator DMD and OMD coefficients were 18.8, 16.8, 31.3 and 53.7,and 17. 0, 14.6, 28.0 and 48.2, respectively. The different techniques are discussed. The in vivo nylon bag technique using nylon "A" in sheep and using nylon "A" and "B" in cattle was carried out for 24, 48, 72 and 96 hours incubation periods. DMD and ODM coefficients are recorded, and the procedures are described. The effects of continuous feeding for 70 days of dried pig faeces, supplemented in the diet of 21 sheep were studied. Seven dietary treatments were imposed. Diet A was a pelleted medium quality hay containing 10.3 mg Cu/kg DM and 0.2 mg Mo/kg DM. Diets B,C and D contained 15% pig faeces which gave a dietary Cu concentration of 101.3 mg/kg; molybdenum was added to diet C to give a concentration of 90 mg/kg DM and to diet D to give a concentration of 175.5 mg/kg DM. Diets E, F and G contained 30% pig faeces (192.5 mg Cu/kg DM) ; molybdenum was added to diet F to give a concentration of 90 mg/kg DM, and to diet G to give a concentration of 175.5 mg/kg DM. Sulphate was added to all diets at the rate of 1.08% of the dry matter. During the experiment all animals survived. Inclusion of dried pig faeces in the diets reduced the digestibility compared with the control diet. The maximum plasma GOT activity detected was 182 units/ml reading at 505 nm wavelength. Blood Cu concentrations ranged from 0.28 ug/ml to 3.50 ug/ml. Wool Cu concentration ranged from 2 to 8 mg/kg DM. Kidney Cu concentration ranged from 19.2 to 190 mg/kg DM. Over the 70 days of the experiment, the Cu retention for groups A - G were, respectively, 210 + 17, 680 + 149, 1191 + 39, 1054 + 20, 53 + 185, 1079 + 164 and 1225 + 157 mg. Liver Cu concentrations were, respectively, 718 + 174, 1186 + 176, 1440 + 248, 1522 + 477, 1740 + 212, 1560 + 46 and 1703 + 384 mg/kg DM. There was no correlation between total Cu intake and Cu retention in the body. However, there was a relationship between total Cu intake and liver Cu concentration ( r = 0.827 ) and between total Cu intake and faecal Cu concentration ( r = 0.997 ). Almost all of Cu output was excreted as a faecal Cu. Histopathological examination showed variable liver damage with some sheep showing single cell necrosis , particularly in the livers of sheep receiving 30% dried pig faeces in the diets. No kidney abnormalities were found. It was concluded that pig faeces, with no processing other than drying, are poorly utilized in the diet of sheep and with continuous feeding may induce copper toxicity.
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ItemSupplementary feeding of slow growing lambs( 1976)Mount Derrimut Field Station, approximately 320 ha, is situated 22.4 kilometers to the west of the Melbourne General Post' Office. It is operated by the Faculty of Agriculture and Forestry of the University of Melbourne, primarily for undergraduate teaching in Agricultural Science but also as a Centre for research. The climate is of a Mediterranean type with an average annual rainfall of 450 min., mainly of winter incidence. Typically the growing season begins about mid August and finishes in late November to early December. Soils are of volcanic origin and are mildly leached, ranging from shallow stoney red loams on the slopes to. moderately deep grey clays on the flats. The pastures are generally of improved types although there are some native species particularly in those paddocks with large areas of rocky outcrops. The 290 ha, of land available for cropping and grazing carry a herd of thirty crossbred beef cows plus about fifty followers of various ages and a flock of 500 Corriedale breeding ewes. Each year about 60 ha, are sown to wheat, barley and oats. Selection in the sheep flock has primarily been directed towards the genetic improvement of wool quality and lambing percentages: less attention has been paid to the improvement of the lamb growth rates. Over the past ten years considerable difficulty has been experienced in growing the lambs to prime condition, suitable for slaughter, by the time the pastures have matured towards the end of the spring growing season. The ewes were mated during early March so that they would lamb in August when the spring flush was occurring. The lambs then had about three months in which to grow to slaughter weight before the pastures matured. In recent years, mating has been changed to mid January, so that lambing would occur during June and. July. It was anticipated that this early mating, although possibly having an adverse effect on lambing percentages, would' allow the lambs a further four weeks of growth before pasture maturity. The strategy of early mating has in part improved the numbers of lambs in prime condition at the end of the season but there is still a variable number of lambs that are not in prime condition at the normal sale time. These lambs must either be carried over into the dry summer and sold in the following autumn, or sold at the normal time as store lambs at a considerably lower price. In 1973 investigations were started in an attempt to develop management strategies that would reduce or eliminate the number of Underweight lambs by the time of pasture maturity. Preliminary studies in which all lambs in the Mt. Derrimut flock were weighed at birth and at subsequent six week intervals, suggested that lambs that were lightweight at pasture maturity were also lightweight at six weeks of age. The correlation coefficient between six. week weight and the subsequent length of time required to reach slaughter weight was found to be -0.60. Although the lightweight lambs had lower birth weights than the lambs achieving slaughter weight at the normal. time, most of the advantage in weight of normal lambs was made during the first six weeks of life. Wardrop (1968) also found that in a prime lamb producing flock under southern Australian conditions, the correlation coefficient between liveweight at eight and seventeen weeks of age was 0.91. It was concluded that: (a) lambs that were lightweight at the normal sale time could be identified with reasonable confidence at about six weeks of age, and that (b) preferential treatment in the form of a concentrate diet offered sometime between six weeks of age and normal slaughter time, may reduce or eliminate the number of lambs carried-over beyond the end of the growing season. This thesis presents the results of studies designed to test these hypotheses.
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ItemEffect of body condition at calving on milk yield of the dairy cow( 1978)The experiments reported in this thesis were done at the Dairy Research Institute (Ellinbank), Department of Agriculture, Victoria. This Institute is situated 100 kilometres east of Melbourne in the West Gippsland Region. The information currently available on the effect of precalving feeding on subsequent milk yield of grazing dairy cows is limited and largely of a qualitative nature. This thesis attempts to provide quantitative information on which feed management decisions can be made in the precalving period with some degree of confidence. The design, analysis and interpretation of the two experiments reported in this thesis were done primarily by myself. I was also actively involved in development of the condition scoring system reported in this thesis and in collecting, analyzing and interpreting data in order to provide an objective description of the condition scoring system. Chapter 1 reviews the literature on precalving feeding of the dairy cow indicating the apparent conflict in the results of different experiments which cannot be explained because of the confounded design and inadequate reporting of the results of experiments. Gaps in our current knowledge of precalvins feeding are also highlighted. Chapter 2 reports on an experiment which was done as part of a series of three experiments at Ellinbank to determine the relative importance of precalving liveweight change and body condition at calving on milk yield of dairy cows. These three experiments have been written up and accepted for publication in the Australian Journal of Experimental Agriculture and Animal Husbandry. Chapter 3 describes a system for scoring the body condition of dairy cows which was developed at Ellinhank with the assistance of the author. Chapter 4 reports on an experiment which quantifies the effect of body condition score at calving on milk yield under two levels of feeding after calving. This experiment and a more recently completed experiment with stall- fed cattle in different condition scores are to be combined and submitted shortly to the Australian Journal of Experimental Agriculture and Animal Husbandry. In Chapter 5 the experimental results are discussed in the light of continuing work and the industry significance of the work is emphasized.