School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemThe physical and functional development of the forestomachs of the lamb( 1960)In this thesis a study of the physical and functional development of the forestomachs of the lamb is presented. The experimental work can be divided into three main fields as follows:- a) Studies on the physical development of the fore- stomachs. b) Studies on the functional development of the reticule-rumen. a) Field work in which the above studies have some direct bearing. The main findings of these studies have a) PhysicaI development of the forestomachs: In grazing lefts the four stomachs have reached their adult proportions by approximately 8 weeks of age. The type of diet can markedly influence the rate of growth of the forestomachs, and in general, it would appear that plant food is needed for the normal development of the forestomachs, and It plant food is excluded from the diet the development of the forestomachs is retarded at about the level found in the 3 week old grazing lamb. The main changes in the histology of the forestomach walls takes place during the last third of foetal life, and the adult his histological features are all present at birth. The major post-natal histological changes are complete by 56 days of age. It would appear that age is the main factor controlling the histological development of the forestomachs, and that plant material is necessary for the full development It of these organs. It was also shown that different diets can cause differences in the appearance of the rumen mucosal surface, stratum granulosum and stratum corneum. b) Funcational development of the reticulo-rumen: It was postulated that the functional development of the reticulo-rumen of the grazing iamb could be divided into three phases - a non ruminant phase (0 - 3 weeks of age), a transition phase (3 - 8 weeks of age) and an adult ruminant phase (8 weeks of age onwards). If plant food was excluded from the diet, the lamb remained in the non- ruminant phase, however, once plant food was fed to these lambs the reticule-rumen function reached the adult levels within one week. c) Field studies: As the forestomachs of the grazing are qualitatively and quantitatively fully developed by approximately 8 weeks of age, it is possible to ween lambs of this age with no check to their growth rate, provided the pastures are relatively high in protein and are not at the late flowering or seeding stages. The milk yield of the grazing ewe measured by the oxytocin technique gave consistently higher recordings throughout Iactation than the conventional lamb suckling technique. By the tenth week of the lactation the milk yield, as measured by both techniques, had fallen by half. There was a high correlation between the milk yield of the ewe and the lamb live weight growth up to seven weeks of age.
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ItemStudies in animal nutrition : the intake and storage of dietary nitrogen and energy( 1963)This thesis is divided into two parts. Part I consists of three chapters. Chapter 1 is a critical review of the literature which deals with the nutritional factors which influence nitrogen and energy retention in animals. In the light of these factors, the effect of dietary composition on the relative storage of energy as fat and protein is discussed. The review concludes by discussing the effect of energy storage as fat and protein on changes in liveweight. There is an extremely large volume of literature on this subject and no attempt has been made to cover it exhaustively. The more important contributions to the field have been mentioned and the review investigates the variety and complexity of nutritional factors which may influence the composition of energy storage, and discusses their likely effects. Chapter 2 describes two experiments where four diets, which differed in their levels of protein, were each fed at four levels of intake to adult guinea pigs. The effect of the level of dietary protein on the energy and nitrogen balance of the animals was investigated. Chapter 3 reports an experiment in which the change in liveweight of penned sheep, fed diets which varied in the levels of protein and energy, was interpreted in terms of the nitrogen balance of the animals and their metabolizable energy intake. The contents of Chapters 2 and 3 are to be submitted for publication shortly. Part II of the thesis consists of four published papers dealing with the food intake of grazing sheep. Chronologically the work reported in Part II preceded that reported in Part I. Chapter 4 and 5 deal with the faecal-nitrogen technique for measuring the intake of grazing sheep for both annual and perennial pastures. Chapter 6 reports the results obtained when faecal-nitrogen techniques were used to estimate the intake of a group of grazing sheep and Chapter 7 uses the results of Chapters 5 and 6 to present a hypothetical model which suggests the importance of dietary composition, with respect to digestible organic matter and digestible nitrogen, in determining the liveweight change of sheep grazing annual pastures.
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ItemThe reactions and availability of manganese in soils( 1969)The reactions of Mn in soils and the relationships between these reactions and the mechanisms of supply of Mn to plants have received attention from scientists over the last 40 years; most attention being given to the problem of Mn deficiency which occurs most commonly in soils with pH's from 6.5 to 8.0. The term "neutral" soils will be used throughout this thesis for these soils on which in deficiency occurs; the term is just as meaningful as and less cumbersome than the term "neutral and alkaline soils" which is commonly used. Some significant contributions have been made to our knowledge of the availability of In in neutral soils, but the progress has been unduly slow. It would appear that the slow progress can be partly attributed to the perpetuation of poor work, and thinking, not only by some workers in the subject, but by some writers of textbooks. This is a serious allegation to make, but when one becomes intimately involved in the subject, one is confronted with many pieces of work which are incompatible and mutually contradictory. The commonly accepted reason for In deficiency is the microbial oxidation of divalent In to higher in oxides, and yet many workers are obviously not aware of evidence which makes this conventional theory look absurd. The two simple facts that microbial oxidation of divalent Mn occurs in all neutral soils and that Mn deficiency is a "disease" of the wetter and cooler climates of the world illustrate my point precisely. This unsatisfactory situation calls for a critical appraisal of the existing theories, and in this thesis I have attempted to do this and to give a clear account of the subject. The reader will quickly find, however, that here we have a very complicated problem to which we only know some of the answers. In this thesis reference is made to some "local" soils, namely: Corny Point, Dooen, Hallam, Mt. Gambier, Penola Hill, Penola Flat, Rendelsham, University, Walpeup, Werribee, and Yambuk. And, for the convenience of the reader, some of the relevant properties of these soils are described in Part IV - Experimental Methods and Description of Soils, pp.252-255. The Introduction is not a complete review of all the work which has been done on Mn in soils. It is deliberately selective and obviously some work is irrelevant here, but some other work has been omitted either because it is mere duplication or because it does not warrant perpetuation; though possibly some work, which is relevant or otherwise, may have been overlooked. The early part of the Introduction outlines our present knowledge of the reactions and availability of in in neutral soils. This is followed by an attempt to define the nature of the root surface, a subject which has received little attention in relation to soils and has considerable relevance in the mechanism of uptake of in from neutral soils. The experimental work covers several aspects of Mn in soils, namely: the microbial oxidation of Nn, the reversion of available forms of in and the uptake of Mn by contact reduction. The results and discussions of the experiments indicate forcefully the extreme complexity of the problem of the availability of In in neutral soils. And, possibly just as important, they indicate that in a few years, one person cannot possibly solve a problem which has been baffling scientists for decades.
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ItemResearch in plant virology( 1965)
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ItemGrowth studies in beef cattle( 1962)
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