School of Agriculture, Food and Ecosystem Sciences - Theses
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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 digestion of ruminant feeds in vitro( 1974)Systems of feed evaluation require the determination of the digestibility of the components of the feeds. The determination of digestibility in vivo is laborious and expensive, thus considerable research effort has been directed towards the determination of techniques to measure digestibility in vitro. The development of laboratory methods for assessing the digestibility of ruminant feeds is discussed. A two- stage technique, composed of microbial and enzymatic digestion stages, has currently been applied to the analysis of herbages, mixed forages, wood, brassicas, concentrates and silages. The digestibility of substrates determined by means of the two-stage in vitro method may be affected by the method of preparation of the substrate, the pH and duration of the microbial digestion, and the ratio of the rumen fluid to the buffer solution. The source of the rumen fluid may also affect digestibility in vitro , since the activity of this. fluid varies between species, individuals within species and the diet of the donor animals. Variation due to the diet of the donor may be minimized by means of a diet with an adequate crude protein content. Regression analyses are presented relating in vivo digestibilities to values of digestibility estimated by various laboratory procedures. In vivo digestibility may be predicted more accurately by the in vitro digestibility technique than by the nylon bag technique or by chemical methods of evaluation. However, methods incorporating the digestibility of cell wall material, digestion by fungal cellulase or summative equations of chemical constituents may be used as alternatives to the two-stage digestibility technique. The review is concluded with a discussion of the relationships between in vitro digestibility values of feeds and the values of total digestible nutrients, index of nutritive value, starch equivalent, voluntary intake, digestible energy and metabolizable energy , the last two of which are currently used to formulate rations for ruminants.