G. Dryden - Animal Nutrition Science

Animal Nutrition Science

Gordon McL. Dryden

Senior Lecturer in Animal Nutrition
School of Animal Studies
The University of Queensland, Gatton
Australia

CABI is a trading name of CAB International

G.McL. Dryden 2008. All rights reserved. No part of this publication may be reproduced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners.

A catalogue record for this book is available from the British Library, London, UK.

Library of Congress Cataloging-in-Publication Data

Dryden, Gordon McL.

Animal nutrition science / Gordon McL. Dryden.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-84593-412-5 (alk. paper)

1. Animal nutrition--Textbooks. I. Title.

SF95.D79 2008

636.08'52--dc22

2007050644

ISBN: 978 1 84593 412 5

Typeset by SPi, Pondicherry, India.

Printed and bound in the UK by Cambridge University Press, Cambridge.

Every reasonable effort has been made to obtain and evaluate information from a wide variety of reputable sources and to ensure its accuracy at the time of writing. Nevertheless the author and publisher disclaim all responsibility for any liability, loss, injury or damage incurred as a consequence, directly or indirectly, of the use and application of any of the contents of this volume.

Animal nutrition is one of the most diverse disciplines in the animal sciences. Its sub-disciplines range from the biochemistry of nutrient use and digestive physiology, through nutritional genomics and the mathematical modelling of nutrient requirements, to the ongoing development and refinement of animal feeding systems. There are two reasonably distinct areas of study: the first is the basic biochemistry and physiology of the discipline and the second involves the application of these concepts to the design of feeding systems. These two areas are usually considered separately. This is not because one is scientific and the other practical (an incorrect and sterile distinction), but because the biochemical and physiological topics are general in nature, while studies of feeding systems must, necessarily, be focused on each animal type and the relevant welfare, production and economic considerations.

This book describes how animals obtain, digest and use food and nutrients, how their nutrient requirements can be quantified and how nutrient use can affect the environment. The discussion is not confined to any particular type of animal domestic or wild, ruminants or monogastrics. The book is intended for senior undergraduate or postgraduate readers, and so it assumes a basic understanding of intermediary metabolism and digestive physiology and anatomy. The structure of the text is illustrated in where the 18 topics are grouped to show how they relate to each other.

We begin in with a discussion of nutritional ecology, the study of how animals obtain and digest their food. This is an important part of animal nutrition, although it is not often included in nutrition texts. There are important differences in abilities to prehend and digest food, and in food preferences, and these determine the characteristics of feeding systems for different animals.

The second major topic ( thus form a group which deals with food composition, nutritive value and safety.

Digestion determines the nutrients which become available to the animal (). If intestinal digestion occurs before microbial digestion, then the absorbed nutrients will reflect, fairly accurately, the composition of those constituents in the food. If microbial fermentation comes first, then the composition of the absorbed digestion products is usually quite different to the food. Of course, ruminants do have some advantages they are more resistant to food-borne toxins than monogastric animals, and they have more flexibility in their requirements for some nutrients. The distinction between foregut fermentation and other types of digestive systems is important, and it informs the design of feeding systems and our expectations about animal product quality.

The functions, sources and metabolism of minerals, vitamins and water are discussed in . The metabolic roles of these nutrients, and the quantification of animals requirements for them, are active fields of study. Examples of new information are the roles of vitamin D in controlling cell proliferation and differentiation and quantitative data about the water requirements and salinity tolerances of horses and deer.

neuro-hormonal systems is important in all animals, while digestive tract control is also important in ruminants, as the escape of undigested food from the rumen influences how much food these animals can eat.

Fig. P.1. Nutritional factors which affect animal production and welfare (topic numbers refer to the chapters in this book).

Energy and protein requirements, and how these change with production type and rate, are discussed in , is the practical application of nutrient requirement data. Conventional methods optimize rations for a set of outcomes (e.g. least cost, or minimum nutrient excretion), while mathematical models of nutrient use describe the interplay of variables such as animal type and environmental factors, and can answer what if? questions.

We may need to investigate situations where we think that our animal is incorrectly fed. The nature of the problem may be only apparent after careful examination. Objective procedures which can be used to investigate nutritional problems are described in .

The intensification of animal production has led to an increasing problem of nutrient wastage and environmental pollution, and considers how the animals genotype influences its nutrient requirements. With modern genetic technologies we can move past empirical observations that there are differences between genotypes, and we can now explain in detail how genotype influences an animals ability to utilize nutrients. In the future we will be able to develop feeding systems tailored to individual animals genotypes (this is already beginning to be done in human nutrition).

Food processing, the animals response to this and the procedures needed for it are described in

Parts of this book were reviewed by Michael Evans (Applied Nutrition), Brenton Hosking (Better Blend Stockfeeds), Simone Hoskin (Massey University), Andr-Denis Wright (CSIRO), Rafat Al Jassim, John Gaughan, Patrick Moss, Clive Phillips and Dennis Poppi (The University of Queensland). I am grateful for their very helpful comments. Of course, any errors of omission or interpretation are mine.