Growth of Farm Animals

360 Pages·2002·4.596 MB·English

by  T. L. J. Lawrence, V. R. Fowler

Growth of Farm Animals
Second Edition
Dedication
To our wives, Elizabeth Ray Lawrence and Janet Fowler, for their continued help
and forbearance in the writing of this second edition.
Growth of Farm Animals
Second edition
T.L.J. Lawrence
formerly of the
Faculty of Veterinary Science
University of Liverpool
UK
and
V.R. Fowler
formerly of the
Scottish Agricultural College
and of the Rowett Research Institute
Aberdeen
UK
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A catalogue record for this book is available from the British Library,
London, UK.
Library of Congress Cataloging-in-Publication Data
Lawrence, T.L.J. (Tony Leonard John)
Growth of farm animals / T.L.J. Lawrence and V.R. Fowler.--2nd ed.
p. cm.
Includes bibliographical references and index.
ISBN 0-85199-484-9 (alk paper)
1. Livestock--Growth. 2. Veterinary physiology. I. Fowler, V.R.,
II. Title.
SF768.L39 2002
2002004672
ISBN 0 85199 484 9
Typeset by Columns Design Ltd, Reading
Printed and bound in the UK by Cromwell Press, Trowbridge
Contents
Preface to First Edition xi
Preface to Second Edition xii
1 General Aspects of Growth 1
1.1. Introduction 1
1.2. Being the Right Size 1
1.3. Why Do Animals Change in Form as They Grow? 2
1.3.1. Growth of the eye 3
1.3.2. Growth of wings 4
1.3.3. The pinna of the ear 4
1.4. Shape and Mass 4
1.5. Domestication and Size of Animal 5
1.6. Growth and Form 6
1.7. Domestication and Growth 6
References 6
2 Cells 7
2.1. Introduction 7
2.2. Cell Structure 7
2.2.1. General 7
2.2.2. The nucleus 8
2.2.3. The cytoplasm 9
2.3. Chemical Composition of Cells 10
2.3.1. General 10
2.3.2. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) 11
2.4. Protein Synthesis and the Genetic Code 13
2.5. The Cell Cycle 14
2.6. Cellular Proliferation 16
2.7. Cell Hyperplasia and Hypertrophy 19
References 20
3 Tissues: Basic Structure and Growth 21
3.1. Introduction 21
3.2. Nervous Tissue 21
3.2.1. Introduction 21
v
vi Contents
3.2.2. Structure of basic tissue: cells and fibres 21
3.2.3. Major divisions and development of the nervous system 23
3.3. Connective Tissue 23
3.3.1. Structure and classification 23
3.3.2. Supportive connective tissue 27
3.3.3. Haemopoietic connective tissue 38
3.3.4. Loose connective tissue 38
3.4. Muscle Tissue 56
3.4.1. Introduction 56
3.4.2. Structure 56
3.4.3. Types 63
3.4.4. Chemical composition of muscles 65
3.4.5. Muscle growth 67
3.5 Epithelial Tissue 76
3.5.1. Types and structure 76
3.5.2. Integument 77
3.5.3. Hair and wool 77
References 83
4 Tissues: Growth and Structure Relative to Product Value for Human Consumption 86
4.1. Introduction 86
4.2. Carcass Yield, Composition and Quality 86
4.3. Carcass Tissues and Concepts of Meat Quality 90
4.3.1. General 90
4.3.2. From muscle in the live animal to lean meat in the carcass 90
4.3.3. From adipose tissue in the live animal to fat in the carcass 96
4.4. Fibre Yield and Quality 98
4.4.1. General 98
4.4.2. Wool 98
4.4.3. Goat hair 100
References 101
5 Mammary Gland Growth and Product Yield 103
5.1. Introduction 103
5.2. Mammary Gland Structure 103
5.3. Morphogenesis 104
5.3.1. General features 104
5.3.2. Measurement of growth and size 105
5.3.3. Prenatal period 106
5.3.4. Birth 110
5.3.5. Prepubertal period 111
5.3.6. Growth during recurring oestrous cycles 111
5.3.7. Changes during pregnancy 111
5.3.8. Growth at parturition, during lactation and at involution 112
5.3.9. Effects of external factors 112
5.4. Products of the Mammary Gland 114
5.4.1. General 114
5.4.2. Nutrient composition of colostrum and milk 115
5.4.3. Nutrient content and growth of sucking animals 117
References 118
Contents vii
6 Hormonal Influences on Growth 120
6.1. Introduction 120
6.2. Hormones 120
6.2.1. Hormones and metabolism: modes of action 120
6.2.2. Individual hormones and growth 123
6.2.3. Hormones and the control of food intake 139
6.2.4. Hormones and the photoperiodic control of growth 140
References 143
7 Genetic Influences on Growth 146
7.1. Introduction 146
7.2. Heritability of Growth and Growth-related Traits 146
7.2.1. Introduction 146
7.2.2. Selection differential, generation interval and genetic gain 149
7.2.3. Repeatability and breeding value 151
7.3. Hybrid Vigour 151
7.4. Undesirable Genetic Effects on Growth and Related Traits 153
7.5. Breeds 155
7.6. Biochemical and Physiological Considerations of Gene Action in Growth 155
References 158
8 The Immune System and Growth 160
8.1. Introduction 160
8.2. The Immune System, Disease and Growth 160
8.3. Endocrine and Immune System Interactions 163
8.4. The Immune System and Manipulation of Endocrine Function 164
References 167
9 Gametes, Fertilization and Embryonic Growth 168
9.1. Introduction 168
9.2. Meiosis, Gametes and Fertilization 168
9.2.1. Introduction 168
9.2.2. Meiosis and gametogenesis 169
9.2.3. Gametes and fertilization 173
9.3. Embryonic Development 176
9.3.1. Cleavage 176
9.3.2. Blastocyst formation and hatching 178
9.3.3. Gastrulation and tubulation 180
9.4. The Uterus, the Placenta and Embryonic Attachment 182
9.4.1. The uterus 182
9.4.2. The placenta and embryonic attachment 183
9.5. Post-gastrulation and Post-tubulation Embryonic Development 188
9.6. New Technologies and Embryo Growth 189
9.6.1. Techniques 189
9.6.2. Embryo growth 190
References 191
10 Prenatal and Postnatal Growth 193
10.1. Problems of Describing Growth 193
10.1.1. Growth in relation to time 193
viii Contents
10.2. Describing Prenatal and Postnatal Growth 196
10.3. Targets of Growth 197
10.4. Sequential Growth Targets 198
10.5. Changes in Proportion During Growth 201
10.5.1. Changes in proportion during prenatal growth 202
10.5.2. Size at birth 205
10.5.3. The first controversy: live weight as a determining variable 206
10.5.4. The second controversy: should fat be included as part of
the independent variable? 208
10.6. Functional Units 209
10.7. Tissue Proportions: Breed and Slaughter Weight 211
10.8. Conclusions 214
References 215
11 Efficiency and Growth 216
11.1. Numerical Concepts of Efficiency 216
11.2. Energy as a Baseline for Feed Input 217
11.3. Units of Energy 217
11.3.1. The joule 217
11.3.2. The calorie 217
11.4. The Gross Energy of a Feed 218
11.5. Definitions of Feed Energy in Animal Systems 219
11.6. The Partition of Metabolizable Energy in the Growing Animal 220
11.7. Maintenance and Basal Metabolism 221
11.8. The Utilization of Dietary Energy above Maintenance 222
11.9. Growth Rate, Feed Intake and Efficiency 224
11.10. The Effect of Choice of Slaughter Weight on Efficiency 225
11.11. Once-bred Gilts and Once-bred Heifers 227
11.12. Efficiency, Slaughter Weight and Marketing 228
References 228
12 Compensatory Growth 229
12.1. Introduction 229
12.2. Factors Affecting Compensatory Growth 230
12.2.1. General factors 230
12.2.2. Animal factors 231
12.2.3. Nutritional factors 234
12.3. Components of Compensatory Growth 239
12.3.1. General 239
12.3.2. Changes in tissue proportions 240
12.4. Compensatory Growth and Overall Efficiency 248
12.5. Compensatory Growth: Problems of Interpretation 249
References 253
13 Growth and Puberty in Breeding Animals 255
13.1. Introduction 255
13.2. The Endocrinology of Puberty 256
13.3. Factors Affecting Puberty 256
13.4. Effects of Growth Rate on Puberty 257
13.4.1. General 257
13.4.2. Cattle 258
Contents ix
13.4.3. Pigs 263
13.4.4. Sheep 266
13.4.5. Horses 270
13.4.6. Poultry 271
References 275
14 Measuring Growth 277
14.1 Introduction 277
14.2. Measurements on the Live Animal 277
14.2.1. Live weight 277
14.2.2. Body measurements 280
14.2.3. Visual appraisal of live animal conformation 286
14.2.4. Dilution techniques 288
14.2.5. Neutron activation analysis 289
14.2.6. Probes 290
14.2.7. Balance studies 290
14.2.8. X-ray and computed tomography 291
14.2.9. Nuclear magnetic resonance 291
14.2.10. Ultrasonic techniques 295
14.2.11. Bioelectrical impedance analysis 299
14.2.12. Video image analysis 299
14.2.13. Cell size in adipose tissue 300
14.2.14. Urinary creatinine excretion 300
14.3. Measurements on the Carcass 300
14.3.1. General 300
14.3.2. Carcass weight and killing-out (or dressing-out) proportion 301
14.3.3. Specific gravity or density 302
14.3.4. Measurements taken by ruler and by probe 302
14.3.5. Visual appraisal (scoring) 309
14.3.6. Jointing and dissection techniques 312
14.3.7. Ultrasonic devices 315
14.3.8. Video image analysis 316
14.3.9. Bioelectrical impedance analysis 316
14.3.10. Electromagnetic scanning 317
References 317
15 ‘Growth Promoters’, Performance Enhancers, Feed Additives
and Alternative Approaches 320
15.1. Introduction 320
15.2. Classification of Growth Promoters and Performance Enhancers 320
15.3 Historical Note 321
15.3.1. Discovery 321
15.3.2. Concerns 322
15.3.3. The situation from 1999 322
15.3.4. How do antibiotics and antibacterials work? 323
15.4. Additives with the Potential to Replace Antibiotics in the Feeds
of Pigs and Pre-ruminant Ruminants 323
15.4.1. Probiotics 323
15.4.2. Chemical probiosis 323
15.4.3. Diet pre-fermentation 324
15.4.4. Organic acids 324