Equine Science

Zoe Davies is one of only a handful of qualified and Registered Equine Nutritionists in the UK. A former lecturer and external examiner in Equine Science, Zoe is a referral nutritionist, specialising in bloodstock and performance horses.

• Preface xxiiiAcknowledgement xxv1 The Biochemical Nature of Cells 1Metabolism 1Water 1Important Properties ofWater 4Proteins 4Basic Structure of Amino Acids 4Polypeptides 5Levels of Protein Structure 5Primary Structure of Proteins (Amino Acid Sequence) 6Secondary Structure of Proteins (Alpha Helix or Beta Pleated Sheet) 6Tertiary Structure of Proteins (3D Shape/Folding) 7Quaternary Structure of Proteins (Aggregations of Polypeptide Chains) 7Classification of Proteins 7Structure of Collagen 8Modification of Proteins 8Denaturation of Proteins 8Carbohydrates 8Fructans 9Starch 10Cellulose 11Glycogen 11Lipids/Fats 11Triglycerides 12Essential Fatty Acids 12Phospholipids 13Cholesterol 15Nucleic Acids 15Deoxyribonucleic Acid (DNA) 15Ribonucleic Acid (RNA) 16Messenger RNA (mRNA) 17Transfer RNA (tRNA) 18Ribosomal RNA (rRNA) 18Protein Synthesis 18Transcription 18Translation 20The Genetic Code 21Reading the Genetic Code 23Enzymes 23Factors that Affect the Activity of Enzymes 25Temperature 25pH 25Enzyme Concentration 25Substrate Concentration 25Cofactors and Coenzymes 25Enzyme Inhibitors 25Metabolic Poisons 26Drugs 26Summary Points 26Q + A 272 Cells, Tissues and Organs 29Cells – Building Blocks of Life 29Prokaryotic Cells 29Eukaryotic Cells 31Cell Function 31Cytoplasm 32Cytosol 32Movement of Substances in and around Cells 32Cell Organelles 32Cytoskeleton 32Cell or Plasma Membrane 33The Fluid Mosaic Model of Cell Membrane Structure 34The Role of Membranes in Cell Organelles 34Nucleus 37Endoplasmic Reticulum and Ribosomes 38Golgi Body (Dictyosome) 38Mitochondria 38Lysosomes 38Peroxisomes (Microbodies) 39Centrosomes 39Apoptosis (Programmed Cell Death) 39Cell Turnover 40Cell Division (Mitosis and Meiosis) 40The Cell Cycle 40Mitosis 41Key Events 41Cytokinesis or Cytoplasmic Division 43Meiosis 44Key Events 45First Meiotic Division 46Second Meiotic Division 46Cell Signalling 46Cell Differentiation and Stem Cells 46Blood Cell Production from Stem Cells 47Tissues and Organs 47Epithelium/Epithelial Tissue 48Epithelial Cell Shapes 50Epithelial Arrangement of Cells 50Connective Tissue 51Connective Tissue Cells 52Connective Tissue Fibres 52Tissue Repair 53The Four Stages ofWound Healing 54Stage 1 – Traumatic Inflammatory Phase 54Stage 2 – Destructive Phase (0–3 Days) 54Stage 3 – Proliferative Phase (3–24 Days) 55Stage 4 – Maturation Phase (24 Days to 2 Years) 56Ageing Tissue 56Stem Cell Therapy 56Summary Points 57Q + A 583 Equine Support and Movement 59Points of the Horse 59The Skeletal System 59Bone 59Classification of Bone Tissue 60Dense or Compact Bone 60Spongy or Cancellous Bone 61Types of Bones 61Microscopic Bone Structure 64Bone Formation and Growth 64Developmental Orthopaedic Disease 67Bone Remodelling 68Hormones and their Effect on Bone Growth 68Effect of Exercise on Bone Tissue 69Calcium Homeostasis 69Bone Fracture and Repair 69The Skeleton 70The Axial Skeleton 70The Skull 70The Vertebral Column or Spine 71The Appendicular Skeleton 75Forelimb 76Hindlimb 79Stay Apparatus 80The Mechanics of Movement 80Joints 80Types of Joints 81Movement of Joints 83Ageing of Joints 83Muscles 83CardiacMuscle 84Smooth Muscle 84Skeletal Muscle (Voluntary or Striated Muscle) 85The Sliding FilamentModel 87Muscle Anatomy 87Muscles of the Neck and Shoulder 91Brachiocephalic 91Sternocephalic 91Splenius 91Trapezius 91Rhomboideus 95Deltoideus 95Triceps 95Muscles of the Trunk 95Latissimus Dorsi 95Pectorals 95Muscles of the Forearm 95Digital Extensor 95Digital Flexor 95Muscles of the Abdomen 97Intercostal Muscles 97Longissimus Dorsi 97Muscles of the Hindlimb 97Gluteal 97Biceps Femoris 97Semitendinosus 97Digital Extensor 97Gastrocnemius 99The Importance of Muscle Fibres in Equine Performance 99Muscle Fibre Types 99Muscle Fibre Recruitment 100Fatigue 101Causes of Fatigue 101Lactic Acid Accumulation 101Summary Points 101Q + A 1014 TheLowerLimb 103Tendons and Ligaments of the Lower Limb 103Tendons 103Tendon Repair 104Extensor Tendons 106Flexor Tendons 106Ligaments and Suspensory Apparatus 106Check Ligament 106Suspensory Ligament 106Blood Supply to the Lower Leg 107The Hoof 107The Hoof as a Plastic Structure 107Effect of Movement on Hoof Structure 111Functions of the Hoof 112Shock Absorption 112Grip 112Circulation 113The External Hoof 113Wall 113Sole 116Frog 116Hoof Horn 118Internal Structures 118Digital or Plantar Cushion 118Lateral (Ungual) Cartilages 119Pedal and Navicular Bones 119The Balanced Foot 119Assessment of Foot Balance 119Static Foot Balance 119Dynamic Foot Balance 120Adaptations of Hoof Tissue 121Summary Points 121Q + A 1225 The Digestive System 123Foregut 124Mouth 124Oesophagus 127Stomach 127Gastric Juice 128Small Intestine 130Pancreas 132Endocrine Functions of the Pancreas 132Exocrine Functions of the Pancreas 133Liver 134Functions of the Liver 135Hindgut 137Large Intestine 137Caecum 137Large Colon 137Small Colon 140Rectum 140Digestion in the Large Intestine 140Equine Microbiota 140The Gut and the Immune System 142Summary Points 142Q + A 1436 The Respiratory System 145Anatomy 146Within the Head and Neck 146Within the Chest 148Blood Supply 149Pleurae 149Diaphragm 150Physiology of Respiration 150Pulmonary Ventilation 150Pressure Changes during Breathing 151Airway Resistance 151Lung Air Volumes and Capacities 151Dead Space 153Regulation of Breathing 153Respiratory–Locomotor Coupling 154External Respiration or Pulmonary Gas Exchange 155Internal Respiration or Systemic Gas Exchange 156Transport of Oxygen and Carbon Dioxide Around the Body 157Oxygen Transport 157Carbon Dioxide Transport 157The Oxygen Dissociation Curve 158The Bohr Effect 158Cellular Respiration 159Aerobic Cellular Respiration 159Aerobic Respiration of Glucose 161Glycolysis 161Link Reaction 161Krebs Cycle 163Electron Transport Chain 163Aerobic Respiration of Other Fuels 166Glycogen 166LipidMetabolism 166Protein Metabolism 167Anaerobic Respiration 167Summary Points 167Q + A 1687 The Circulatory System 169Foetal Circulation 170The Heart 171Cardiac Output 172Anatomy of the Heart 173The Cardiac Cycle 175Regulation of the Heart Beat 175The Heart and Fittening/Training Horses 176The Heart and VO2 Max 178Heart Murmurs 178Heart or Cardiac Arrhythmia 178Second-Degree AV Block 179Atrial Fibrillation (AF) 179Sudden Cardiac Death 179Blood Vessels 179Arteries 179Veins 180Capillaries 182Heart Evaluation and Examination 182Electrocardiogram 182Exercise Testing of Horses 183Blood 184Plasma 184Red Blood Cells (Erythrocytes) 185White Blood Cells (Leucocytes) 186Granulocytes 188Agranulocytes 189Platelets (Thrombocytes) 190Haemostasis or Blood Clotting 190Blood Tests 191Blood Typing 191The Lymphatic or Lymph System 192The Spleen 193Summary Points 194Q + A 1948 The Nervous System 197Nerves and Neurons 198Neuroglia or Glial Cells 200Organisation of the Nervous System 202CNS 202PNS 203Action Potential 203Resting Membrane Potential 204Synapses 206Transmission at the Synapse 207Neurotransmitters 208Endorphins and Enkephalins 208Neuromuscular Junctions 209The Brain 209Forebrain 210Hypothalamus 210Thalamus 210Cerebrum 210Midbrain 210Hindbrain 210Spinal Cord 212Reflex Actions or Arcs 212Summary Points 212Q + A 2139 The Endocrine System 215Hypothalamus 216Pituitary Gland (Hypophysis) 217Anterior Pituitary – Adenophysis 217Pars Intermedia 218Posterior Pituitary (Neurophysis) 218Thyroid Gland 219Thyroid Hormones 219Parathyroid Glands 219Adrenal Glands 220Adrenal Cortex 221Mineralocorticoids 221Glucocorticoids 222Adrenal Medulla 222Pancreas 222Secretion of Glucagon and Insulin 224Thymus 225Ovaries 225Equine Chorionic Gonadotropin 226Testes 226Pineal Gland 227The Neuroendocrine System 228Circadian Rhythms in Horses 230Sleep Patterns in Horses 231Summary Points 232Q + A 23310 The Skin 235Structure of the Skin 235Epidermis 237Stratum Basale 238Stratum Spinosum 238Stratum Granulosum 238Stratum Lucidum 238Stratum Corneum 238Dermis 238Sensation 239Melanin 239Sudoriferous Glands (Sweat Glands) 239Sebaceous Glands 239Hair 239Hair Follicles 240The Coat 241Thermoregulation 241Heat Conservation 243Heat Loss 243Sweating 245Breaking Out 246Dry Coat or Anhydrosis 246Skin and Coat Colour 246Summary Points 247Q + A 24711 The Senses 249Transduction 249Adaptation 249Somatic Receptors 250Thermal Sensations 250Pain Sensations 251Tactile Sensations 251Itch Sensation 252Proprioceptor Sensation 252Special Senses 253Sight 253Visual Streak of the Eye 253Colour Vision 254Night Vision 254Anatomy of the Eye 254Chambers of the Eye 255Photoreceptors 256Transmission of Nerve Impulses to the Brain 258Accommodation (Focusing) 258Adaptation of the Horse’s Eyes to Light 258Eyelids 259Conjunctiva 259Lacrimal Apparatus 260Hearing and Balance 260Anatomy of the Ear 261Taste and Smell 264The Olfactory System 265Jacobson’s Organ 265Summary Points 266Q + A 26612 Reproduction 267Reproductive Anatomy of the Mare 267Vulva 267Vagina 269Cervix 269Uterus 269Utero-tubular Junction 270Fallopian Tubes 270Ovaries 271The Oestrus Cycle 272Follicular Development or Oogenesis 275Ovarian Changes during the Oestrus Cycle 275Behavioural Signs of Oestrus in the Mare 276Summary of Mare Behaviour through the Cycle 276Endocrine Changes during the Oestrus Cycle 277Artificial Control of the Oestrus Cycle 278Light 279Hormonal Methods 280Postponing Ovulation 280Reproductive Anatomy of the Stallion 280Scrotum 280Testes (Testicles) 281Epididymis 282Vas Deferens 284Accessory Sex Glands 284Vesicular Gland (Seminal Vesicles) 284Prostate Gland 284Bulbo-Urethral Gland (Cowper’s Gland) 284Penis 284Spermatogenesis 285Acrosome Reaction 286Endocrine Pathways in the Male 287Fertilisation 287Pregnancy Diagnosis 287Foetal Sexing 288Twins 289Endocrine Maintenance of Gestation 289Equine Chorionic Gonadotropin 290Progesterone 290Oestrogens 290Relaxin 290Gestation 291Implantation and Placentation 291Embryology 292Phases of Equine Embryo Development and Migration 293Phase 1 294Phase 2 294Phase 3 294Phase 4 294Phase 5 294Phase 6 294Timeline of Embryonic Development 294The Foetal Endocrine System 295Preparation for Parturition (Birth) 295The Three Stages of Parturition 296Stage 1 296Stage 2 296Stage 3 296Induction 296Lactation 297Lactogenesis 297Lactation Curve 298Applied Reproductive Technologies 298Artificial Insemination 298Advantages 299Disadvantages 299Collection of Semen 299Semen Preservation 300Embryo Transfer 301Advantages 302Disadvantages 302Donor and Recipient Mares 302The Synchronisation Process 302Collection of the Embryo 302Transfer of the Embryo 303Gamete Intrafallopian Transfer 303Oocyte Transfer 303Intracytoplasmic Sperm Injection (ICSI) 303Summary Points 303Q + A 30413 Genetics 305The Genetic Code or Genome 305Chromosomes 305Gene Expression 306Mitochondrial DNA 307The Y Chromosome 308Alleles 308Dominance 308Sex Cells 309Hybrids 309Heredity 309Sex Determination 310Genotype and Phenotype 311Polygenic or Multiple Gene Traits 311Multiple Alleles 311Sex Linkage 311Lethal Genes 311Lethal White Foal Syndrome (LWFS) 311Foal Immunodeficiency Syndrome (FIS) 311Lavender Foal Syndrome (LFS) 312Severe Combined Immunodeficiency (SCID) 312Congenital Curly Coat Syndrome 312Epigenetics 312Muscle Disorders 314Nuclear Transfer (Cloning) 314Parental Similarity of Clones 314Mutation 315Gene Mutation 315Chromosome Mutation 316Non-Disjunction 316Polyploidy 316Single Nucleotide Polymorphisms 317The Myostatin Gene and Performance 317Coat Colour and Genetics 317Bay/Black 318White (Albino) (WWorWw) 318Grey (GG or Gg) 318Roan 320Spotting Patterns 320Sabino (SB1) 320Tobiano (TO or to) 320Overo (O) 320Appaloosa (LP) 320Cream (C or Ccr) 321Silver (Z) 323Champagne 323Pearl 323Dun (D or d) 323White Markings 323Melanomas in Grey Horses 323Exercise-Induced Pulmonary Haemorrhage (EIPH) or Epistaxis 323Summary Points 324Q + A 32414 The Urinary System 325Kidneys 325Nephrons 327Role of Tubules in Formation of Urine and in Homeostasis 331Proximal Convoluted Tubule 331Loop of Henle 332Distal Convoluted Tubule 333Regulation ofWater 334Regulation of Permeability of the Collecting Ducts by ADH 334Aldosterone 335Acid–Base Balance 335Extracellular and Intracellular Chemical Buffers 336Protein Buffer System 336Carbonic Acid–Bicarbonate Buffer System 336Phosphate Buffer System 336Carbon Dioxide Exhalation 337Excretion of Hydrogen Ions 337Acid–Base Imbalances 337Micturition or Urination 337Summary Points 338Q + A 33815 The Immune System 339Health Versus Disease 339Microbes 339Disease Transmission Routes 340Infection 340Biofilms 341Symptoms of Disease 341Diagnosis 342Pathogenic Organisms 342Bacteria (Prokaryotes) 342Invasive Properties 343Spread of Bacteria 344Mycoplasma Species 345Antibiotics and Resistance 345Viruses 346Structure 347Replication 348Eukaryotic Pathogens 348Fungi 348Protozoa 350Internal Parasites 351Protection from Disease 351External Barriers 351Innate Immunity 353Inflammation 353Interferons 355Complement System 356Natural Killer Cells 356Adaptive/Acquired Immunity 357Types of Adaptive/Acquired Immunity 357Antigens and Antibodies 361Antigen Presentation 362Ingestion of an Antigen – Mode of Action 362T Cells and Cell-Mediated Immunity 363Helper T Cell Activation 363Cytotoxic T Cells 363Summary Points 364Q + A 36416 Exercise Physiology, Functional Anatomy and Conformation 365Exercise Physiology 365Fitness 365Horses at Rest 365Exercise 365Exercise and Energy 366Fuels Available for Exercise 367Immediate Response of the Horse’s Body to Exercise 368Changes Occurring during Exercise 368Homeostatic Mechanisms Involved during Exercise 369LactateThreshold 370Over-training 370Recovery 370Long-Term Responses of the Horse’s Body to Exercise 371Fitness Training 373PreliminaryWork 373DevelopmentWork 374FastWork 374Interval Training 374Aims of Interval Training 374Monitoring Interval Training 375Beginning Interval Training 375How to Use Interval Training 375Points Regarding Interval Training 375Functional Anatomy 376Centre of Gravity 376Stay Apparatus 377Moving the Front Legs 380Moving the Hind Legs 380Equine Biomechanics 381Kinematics 381Kinetics 381Conformation 382Ideal Conformation 382Head 382Topline 382Neck 382Withers 384Chest 384Shoulder 384Elbow 384Forelimb 385Feet 386Back 386Hindquarters 387Summary Points 390Q + A 39017 Teeth and Ageing 391Equine Teeth 391Wear and Tear 394Ageing 396Care of Equine Teeth 399Summary Points 401Q + A 40118 Evolution, Classification and Behaviour of the Horse 403Evolutionary Time Period 403Classification 403Species 404Evolutionary Development 407The Evolutionary Family Tree 409Domestic Breeds and Types of Horses 412Donkeys 412Przewalski’s Horse 412Mustangs 414Behaviour of the Modern Horse 414Innate Behaviour 414Learned Behaviour 415Habituation 415Classical Conditioning 416Operant Conditioning 416Latent Learning 416Insight Learning 416Stereotypies 416Imprinting 417The Dopamine Receptor D4 417Emotion 417Summary Points 417Q + A 418A Anatomical Terms Based on theMedian Plane 419B Haematology and Plasma Biochemistry Tests 421C Functions, Sources and Deficiencies of Vitamins andMinerals in Horses 423Index 429