INTRODUCTORY ANIMAL PRODUCTION Giới thiệu về sản xuất chăn nuôi TLTA

This course is designed to introduce students to basic concepts and principles of animal science and their application in animal agriculture. The objective of the course is to help the student to:  Develop an overview of the nature of animals and animal production,  Become familiar with terminology used in animal science as it relates to the industry, management practices, equipment and animals,  Develop an understanding of animal species and breeds that compromise the livestock production and their relative importance from economic and social perspectives,  Develop a basic understading of the value and contributions which animals can contribute to the human needs,  Develop a basic understanding of animal genetics and breeding, animal nutrition, and reproduction, behaviour and welfare,  Develop a basic understanding of current management practices as it relates to raising the common farm animal species, viz. swine, poultry, and cattle. The primary compensation for students taking this course is that they will

INTRODUCTORY ANIMAL PRODUCTION

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TABLE OF CONTENTS

INTRODUCTION 5

Chapter 1 THE SOCIO-ECONOMIC VALUE AND CONTRIBUTIONS OF ANIMALS 6

1.1 Basic concepts 6

1.1.1 Animals 6

1.1.2 Animal science 6

1.1.3 Animal production 7

1.2 The value of animals to mankind 8

1.2.1 Consumables (food) 8

1.2.2 Convertibles (materials) 8

1.2.3 Draught power 9

1.2.4 Other contributions 9

1.3 Animal production in food security and sustainable agriculture 11

1.3.1 Animal production and food security 11

1.3.2 Animal production and sustainable agriculture 11

Chapter 2 ANIMAL GENETICS AND BREEDING 15

2.1 Fundamental principles of genetics 15

2.1.1 Transmission Genetics 15

2.1.2 Molecular Genetics 16

2.1.3 Population Genetics 17

2.2 Animal selection 19

2.2.1 Purpose of animal selection 19

2.2.2 Methods of animal selection 19

2.3 Breeding schemes 19

2.3.1 Purebreeding 19

2.3.2 Crossbreeding 21

Chapter 3 ANIMAL REPRODUCTION 25

3.1 Reproductivion in mammalian animals 25

3.1.1 The reproductive systems 25

3.1.2 Reproductive processes 26

3.2 Reproduction in poultry 31

3.2.1 The reproductive system 31

3.2.2 Puberty 32

3.2.3 Breeding 32

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3.4 Reproductive technology 33

3.4.1 Artificial insemination (AI) 33

3.3.2 Embryo transfer (ET) 34

Chapter 4 ANIMAL NUTRITION AND FEEDING 36

4.1 Nutrients and their functions 36

4.1.1 Water 36

4.1.2 Protein 37

4.1.3 Carbohydrates 38

4.1.4 Fats 39

4.1.5 Minerals 39

4.1.6 Vitamins 40

4.2 Nutrient requirements 40

4.3 Feed 41

4.4 Ration and diet 42

4.5 Digestion and metabolism 43

4.5.1 Digestion 43

4.5.2 Metabolism 46

Chapter 5 ANIMAL BEHAVIOUR AND WELFARE 47

5.1 Animal behaviour 47

5.1.1 Introduction to animal behaviour 47

5.1.2 Types of behaviour in farm animals 48

5.2 Animal wefare 52

5.2.1 Concepts of animal welfare 52

5.2.2 Assessment of animal welfare 53

5.2.3 Welfare of farm animals 55

Chapter 6 ANIMAL HEALTH 57

6.1 Basic animal health concepts 57

6.1.1 Animal disease 57

6.1.2 Transmission of animal diseases 58

6.1.3 The immune system and immunity 59

6.2 Animal disease prevention 60

6.2.1 On-farm biosecuruty 60

6.2.2 Vaccination programs 61

6.2.3 Herd/flock health management 61

6.3 Animal disease control 62

6.3.1 Animal disease monitoring and surveillance 62

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6.3.2 Treatment of diseased animals 63

6.3.3 Control of animal disease outbreaks 64

6.4 Socio-economic impacts of animal diseases 65

6.4.1 Animal diseases and human health 65

6.4.2 Animal health economics 66

Chapter 7 SWINE PRODUCTION 68

7.1 Swine breeds 68

7.1.1 Local pig breeds of Vietnam 68

7.1.2 Exotic swine breeds 70

7.2 Swine production cycle and pork chain 72

7.2.1 Swine production cycle 72

7.2.2 Pork chain 74

7.3 Swine production systems 76

7.4.1 Farrow-to-finish systems 77

7.4.2 Farrow-to-feeder systems 78

7.4.3 Feeder-to-finish systems 78

Chapter 8 POULTRY PRODUCTION 80

8.1 Types of chicken breeds 80

8.1.1 Egg laying chickens 80

8.1.2 Meat chickens 80

8.2 Production cycle of chicken farming systems 81

8.2.1 Breeder farm cycle 81

8.2.2 Layer farm cycle 83

8.2.3 Meat chicken farm cycle 84

8.3 The principles of poultry husbandry 86

8.3.1 Use of good quality and right class of stock 87

8.3.2 Provision of good housing 87

8.3.3 Maintanance of good health 88

8.3.4 Nutrition for economic performance 89

8.3.5 Good stockpersonship 90

8.3.6 Maximum use of management techiniqes 90

8.3.7 Use of records 91

8.3.8 Good marketing practice 91

Chapter 9 BEEF CATTLE PRODUCTION 92

9.1 Beef cattle breeds 92

9.1.1 Temperate beef cattle breeds 92

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9.1.2 Tropical beef cattle breeds 93

9.2 Beef cattle production cycle and beef chain 95

9.2.1 Beef cattle production cycle 95

9.2.2 Beef chain 96

9.3 Beef production systems 97

9.3.1 Extensive systems 97

9.3.2 Mixed farming systems 97

9.3.3 Intensive specialised systems 98

9.3.4 Beef cattle production systems in Vietnam 99

Chapter 10 DAIRY CATTLE PRODUCTION 101

10.1 Dairy cattle breeds 101

10.1.1 Temperate dairy cattle breeds 101

10.1.2 Tropical dairy cattle breeds 102

10.2 Dairy cattle production cycle and milk chain 102

10.2.1 Dairy cattle production cycle 102

10.2.2 Milk commodity chain 104

8.3 Dairy farming systems 107

8.3.1 General chracteristics of dairy farming systems 107

8.3.2 Types of dairy farming systems 107

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INTRODUCTION

This course is designed to introduce students to basic concepts and principles of animal science and their application in animal agriculture The objective of the course is to help the student to:

 Develop an overview of the nature of animals and animal production,

 Become familiar with terminology used in animal science as it relates to the industry, management practices, equipment and animals,

 Develop an understanding of animal species and breeds that compromise the livestock production and their relative importance from economic and social perspectives,

 Develop a basic understading of the value and contributions which animals can contribute to the human needs,

 Develop a basic understanding of animal genetics and breeding, animal nutrition, and reproduction, behaviour and welfare,

 Develop a basic understanding of current management practices as it relates to raising

the common farm animal species, viz swine, poultry, and cattle

The primary compensation for students taking this course is that they will have an invaluable knowledge of the basics of animal agriculture The knowledge attained and retained will not only help the student become better prepared for their professions, but also they will become well-informed consumers for the remainder of their life

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Chapter 1

THE SOCIO-ECONOMIC VALUE AND CONTRIBUTIONS OF ANIMALS

Humans keep domesticated animals because they provide something of value Animal products provide one-sixth of human food energy and more than one-third of the protein on a global basis Animals make many additional contributions to the well-being of humans and the society Ultimately food supply and other aspects of quality of life for all people are very much dependent

on animals This chapter is about basic concepts related to animals and their socio-economic contributions.

of adaptations for successful life under all sorts of conditions, so that there are now more kinds

of animals than of all other living things combined

Livestock is a nebulous term and may be defined narrowly or broadly On a broader view,

livestock refers to any breed or population of animal kept by humans for a useful, commercial purpose This can mean domestic animals, semi-domestic animals, or captive wild animals Semi-domesticated refers to animals which are only lightly domesticated or of disputed status These populations may also be in the process of domestication Some people may use the term livestock to refer just to domestic animals or even just to red meat animals The term as usually used does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning of 'livestock' is common

1.1.2 Animal science

Animal science is described as "studying the biology of animals that are under the control of

mankind" Historically the animals studied were farm animals but courses available now look at

a far broader area to include companion animals for example dogs, cats, horses and captive animals The study of animal science is now concerned with the scientific understanding of how animals work: from the physiology and biochemistry of tissues and major organ systems down to the structure and function of biomolecules and cells Where particular emphasis is given to the

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study of growth, reproduction, nutrition and lactation of farm and companion animals and how these processes may be optimised to improve animal productivity, health and welfare

1.1.3 Animal production

Animal husbandry, also called stockbreeding, is the agricultural practice of breeding and

raising animals/livestock Raising animals is an important component of modern agriculture It has been practiced in many societies, since the transition to farming from hunter-gather lifestyles Farming practices vary dramatically worldwide and between types of animals Livestock are generally kept in an enclosure, are fed by human-provided feed and are intentionally bred, but some livestock are not enclosed, or are fed by access to natural feeds, or are allowed to breed freely, or any combination thereof

Livestock raising historically was part of a nomadic or pastoral form of material culture The enclosure of livestock in pastures and barns is a relatively new development in the history of agriculture When cattle are enclosed, the type of ‘enclosure’ may vary from a small crate, a large fenced pasture or a paddock The type of feed may vary from natural growing grass, to highly sophisticated processed feed Animals are usually intentionally bred through artificial insemination or through supervised mating Indoor production systems are generally used only for pigs and poultry, as well as for veal cattle Indoor animals are generally farmed intensively,

as large space requirements would make indoor farming unprofitable and impossible However, indoor farming systems are controversial due to: the waste they produce, odour problems, the potential for groundwater contamination and animal welfare concerns

Other livestock are farmed outside, although the size of enclosure and level of supervision may vary In large open ranges animals may be only occasionally inspected or yarded in "round-ups"

or a muster (livestock) Working dogs such as sheep dogs and cattle dogs may be used for mustering livestock as are cowboys, stockmen and jackaroos on horses, or with vehicles and also

by helicopters Since the advent of barbed wire (in the 1870s) and electric fence technology, fencing pastures has become much more feasible and pasture management simplified Rotation

of pasturage is a modern technique for improving nutrition and health while avoiding environmental damage to the land In some cases very large numbers of animals may be kept in indoor or outdoor feeding operations (on feedlots), where the animals' feed is processed, offsite

or onsite, and stored on site then fed to the animals

Animal production is the technology applied to the keeping of animals for profit It includes

feeding, breeding, housing and marketing

Industrial animal production is a modern form of intensive farming that refers to the

industrialized production of livestock, including cattle, poultry (in "battery farms") and fish Most of the meat, dairy and eggs available in supermarkets are produced by industrialized agriculture Confined industrial animal agriculture of livestock and poultry are commonly

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referred to as factory farming and are criticised by opponents for the low level of animal welfare standards and associated pollution and health issues

1.2 The value of animals to mankind

Humans keep domesticated animals because they provide something of value We can divide animal contributions to mankind into different categories as follows

1.2.1 Consumables (food)

Livestock's most universal and significant productivity is in terms of milk, meat and/or eggs for direct consumption by the animal owners or for sale to others Diets based on meat, eggs and dairy products contain proteins, carbohydrates, fats, minerals and vitamins present in appropriate amounts and readily digestible forms to meet all human nutritional requirements

Mammalian species such as cattle, pigs, goats, sheep, equines, yaks, cameloids, buffaloes, reindeer and poultry yield substantial consumable commodities The number of contributors becomes larger when exotic birds such as ostriches, guinea fowl, pheasants, quail, pigeons and Cornish hens are included and expands even further with poikilotherms such as fresh or salt water fish, shrimp, lobsters, crabs, oysters, mussels, squid, clams, scallops, frogs, turtles and even honey bees The total contributions from domesticated animals, while not approaching the proportions derived from plants, are still quite large, providing approximately 34% of human food protein and 16% of food energy supply

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1.2.3 Draught power

Animals can be trained to perform a great variety of tasks, especially for draff power This is done by conditioning them – rewarding them for correct behaviour Cattle, buffaloes, horses, donkeys, mules, reindeer, yaks, elephants, dogs, camels and other cameloids all provide draft power for plowing, harvesting, transportation, lifting water and skidding logs

Since the dawn of humanity, animals have been used for work, be it for agricultural production

or for improving social status But over the past century, with increasing mechanisation, the animal work force has dwindled in developed countries, whereas they still contribute enormously towards fuel energy economy in most developing countries Although machines deriving energy from fossil fuels replaced draft animals in some regions, mechanization is too expensive or not suited to many cultivated terrains Thus, motive power will continue to be important throughout the developing world and might be revived to some extent even in industrialized countries

1.2.4 Other contributions

Animals are also used by humans in a number of other ways:

Recreation, warship and companionship

Animals in sport, warship, companionship, ceremonies and leisure are all very important aspects

of human association with animals However, none of these is free of ethical implication Much

of the debate centres on the extent of the exploitation of animals Some people argue the specially bred animals enjoy what people get them to do, but others might say that the animals have no choice

Fashion

Throughout history, fur has been seen as a luxury item of clothing, conferring high status on its wearer Opponents of the fur trade have engaged in direct action for many years, and have had a high level of publicity This has meant that fur has become less fashionable since people’s awareness of animal welfare and conservation issues has been raised

Health research

There are three main types of scientific research in which animals can be used:

 “Pure” research: basic investigation into aspects of the biochemistry, physiology and anatomy usually of mammals for biomedical research

 Research into the causes and treatment of disease: investigation into pathological biochemistry, and physiology

 Testing of products for safety of use

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Biological control

The grazing of livestock is sometimes used as a way to control weeds and undergrowth For example, in areas prone to wild fires, goats and sheep are set to graze on dry scrub which removes combustible material and reduces the risk of fires Sheep have also been used to control weeds in sugar cane fields, lowering the cost of herbicides, and providing an additional income from meat production Such systems also safeguard the environment and avoid chemical pollution while supplying additional organic material to the soil

Income and security

Livestock production is a major component of the agricultural economy of developing countries and goes well beyond direct food production Sales of livestock and their products provide direct cash income to farmers In fact, livestock are often the most important cash crop in many small holder mixed farming systems This source of disposable income is important for purchase of agricultural inputs and other family needs

Livestock give increased economic stability to farm households, acting as a cash buffer (small stock), a capital reserve (large animals) and as a hedge against inflation In mixed farming systems, livestock reduce the risk through diversification of production and income sources and there is therefore a much greater ability to deal with seasonal crop failures and other natural calamities Livestock represent liquid assets which can be realized at any time, adding further stability to the production system Livestock are the living bank for many farmers for whom animal ownership ensures varying degrees of sustainable farming and economic stability

Employment

Increased production implies higher employment Dairying is labour intensive at farm level and women are active in production and marketing Labour typically amounts to over 40 per cent of total costs in small harder systems Goats, sheep, poultry and rabbits, and especially from backyard production systems, are an important source of part-time work, particularly for landless women and children

The processing sector has also been identified as a focus for generating employment and limiting rural depopulation Small scale milk processing and marketing is labour intensive (50-100 kg per workday) and generates employment (and income) from local manufacture of at least part of the equipment used The meat sector also provides employment for slaughter, marketing and processing

Recycling

Different types of by-products can be efficiently recycled by animals Slaughterhouse wastes, when adequately processed, are useful protein (offals and viscera) and mineral (bones) supplements in animal feeds Household wastes are commonly fed to pigs and small animals in

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backyard systems in developing countries In urban and periurban areas, restaurant and catering wastes can easily be processed for pigs Industrial fish waste creates pollution around canning plants It is usual to dry it, at very high cost, for fish meal for export to developed countries Preservation of fish waste in molasses for feeding has been shown to be technically and economically feasible for use by poor farmers

1.3 Animal production in food security and sustainable agriculture

As mentioned above, livestock have multipurpose contributions to food and agricultural production and thus live stock production has both direct and indirect contributions to food security and sustainable development in the developing countries

1.3.1 Animal production and food security

If food security is defined as " access to enough food for an active healthy life" livestock can make a major contribution Livestock may contribute to food security through increased output

of livestock and non-livestock products and by employment and income generation that may assure access to food An adequate quantity of balanced and nutritious food is a primary indicator of quality of life, human welfare and development Animals are an important source of food, particularly of high quality protein, minerals, vitamins and micronutrients Quality foods derived from animal sources have major importance for optimizing human performance in chronically mild to moderately malnourished populations This is especially important for young children

Increased livestock production in developing countries may add to food security in several ways:

- First, many poor small holders will have direct access to more food of livestock origin

- Second, increased production will keep livestock product prices down and allow low income groups access to such food Producers should gain in the face of lower prices because livestock products are both price and income elastic, so lower prices should increase demand, total production and farm revenue In many countries, low income people suffer more from energy than they do from protein deficiency Increased production and low prices may allow consumers on low incomes to increase consumption of livestock products and help overcome the energy-protein deficiency simultaneously

- Third, increased domestic production will reduce imports and save foreign exchange which can then be diverted to productive investment and indirectly contribute to food security Some countries generate revenue by taxing imported goods including animal products Taxing increased income from domestic production may serve the same purpose

1.3.2 Animal production and sustainable agriculture

Sustainable agriculture refers to the ability of a farm to produce food indefinitely, without

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causing severe or irreversible damage to ecosystem health Two key issues are biophysical (the long-term effects of various practices on soil properties and processes essential for crop productivity) and socio-economic (the long-term ability of farmers to obtain inputs and manage resources such as labor)

Sustainable agriculture integrates three main goals: environmental stewardship, farm profitability, and prosperous farming communities These goals have been defined by a variety

of disciplines and may be looked at from the vantage point of the farmer or the consumer

Sustainable agricultural systems involve animals for their unique ability to use noncompetitive, nonrenewable resources, and for their integration with other farm practices They complement plant production systems, and provide biological and economic diversity Management of such mixed or integrated systems is the greatest challenge

Integrating livestock and agriculture increases short term benefits to and long term sustainability

of agriculture Nutrient recycling is an essential part of any strategy for sustainable agriculture Integration of livestock and crops allows for efficient recycling through use of crop residues and by-products as animal feeds and for animal manure as crop fertilizer In addition, manure returns organic matter to the soil, helping to maintain its structure as well as its water retention and drainage capacities

An integrated system of plant and animal production practices has a site-specific application that will, over the long term:

 satisfy human food and fiber needs

 enhance environmental quality and the natural resource base upon which the agricultural economy depends

 make the most efficient use of nonrenewable resources and on-farm resources and integrate, where appropriate, natural biological cycles and controls

 sustain the economic viability of farm operations

 enhance the quality of life for farmers and society as a whole

The integrated farming systems in Vietnam, like elsewhere, involve the combination of one or more types of domesticated animals with crops and fish in a manner such that, although each of these sub-systems may function independently, they are nevertheless complementary and their products are additive The output from one sub-system (e.g excreta) becomes the input to the others (e.g as feed for fish) This synergism and integration of the sub-systems thus produce a greater output than the sum of their individual effects These systems allow for minimizing waste through recycling, which in turn reduces the need for raw materials from outside, minimizing risks for farmers In addition to waste recycling the such integrated systems help to protect the environment and conserve biodiversity owing to using indigenous inputs, which also require less

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agro-chemicals Among the integrated crop-animal systems in Vietnam, the well-known VAC systems (Figure 1) can be herewith introduced as an example

Figure 1.1: The garden-pond-animal (VAC) systems

These systems have been known as the VAC systems, which integrate gardening (V), fish farming (A) and animal keeping (C) While gardening, fish farming and animal keeping provide main products for family consumption or for sale, by-products from one sub-system are used as inputs to the others, reducing the need for external chemicals and minimizing pollution

There are many other modifications of the above systems in different agro-ecological settings For example, in mountainous areas the VAC systems are combined with forestry (R) into so-called VACR systems (agro-forest systems) The VACR systems can provide complementary advantages of forage production, supply of fuel wood, improvement of soil fertility, maintenance

of permanent soil cover and thus environmental protection

More attention should be paid to developing farming systems that exploit the complementarity and synergism between plants and animals in resource-conserving systems

Review excercises

1 Define animals, livestock, animal science, animal husbandry, animal production

2 Develop a modest understanding of contributions of animals as consumables (food)

3 Give an overview of all the many nonfood uses of animals

excreta feed

excreta feed feed

water

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4 What are the roles of animals in traditional crop production?

5 What are the roles of animals for resource-poor farmers?

6 What can animal manure be used for?

7 What are the roles of animal production in food security?

8 Define and describe sustainable agriculture

9 Elaborate on the place of animals in sustainable agricultural systems

10 Elaborate on the roles of animals in the “VAC” systems in Vietnam

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Chapter 2

ANIMAL GENETICS AND BREEDING

Animal breeding is a traditional way of changing the performance of domestic animals through successive generations Farmers achieve this goal by selecting animals with outstanding performance in production traits, and using them as parents for the next generation Animal breeding as a science applies the principles of genetics and biometry to improve the efficiency of production in farm animals Animal breeding for genetic change plays a major role towards the increase in the range and efficiency of animal production Farm animals, particularly food animals, have been the subject of the most intensive breeding efforts This chapter outlines first the fundamental principles of genetics as basis for animal selection and breeding schemes that

follow

2.1 Fundamental principles of genetics

Genetics studies how living organisms inherit features from their ancestors Genetics tries to

identify which features are inherited, and work out the details of how these features are passed from generation to generation

Genetics may be conveniently divided into 3 areas of study: transmission genetics, molecular genetics and population genetics

2.1.1 Transmission Genetics

Transmission genetics is concerned with identifying the genes that affect a particular

characteristic, and also the patterns by which these genes are transmitted from generation to generation, or from cell to cell

The total genetic complement of a cell or organism is called a genome The particular version of

a genome carried by an individual is called the genotype, which is a set of genes A gene is defined as the smalest unit of inheritane Threfore, genes are the determiners of heridity

The outward manifestation of the expression of the genotype is called the phenotype Genes may express themselves in the phenotype in two general ways, known as additive and

nonaditive phenotypic expressions Individual genes can be identified through phenotypic inheritance patterns, but only if some variation is present in the phenotype Some phenotypic variation is discontinuous, e.g, yellow versus green pea seeds Discontinuous variation often can

be explained genetically by different forms of a gene called alleles: in an example from peas, Y

is the allele for the yellow phenotype, and y for green Plants and animals carry a pair of each

Transmission genetics has found widespread use in traditional agricultural practices, especially

in plant and animal breeding Many plants and animals used in commerce have been developed

by breeding procedures Furthermore, many diseases are known to be genetic in origin, resulting from a mutation to produce a disease-causing allele

2.1.2 Molecular Genetics

Molecular genetics focuses on the structure and function of the genetic units, ie, the chemical composition of genes and their expression in determining the structure of proteins, the most important functional components of cells

All animals (and plants as well) are made of small building blocks called cells The main parts of the cell include the nucleus and the cytoplasm The nucleus is the heart and brain of the cell and contains the chromosomes Each species of animals possesses a characteristic number of

chromosomes for that species (humans have 2 sets of 23 chromosomes, each parent contributing

a set, for a total of 46)

Genes, the determiners of heredity, are carried on

chromosomes Each chromosome contains a 50 mm

length of a threadlike chemical called DNA

(deoxyribonucleic acid); however, as each

chromosome is less than 0.005 mm long, the DNA

must be very efficiently packed through coiling and

supercoiling A gene is simply a functional segment

on the DNA thread It embodies a coded message, in

the form of a sequence of chemical units called

nucleotides

The sequence of most genes dictates the sequence of amino acids that make up a specific protein molecule Proteins are crucial in phenotypic expression because when you look at an organism what you see is either a protein or something that has been made by a protein Some proteins (called enzymes) control chemical reactions taking place in cells, and some are important structural components of cells, such as microtubules or muscle myofilaments

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DNA has the unique property of being able to make copies of itself (ie, replicate) That is, the gene as a portion of a DNA molecule has the ability to replicate itself when new cells are

formed Bacteria consist of single cells without a membrane-bound nucleus; each cell carries a

single circular DNA chromosome that replicates before the cell divides by binary fission, producing daughter cells that are an exact genetic copy of the original cell Plants, animals and fungy are composed of one or more cells having membrane-bound nuclei The body cells of plants and animals contain two sets of linear chromosomes per nucleus, and fungal cells one set per nucleus These chromosomes replicate before body cell division, and the chromosome copies are partitioned equally into daughter cells during an orderly nuclear division process called

mitosis

Animals also undergo a specialized nuclear division (meiosis) during the sexual cycle In animals, meiotic division results in sperms and eggs (or ovum), which contain only one chromosome set per cell When sperm and egg unite, the resulting cell (the zygote) is the

progenitor cell of the body of a new individual, and contains the usual two chromosome sets During meiosis different allele pairs can assort into new combinations, so zygotes are of many different genotypes, all differing from the two parents

Infrequently, DNA undergoes a sequence change, termed a mutation, that alters both genotype

and phenotype This is the ultimate source of all genetic variation Mutations without obvious cause are referred to as spontaneous mutations; induced mutations result mainly from damage to genes caused by environmental chemicals and radiation Mutations are the material on which the environment acts to result in evolution; thus, a mutation that gives an organism an advantage may permit it to produce more offspring which, in turn, contain the mutated gene Over time, an entire population may change

A revolution in molecular genetics occurred upon the invention of recombinant DNA technology This technology allowed genes to be isolated by cloning, characterized in detail by DNA sequencing, and manipulated experimentally in a test tube (in vitro mutagenesis) Improvements of recombinant DNA technology have led to the ability to characterize whole genomes Recombinant DNA technology also allows genes to be removed from their original organism and spliced into the chromosomes of other organisms, to create transgenic organisms

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Weinberg formula, which states that under conditions of random mating and with no change of allele frequency, the structure of a very large population can be described as p2 of genotype AA, 2pq of Aa and q2 of aa, where p and q are the frequencies (proportions) of alleles A and a in that population This will give a stable population structure The Hardy-Weinberg proportions can be changed by mutation, selection, random changes in allele frequency (genetic drift), and migration, all of which can be considered to be evolutionary forces

In other words, population genetics is the study of the allele frequency distribution and change

under the influence of the four evolutionary processes: natural selection, genetic drift, mutation and gene flow It also takes account of population subdivision and population structure in space

As such, it attempts to explain such phenomena as adaptation and speciation Population genetics was a vital ingredient in the modern evolutionary synthesis, its primary founders were Sewall Wright, J B S Haldane and R A Fisher, who also laid the foundations for the related discipline

of quantitative genetics

Quantitative genetics is the study of continuous traits (such as height or weight) and its

underlying mechanisms It is effectively an extension of simple Mendelian inheritance in that the combined effect of the many underlying genes results in a continuous distribution of phenotypic values

The phenotypic value (P) of an individual is the combined effect of the genotypic value (G) and the environmental deviation (E):

P = G + E The genotypic value is the combined effect of all the genetic effects, including nuclear genes, mitochondrial genes and interactions between the genes It is therefore often subdivided in an additive (A) and a dominance component (D) The additive effect described the cumulative effect of the individual genes, while the dominance effect is the result of interactions between those genes The environmental deviation can be subdivided in a pure environmental component (E) and an interaction factor (I) describing the interaction between genes and the environment This can be described as:

P = A + D + E + I The contribution of those components cannot be determined in a single individual, but they can

be estimated for whole populations by estimating the variances for those components, denoted as:

VP = VA + VD + VE + VI

The heritability of a trait is the proportion of the total (i.e phenotypic) variation (VP) that is

explained by the genetic variation This is the total genetic variation (VG) in broad sense heritabilities (H2), while only the additive genetic variation (VA) is used for narrow sense

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heritabilities (h2), often simply called heritability The latter gives an indication how a trait will respond to natural or artificial selection

2.2 Animal selection

2.2.1 Purpose of animal selection

The purpose of animal selection is to identify and select superior breeding ainimals which possess a large proportion of superior genes for a desirable trait, or traits

2.2.2 Methods of animal selection

Methods of selection are within and between family selection, individual or mass selection, sibling selection, and progeny testing, with many variations

 Within family selection uses the best individual from each family for breeding

 Between family selection uses the whole family for selection

 Mass selection uses records of only the candidates for selection Mass selection is most

effective when heritability is high and the trait is expressed early in life, in which case all that is required is observation and selection based on phenotypes

When mass selection is not appropriate, other methods of selection, which make use of relatives

or progeny, can be used singularly or in combination

 Modern selection technologies allow use of all these types of selection at the same time,

which results in greater accuracy

2.3 Breeding schemes

Once superior animals are identified and selected as breeding stock, which is a group of animals used for purpose of planned breeding, it is necessary to devise breeding schemes (mating systems) which will give the most genetic improvement The different breeding schemes may be grouped into purebreeding and crossbreeding

2.3.1 Purebreeding

Purebreeding is the mating of males and females of the same breed Purebred breeding aims to establish and maintain stable traits, that animals will pass to the next generation By "breeding the best to the best," employing a certain degree of inbreeding, considerable culling, and selection for "superior" qualities, one could develop a bloodline or "breed" superior in certain respects to the original base stock Such animals can be recorded with a breed registry, the organisation that maintains pedigrees and/or stud books The goal of purebreeding should be to

Inbreeding is generally detrimental in domestic animals Inbreeding depression is reduced

fitness in a given population as a result of inbreeding Increased inbreeding is accompanied by reduced fertility, slower growth rates, greater susceptibility to disease, and higher mortality rates

As a result, producers try to avoid mating related animals This is not always possible, though, when long-continued selection for the same traits is practiced within a small population, because parents of future generations are the best candidates from the last generation, and some inbreeding tends to accumulate The rate of inbreeding can be reduced, but, if inbreeding depression becomes evident, some method of introducing more diverse genes will be needed The most common method is some form of crossbreeding

Linebreeding

Line breeding is the most conservative form of inbreeding, is usually associated with slower improvement and limited risk of producing undesirable individuals It can involve matings between closely or distantly related animals, but it does not emphasize continuous sire-daughter, dam-son, or brother-sister matings

The main purpose of linebreeding is to transmit a large percentage of one outstanding ancestor's genes from generation to generation without causing an increase in the frequency of undesirable traits often associated with inbreeding

Because linebreeding is not based strictly on mating closely related individuals (with very similar gene types), it does not necessarily cause a rapid increase in homozygous gene pairs Consequently, it will not expose undesirable recessive genes as extensively as closebreeding For this reason, linebreeding is generally a safer inbreeding program for most breeders

Intensive inbreeding (and resulting increased homozygosity) is often directly related to an increase in the expression of many undesirable traits Therefore, the linebreeder should carefully

21

study pedigrees for each prospective mating and determine if, and how closely, the male and female are related By following certain guidelines, the breeder can limit inbreeding (and, therefore, homozygosity) within their herd At the same time, they may increase the influence of

a common ancestor upon the entire strain or family

Outbreeding/Outcrossing

Outbreeding or outcrossing is the mating of males and females from unrelated families in the same breed Outcrossing is the practice of introducing unrelated genetic material into a breeding

line It increases genetic diversity, thus reducing the probability of all individuals being subject

to disease or reducing genetic abnormalities (only within the first generation)

It is used in line-breeding to restore vigor or size and fertility to a breeding line "Line-breeding",

is where animals carry a common ancestor in their pedigrees and are bred together, should be considered distinct from the term "in-breeding" which is the production of offspring by parents more closely related than the average

2.3.2 Crossbreeding

Crossbreeding involves the mating of animals from different breeds Crossbreeding offers two

primary advantages: the opportunity for breed complementarity and heterosis (also called

hybrid vigor) Normally, breeds are chosen that have complementary traits that will enhance the offsprings’ economic value An example is the crossbreeding of Yorkshire and Duroc breeds of pigs Yorkshires have acceptable rates of gain in muscle mass and produce large litters, and Durocs are very muscular and have other acceptable traits, so these breeds are complementary Another example is Angus and Charolais beef cattle Angus produce high-quality beef and Charolais are especially large, so crossbreeding produces an animal with acceptable quality and size

The other consideration in crossbreeding is heterosis, or hybrid vigour, which is displayed when the offspring performance exceeds the average performance of the parent breeds This is a common phenomenon in which increased size, growth rate, and fertility are displayed by crossbred offspring, especially when the breeds are more genetically dissimilar Such increases generally do not increase in successive generations of crossbred stock, so purebred lines must be retained for crossbreeding and for continual improvement in the parent breeds In general, there

is more heterosis for traits with low heritability In particular, heterosis is thought to be associated with the collective action of many genes having small effects individually but large effects cumulatively Because of hybrid vigour, a high proportion of commercial pork and beef come from crossbred animals

There are unlimitted crossbreeding schemes The most commonly utilized crossbreeding schemes include:

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 two-breed cross

 two-breed rotational cross

 three-breed rotational cross

 static terminal sire

 rotational terminal sire

These schems are listed in order from least to most demanding in terms of facilities and labor The same ranking applies to the realized benefits; the two-breed cross is the easiest to manage but results in the least heterosis and little opportunity for breed complementarity Use of artificial insemination (A.I.) or multiple breeding pastures is required for use of complex systems Following is a brief description of each system for cattle crossbreeding:

Two-Breed Cross

Use of a two-breed cross involves maintaining purebred/straightbred cows of a single breed and mating all females to a bull of another breed This is a simple system that requires only one breeding pasture, but realizes less than half of the possible heterosis Use of a two-breed cross allows realization of direct heterosis (advantages of a crossbred calf), but not maternal heterosis (advantages of a crossbred cow) All other systems result in both direct and maternal heterosis A further drawback is that straightbred females must be purchased as replacements to continue the breeding program A possible use of this system is for generation of F1 (purebred x purebred) replacements for sale to producers who are using more complex systems This would be a means for owners of small cowherds to "add value" to their cattle

Two-Breed Rotational Cross

In this scheme, bulls of two breeds are used Females sired by a bull of a particular breed are mated to a bull of the other breed Thus, after several generations, approximately two-thirds of the genetics of each calf result from breed it was sired by, one-third from the other breed The two breeds will be equally represented within the cowherd if the number of each breed culled each year is equal If natural service is used, this system requires at least two breeding pastures and requires that both breeds used be approximately equal in terms of size, nutritional requirements and maternal potential

Three-Breed Rotational Cross

Nearly all of the possible heterosis is realized with proper management of a three-breed rotational crossbreeding system This system is similar to the two-breed rotational cross except that three breeds are used As in the two-breed rotational cross, females are mated to a bull of the breed that is least related to them (the sire breed of their maternal grandam) Benefits include a high degree of heterosis and potential for outstanding breed complementarity However, this

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system is more difficult to maintain than the two previously described and at least three breeding pastures are required if A.I is not used In herds of less than 100 cows, the cost to maintain adequate bull power in each of three breeds may be prohibitive Furthermore, inclusion of three breeds may make it difficult to maintain a uniform cowherd

Static Terminal Sire

In this scheme the cowherd consists entirely of F1 females that are mated to bulls of a third, terminal sire breed All calves are marketed Only one breeding pasture is required and heterosis and breed complementarity can be nearly maximized However, F1 replacement females must be purchased Locating a steady supply of economical, high-quality replacements can be difficult in most areas

Rotational Terminal Sire

This scheme, which is used in many swine herds, is similar to the static terminal sire system except that a portion of the herd (typically 20 to 30 percent) is designated for production of replacement females These females are maintained separately from the rest of the herd and mated to bulls of a maternal breed, possibly in a two-breed rotational system The majority of the cows in the herd are mated to a terminal sire and all calves marketed This can be a demanding scheme to maintain but will produce excellent results

A more feasible variant may be to mate all heifers to maternal breed bulls and keep replacements from them while the mature cowherd produces only terminal-sired calves The logic behind this

is that heifers should be managed separately from mature cows anyway and that most (but by no means all) maternal breed bulls are easier calving than terminal breed bulls This may make A.I

of heifers to high-quality maternal bulls a practical way to upgrade the maternal performance of the herd over time

Review excercises

1 What is genetics and its areas of study?

2 Elaborate on transmission genetics

3 Elaborate on molecular genetics

4 Elaborate on population and quantitative genetics

5 How does animal breeding utilise trait variations?

6 What are the purpose and methods of animal selection?

7 Describe the role and different methods of animal selection

8 What is purebreeding? Describe its different breeding schemes

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9 What is crossbreeding? Describe its different breeding schemes

10 Determine what breeding schemes the two following figures represent?

3.1 Reproductivion in mammalian animals

3.1.1 The reproductive systems

a The female reproductive system

The female reproductive system contains two main divisions: the vagina and uterus, which act as the receptacle for the male's sperm, and the ovaries, which produce the female's ova All of these parts are always internal The vagina is attached to the uterus through the cervix, while the uterus

is attached to the ovaries via the Fallopian tubes At certain intervals, the ovaries release an ovum (the singular of ova), which passes through the Fallopian tube into the uterus

If, in this transit, it meets with sperm, the

sperm penetrate and merge with the egg,

fertilizing it The fertilization usually occurs in

the oviducts, but can happen in the uterus

itself The zygote then implants itself in the

wall of the uterus, where it begins the

processes of embryogenesis and

morphogenesis When developed enough to

survive outside the womb, the cervix dilates

and contractions of the uterus propel the fetus

through the birth canal, which is the vagina

The ova are larger than sperm and are

generally all created by birth They are for the

most part stationary, aside from their transit to

the uterus, and contain nutrients for the later

zygote and embryo Over a regular interval, a process of oogenesis matures one ovum to be sent

Figure 3.1 The female reproductive system

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down the Fallopian tube attached to its ovary in anticipation of fertilization If not fertilized, this egg is flushed out of the system through menstruation in humans and great apes and reabsorbed

in all other mammals in the estrus cycle

b The male reproductive system

The male reproductive system contains two main divisions: the penis, and the testicles, the latter

of which is where sperm are produced In humans, both of these organs are outside the

abdominal cavity, but they can be primarily housed within the abdomen in other animals (for

instance, in dogs, the penis is internal except when mating) Having the testicles outside the abdomen best facilitates temperature regulation of the sperm, which require specific

temperatures to survive Sperm are the smaller of the two gametes and are generally very

short-lived, requiring males to produce them continuously from the time of sexual maturity until death Prior to ejaculation the produced sperm are stored in the seminal vesicle, a small gland

A sperm cell is motile and swims via chemotaxis, using its flagellum to propel itself towards the

ovum

A sperm, from the ancient Greek word

σπέρμα (seed) and ζῷον (living being) and

more commonly known as a sperm cell, is

the haploid cell that is the male gamete It

joins an ovum to form a zygote A zygote is

a single cell, with a complete set of

chromosomes, that normally develops into

an embryo Sperm cells contribute half of the

genetic information to the diploid offspring

In mammals, the sex of the offspring is

determined by the sperm cell: a

spermatozoon bearing a Y chromosome will

lead to a male (XY) offspring, while one

bearing an X chromosome will lead to a

female (XX) offspring (the ovum always

provides an X chromosome)

3.1.2 Reproductive processes

a Puberty

Puberty is the time in an animal's life cycle when the animal reaches a developmental state in

which it is capable of reproducing By defination, it is the time in adolescence when male and

Figure 3.2 The male reproductive system

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female gonads are capable of releasing gamates This happens several weeks before sexual maturity; the first gamates are usually incapable of fertilization A number of factors influence the age at which an animal reaches puberty Among the factors are: animal species, breed, climate, season, nutrition, sex, management system, and stress

In a production system that relies on reproduction to be profitable, the sooner an animal reaches puberty, the sooner the manager will be able to realize a profit from the animal Once animals reach puberty, we tend to concentrate our attention on the female, since she is producing the desired product It is not necessary to keep as many males as females for breeding purposes, and when artificial insemination (AI) is used, there may be no intact male animals in a livestock production system However, until or unless cloning of animals from somatic cells becomes economically feasible and socially acceptable the male will continue to play an important role in reproduction

b The estrous cycle

The estrous cycle (also oestrous cycle) is the cycle in the female reproductive system that prepares it for reproduction The estrous cycle comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females Estrous cycles start after puberty in sexually mature females and are interrupted by anestrous phases or pregnancies The length of the estrous cycle varies with species (Table 3.1) and can be divided into 4 phases: estrus, metestrus, diestrus and proestrus Because females can only become pregnant and produce offspring during a short interval within the estrous cycle, it is very important to understand the cycle and be able to identify animals at critical stages of the cycle

Proestrus

One or several follicles of the ovary are starting to grow Their number is specific for the species Typically this phase can last as little as one day or as long as 3 weeks, depending on the species Under the influence of estrogen the lining in the uterus (endometrium) starts to develop Some animals may experience vaginal secretions that could be bloody The female is not yet sexually receptive

Estrus

Estrus refers to the phase when the female is sexually receptive ("in heat," or "on heat" in

British English) Under regulation by gonadotropic hormones, ovarian follicles are maturing and estrogen secretions exert their biggest influence The animal exhibits a sexually receptive behavior, a situation that may be signaled by visible physiologic changes A signal trait of estrus

is the lordosis reflex, in which the animal spontaneously elevates her hindquarters

In some species, the vulvae are reddened Ovulation may occur spontaneously in some species (e.g cow), while in others it is induced by copulation (e.g cat) If there is no copulation in an

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induced ovulator, estrus may continue for many days, followed by 'interestrus,' and the estrus

phase starts again until copulation and ovulation occur

Metestrus

During this phase, the signs of estrogen stimulation subside and the corpus luteum starts to form The uterine lining begins to secrete small amounts of progesterone This phase typically is brief and may last 1 to 5 days In some animals bleeding may be noted due to declining estrogen levels

Diestrus

Diestrus is characterised by the activity of the corpus luteum that produces progesterone In the absence of pregnancy the diestrus phase (also termed pseudo-pregnancy) terminates with the regression of the corpus luteum The lining in the uterus is not shed, but will be reorganised for the next cycle

Table 3.1 Puberty on set and estrous cycle in some farm animals

Species Puberty onset Estrous cycle

Ave Age Age Range Ave Length Range Estrus Duration

Cow 12 months 4-18 months 21 days 18-24 days 18 hours

Mare 12 months 10-24 months 21 days 19-26 days 6 days

Ewe 9 months 5-12 months 16.5 days 14-20 days 30 hours

Sow 7 months 4-9 months 21 days 18-24 days 2-3 days

Heat detection is an important livestock management tool as missed heats (estrous cycles in

which an animal remains "open" or is not bred) result in:

 Increased parturition intervals, decreased numbers of offspring produced per year or lifespan of the female;

 Longer dry periods and consequently decreased milk production per year or lifespan of a diary cow;

 Less use and reduced efficiency of facilities

(milking parlors, farrowing barns, calving and lambing

sheds, etc.);

 Reduced profits due to the costs of upkeep for

animals that are not producing at their optimal efficiency

Detecting estrus is a challenge to all livestock production

systems relying upon reproduction for their survival

Some livestock systems keep intact male animals and

intermingle them with the females, letting the males do

the job of heat detection However, if hand breeding or Figure 3.3 Heat detection

in the estrus phase of the estrous cycle

Currently, the best means of heat detection is observation of the animals

o Observation should be done during the animals' normal activities;

o Observation is usually done during morning hours, when the animals are normally more active (With cattle, observation must be done twice daily, or estrus may be missed due to the short 18 hour length of estrus);

o Recording of dates and times of estrus activity will allow the herdsperson to carefully observe the animal at the anticipated time of estrus in the next cycle;

o Recording of the time of certain events such as weaning, will allow the herdsperson to carefully observe groups of animals in which estrus would be expected within a few days For example, animals that are suckling offspring will often exhibit anestrus (no cyclic activity) until the offspring are weaned At that time the animal will rapidly enter proestrus and will exhibit signs of estrus within a few days

The primary sign of estrus is the female animal standing to be mounted This is the most

important and most reliable sign of estrus and receptivity for breeding to establish pregnancy Some animals, however will not exhibit this primary sign and the herdsperson will

have to rely on secondary signs of estrus to determine when to breed the female A number of

other devices, however, are available to aid the farm manager in this task

c Fertilization

Fertilisation (also known as conception, fecundation and

syngamy), is the fusion of gametes to produce a new

organism In animals, the process involves a sperm fusing

with an ovum, which eventually leads to the development

of an embryo Depending on the animal species, the

process can occur within the body of the female in

internal fertilisation, or outside in the case of external

fertilisation

d Pregancy

Pregnancy is that period of time from the successful breeding of an animal with fertilization of

the ovum, until offspring are born from that breeding This is often referred to as the "gestation"

of the animal During this period of time the fetus develops, dividing via mitosis inside the

Figure 3.4 Fertilisation

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female The fetus receives all of its nutrition and

oxygenated blood from the female, filtered through

the placenta, which is attached to the fetus' abdomen

via an umbilical cord This drain of nutrients can be

quite taxing on the female, who is required to ingest

slightly higher levels of calories In addition, certain

vitamins and other nutrients are required in greater

quantities than normal, often creating abnormal eating

habits

The length of gestation, called the gestation period, varies greatly from species to species:

 Cow = 283 days; approximately 9 months

 Ewe = 148 days; approximately 5 months

 Sow = 114 days; approximately 4 months

 Mare = 336 days; approximately 11 months

In animal management systems where reproduction is important to profitibility, it is important to shorten the interval between each pregnancy as much as possible As a consequence, estrus or

heat detection is important to identify animals eligible for breeding and pregnancy testing is

advisable to make sure that breeding resulted in pregnancy If breeding did not result in pregnancy, it is important to identify the lack of pregnancy at the earliest possible time to decrease the amount of time the dam is "open" The profitablity of a herd will decrease with an increase in the number of days open for the brood herd There are a number of ways in which to determine whether an animal is pregnant or not The three most commonly used methods are: rectal palpation, ultrasound, and hormone measurements

e Parturition

Parturition is the act or process of giving birth to offspring The terms used to describe parturition vary with the species of animal it is being used to describe The following are examples of parturition terminology:

A dog whelps and gives birth to puppies

A cow calves and give birth to a calf

A sow farrows and gives birth to piglets

A ewe lambs and give birth to lambs

A horse foals and give birth to a foal

Once the fetus is sufficiently developed, a number of

physical, physiological and hormonal changes take

place to prepare the dam and fetus for parturition,

which begins with contractions of the uterus and the

Figure 3.5 The female reproductive

system

Figure 3.6 Parturition

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dilation of the cervix The fetus then descends to the cervix, where it is pushed out into the vagina, and eventually out of the female The newborn should typically begin respiration on its own shortly after birth Not long after, the placenta is passed as well Most mammals eat this, as

it is a good source of protein and other vital nutrients needed for caring for the young The end of the umbilical cord attached to the young’s abdomen eventually falls off on its own.

3.2 Reproduction in poultry

So far, we have examined reproduction in mammalian species in which the offspring develop inside the body of the dam and, after birth, are provided nourishment in the form of milk produced by the dam In the avian species, however, the dam produces an egg in which, if

fertilized, the offspring will undergo growth and development outside the body of the dam The

dam does not suckle it's young, either As a consequence, there are a number of contrasts between avian and mammalian reproductive life cycles

3.2.1 The reproductive system

The reproductive tract of the hen is also different from mammals, and different functions are performed in different segments of the tract The major structures are as follows:

 Ovary - containing immature and

mature follicles The mature follicles

consist of the egg "yolk" and the

unfertilized ovum

 Infundibulum - yolk with

attached ovum is snatched up by the

infundibulum It is at this point in the

reproductive tract that the ovum is

fertilized if the hen has been mated with a

cockerel Spermatozoa from the cockerel

are stored in "sperm nests" located within

the infundibulum and are capable of

fertilizing ova for up to 30 days after

mating

 Magnum - while traveling

through this part of the oviduct, the

albumin or egg white is formed

 Isthmus - the tough outer

membrane located just beneath the egg

shell is formed in this part of the oviduct

 Uterus - also referred to as the

"shell gland", this is where the egg shell Figure 3.7 The reproductive systems of the hen

32

is formed Most of the transit time from ovulation until the egg is laid is spent in the uterus

 Vagina - the egg travels through the vagina into the cloaca, from which it is "laid."

 Cloaca - this is the common external opening from which the contents of the urinary tract (urates), the intestinal tract (feces) and the reproductive tract (eggs) exit the hen

3.2.2 Puberty

The hen reaches puberty and starts to produce eggs at 4-5 months of age As with mammals, the

reproductive system is not functioning completely normally at the onset and hens at puberty produce small egg sizes and high percentages of eggs with twin yolks Since these eggs do not produce viable offspring, hens are not bred to produce young until they reach 5-6 months of age

The cockerel is capable of insemination at 4-5 months of age, but, like the hen, is not used for

breeding until 6 months of age to insure viable sperm

3.2.3 Breeding

The natural instinct of the hen is to lay a "clutch" of eggs, become "broody", stop laying eggs (ovulating), and set on eggs to hatch This broodiness has, for the most part, been bred out of our commercial breeds of poultry, and hens will produce eggs continuously Hens do not have an estrus cycle, and will lay an egg nearly every day

In contrast with mammalian species in which both ovaries are functional and either ovulate simultaneously, or alternately, 99% of hens have only one functional ovary

General information on reproduction of the hen is as follows:

 A hen is capable of producing an egg every 25 hours

 Eggs are produced and laid regardless of whether the hen has been mated and the eggs are fertile or not

 A hen is capable of laying approximately 270 eggs per year

 The embryo in a cracked fertile egg will not develop

 Incubation and hatching of fertile eggs:

o humidity & temperature control are important factors in the hatchability of

an immunity (this is similar to colostrum in mammals)

 The chick develops outside and independent of the hen, and does not need the hen for survival provided that the proper environment is provided by man for incubation of the egg Mammals develop inside the uterus of the dam and are dependent upon the health and well-being of the dam throughout the entire gestation for their health and well-being

3.4 Reproductive technology

3.4.1 Artificial insemination (AI)

Artificial insemination (AI) is the process by which

sperm is placed into the reproductive tract of a female

for the purpose of impregnating the female by using

means other than sexual intercourse Specifically,

freshly ejaculated sperm, or sperm which has been

frozen and thawed, is placed in the cervix

(intracervical insemination) (ICI)) or in the female's

uterus (intrauterine insemination) (IUI) by artificial

means In the actual procedure which has become

widely used in animal breeding nowadays, semen is

obtained from a male animal and, after being diluted,

is deep-frozen, after which it can be stored for long periods of time without losing its fertility

For use, the semen is thawed and then introduced into the genital tract of a female animal in heat

The practical use of artificial insemination in animals was developed during the early 1900s in Russia and spread to other countries in the 1930s Its chief advantage is that the desirable characteristics of a bull or other male livestock animal can be passed on more quickly and to more progeny than if that animal were mated with females in a natural fashion Ten thousand or more calves have been produced annually from a single bull through the use of artificial

Figure 3.7 Artificial insemination

34

insemination Through use of AI, new genetics can be introduced into the herd or flock without running the risk of inroducing disease agents that may be carried by an apparently healthy animal

3.3.2 Embryo transfer (ET)

Embryo transfer (ET) refers to a technology

whereby one or several embryos are placed into

the uterus of the female with the intent to

establish a pregnancy The practice of embryo

transfer is an ever changing science that involves

three major events It begins with selection,

superovulation, and artificial insemination (AI) of

the donor animal Next, the embryos are

recovered from the donor through either surgical

or nonsurgical means, evaluated, and then frozen

or transferred fresh Lastly, the recipient animals

are synchronized to be in the same stage of the

estrous cycle as the donor when the embryo was

recovered and receive the embryos through

surgical or nonsurgical techniques

There are many reasons a producer might select

embryo transfer for his/her particular operation

The first reason would probably be the potential

for genetic improvement in the herd Through

artificial insemination, superior male genetics can

be spread across a herd; with embryo transfer,

superior female genetics can also be spread across

a specific herd or even many herds

Superovulation and embryo transfer allows one particular female to produce many offspring in a given year and many more over her reproductive lifetime Each of these offspring would potentially carry the superior traits of the mother, such as increased weight gain, improved carcass merit, or even increased milk production The transfer of embryos provides the opportunity to introduce genetic material into populations of livestock while greatly reducing the risk for transmission of infectious diseases Embryo transfer may also eliminate the stress of parturition on a desirable animal, thereby increasing her reproductive life span ET allows the continued use of animals such as competition mares to continue training and showing, while

Figure 3.8 Embryo transfer

35

producing foals Salvage of reproductive function and potential twinning are a few of the other benefits of embryo transfer Finally, the impact embryo transfer has had and will have on the research environment cannot be overlooked Techniques such as gene insertion, embryo splitting, embryo sexing, and pronuclear DNA injections would not be as feasible without embryo transfer technology

Review excercises

1 Describe the female reproductive systems of mammalian animals

2 Describe the male reproductive systems of mammalian animals

3 Describe the reproductive system of the hen

4 What is the estrous cycle? Describe the different phases of the cycle

5 Why is heat detection an important and what is the best way to detect an animal on heat?

6 Describe the processes of fertilization, gestation and birth in farm animals

7 Describe the main features of puberty and breeding of the hen

8 What are the main differences in reproduction between mammalian animals and poultry?

9 Outline the purpose and steps of artifition insemination

10 What are the purposes and main steps of embryo transfer in farm animals?

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Chapter 4

ANIMAL NUTRITION AND FEEDING

Nutrition contributes to wellness and productivity of animals Poor nutrition results in poor reproduction, poor growth, poor productivity, and higher feed costs Poor nutrition can have injurious impacts on health, while many common health problems can be prevented or alleviated with good nutrition Animal nutrition as a science is the study of feed, including how feed nourishes animal bodies and how feed influences animal health The objective of this chpater is

to establish a common understanding of some nutrition basics and an appreciation for proper livestock nutrition

4.1 Nutrients and their functions

A nutrient is defined as "any feed constituent or group of feed constituents of the same general chemical composition that aids in support of animal life" Animals need a variety of nutrients

to meet their basic needs They are used to build and repair tissues, regulate body processes and

are converted to and used as energy Animals must have nutrients in each of six major classes: water, protein, carbohydrates, fats, vitamins, and minerals Organic nutrients include carbohydrates, fats, proteins (or their building blocks, amino acids), and vitamins Inorganic chemical compounds such as dietary minerals, water, and oxygen may also be considered nutrients A nutrient is said to be "essential" if it must be obtained from an external source, either because the organism cannot synthesize it or produces insufficient quantities Nutrients needed in larger quantities are called macronutrients and those that are needed in very small amounts are micronutrients The macronutrients are carbohydrates, fats, fiber, proteins, and water The micronutrients are minerals and vitamins The effects of nutrients are dose-dependent and shortages are called deficiencies

4.1.1 Water

This nutrient provides the basis for all the fluid of the animal’s body The blood stream must be a liquid in order for circulation to occur Digestion requires moisture for the breakdown of the nutrients and the movement of the feed through the digestive tract Water is needed to produce milk It is needed to provide fluid for the manufacture of all the bodily fluids It provides the cells with pressure that allows them to maintain their shape It helps the body maintain a constant temperature Another vital function of water is that of flushing the animal’s body of wastes and

Since water is essential for sustaining life, animals must have frequent intakes of water to remain alive Animals generally need about 3 pounds of water for every pound of solid feed they consume Some of this water comes in the feed itself For instance, animals that graze obtain water from the succulent green forages they eat Some water can be obtained in feeds such as silage that have relatively high water content However, most of the water an animal needs comes from the water it drinks Since water is so essential, producers make sure that animals are given a constant supply of clean water

4.1.2 Protein

Proteins are composed of compounds known as amino acids Amino acids are often said to

be the building blocks of life because they go into the formation of tissues that provide growth for the animal Muscle production in particular is dependent on the amino acids found in protein

To a certain degree, protein is also used to provide energy

Like water, some animals need larger amounts of protein than others Young, rapidly growing animals need more protein than mature animals This is because the amino acids in the protein are needed to build muscle, skin, hair, bones, and all of the other cells that go into the growth process A cow that is giving large amounts of milk needs more protein than an animal that is not lactating

In all, there are over 20 different types of amino acids that an animal’s body uses Of these, there are 10 essential amino acids that the animal must obtain from its feed The other amino acids can

be synthesized by the animal’s digestive tract This means that the 13 nonessential; amino acids can be made from the 10 that the animal consumes In this sense, the 10 are essential in that they cannot be manufactured by the animal and must be consumed from feed

Protein can come from basically two sources: animal and plant Carnivores (animals that eat other animals), such as dogs, cats, and foxes, get almost all of their protein from meat After all, the muscles in an animal’s body are primarily composed of protein and can serve as feed for another anima Omnivores (an animal that eats both plants and animals), such as human and pigs, can get protein from both plants and animals Animals that eat only plants are called herbivores, and they must get protein exclusively from plants

38

Most feedstuffs that are rich in protein come from plant sources Much of plant protein that goes into the feed of animals comes from the vegetable oil industry Cooking oil is usually pressed from cottonseed, soybeans, peanuts, or corn These seeds are run through huge presses where the oil is squeezed out The material that is left is in the form of a cake composed of the seas minus the oil It is dried and ground into meals for feed This material is usually 40-50 percent crude protein and can greatly increase the percentage of protein in a feed This feedstuff is the mixed with the other feedstuffs in the proper ratio to give the desired protein content for the feed Animals may not be able to digest all the protein in a particular feed The total amount of protein

in a feed is called the crude protein content Digestible protein is the protein in a feed that can be digested and used by the animal The digestible is usually about 50-80 percent of the crude protein

4.1.3 Carbohydrates

Carbohydrates are compounds made up of carbon, hydrogen, and oxygen (CHO) They include sugars, starch, and cellulose, and are the major organic compounds in plant Almost all carbohydrates come from plants and are developed by photosynthesis The main source of energy for animals comes from carbohydrates

Starch is generally found in grain It is used by the plant as energy storage for the seed Grains such as wheat and corn contain a lot of starch and therefore a lot of energy for the animal to use Feeds that are high in grain content are known as concentrates because of the high concentration

of carbohydrates Starches are composed of sugars, and as digestion occurs, the starch is broken down into the component sugars

There are several different types of sugars Two broad groups are monosaccharide (the simple sugars) and disaccharides (the more complex sugars) Simple or complex refers to the chemical composition of the sugar and the different ways the molecules are formed There are several common simple sugars (monosaccharide); among these are glucose, fructose, and galactose Glucose is the simplest of all the sugars and is found in a low concentration in plant material’s blood The animal’s body breaks down some of the other sugar into glucose Fructose is found in fruits and honey and is the sweetest of all the sugars Common table sugar (sucrose) is a disaccharide composed of fructose and glucose Galactose is obtained from the breakdown of the disaccharide lactose (milk sugar)

Cellulose is the portion of cell walls that gives the plant its rigid structure The enzymes in an animal’s digestive system can’t break down cellulose However, some animals have microorganisms in their digestive system that break down the cellulose fiber so the enzymes can digest the material

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4.1.4 Fats

Fats are part of a group of organic compounds known as lipids These compounds will not dissolve in water but will dissolve in certain organic solvents Besides fats and oils, lipids also include cholesterol Fats are found in both plants and animals They serve as concentrated storage places for energy Oil within seeds such as peanuts and soybeans is an example of plant fats

Fats serve the purpose of providing energy for the animal and of storing excess energy When an animal consumes more energy (especially in the form of fats) than it needs to provide for all the needed bodily functions, the excess is stored in the form of fat When the body does not take enough energy to perform the normal bodily functions, these reserves of fat are used

Certain acids, referred to as the essential fatty acids, are also derived from fats These acids are necessary in some animals for the production of some hormones and hormone like substances The most important sources of fats in feed for agricultural animals are the grains that contain oil Corn and most other feed grains contain oil that is used as a fat source by the animal Some types

of animals, pig for example, may have problem if fed too much oil Hogs fatted on oily feeds such as whole peanuts may produce soft, oily pork that is not acceptable to the consumers

4.1.5 Minerals

Minerals are the only group of nutrients besides water that are inorganic Animals must have a sufficient intake of these inorganic materials to provide the building materials for their body structure Bones are formed by a combination of calcium and phosphorus In addition to building bones, minerals provide other essential needs They aid in the construction of muscles, blood cells, internal organs, and enzymes Animals with a deficiency in minerals never develop properly and are more susceptible to diseases

The mineral elements required by animals include seven macrominerals (required in relatively large amounts in the diet) and nine microminerals of trace minerals (required in very small amounts in the diet) The macrominerals are calcium, phosphorus, sodium, chlorine, magnesium, potasium, and sulphur The microminerals are cobalt, copper, fluorine, iron iodine, manganese, molybdenum, selenium, and zinc

Minerals are usually added to the feed of animals in their chemical form Calcium is sometimes added from other animal sources For example, ground up oyster shells and eggshells are fed to laying hens to provide materials for their bodies to create strong eggshells

Minerals are often fed free choice This means that the animals are given free access to the minerals and are allowed to eat all they wish For cattle, this is done by a mineral box or trough,

or by the use of a salt block Essential minerals are in the block, and the animals get them as the lick or the block for salt