AGE 306 — Introduction to Animal Breeding: Lecture Note

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AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: AGE 306 Course title: Introduction to Animal Breeding Course credit load: 2 Units Series 1: Basic Concepts of Animal Breeding • Part 1.1: Definition, Scope, and Importance of Animal Breeding o Sub Part 1.1.1: Definition and scope of animal breeding o Sub Part 1.1.2: Historical development of animal breeding o Sub Part 1.1.3: Importance of animal breeding in livestock production • Part 1.2: Key Concepts in Animal Breeding o Sub Part 1.2.1: Genotype, phenotype, and the environment o Sub Part 1.2.2: Heritability and its significance o Sub Part 1.2.3: Genetic and phenotypic variation in livestock • Part 1.3: Goals and Criteria of Animal Breeding o Sub Part 1.3.1: Breeding objectives and economic traits o Sub Part 1.3.2: Selection and the breeding cycle o Sub Part 1.3.3: Genetic gain and factors affecting it • Part 1.4: Overview of Livestock Species and Their Breeding Priorities o Sub Part 1.4.1: Cattle breeding priorities in Nigeria o Sub Part 1.4.2: Small ruminant and pig breeding priorities o Sub Part 1.4.3: Poultry breeding priorities and commercial application

AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Introduction Animal breeding is the applied science concerned with improving the genetic merit of livestock populations for traits of economic importance. It draws on the principles of genetics, statistics, and reproductive biology to design programmes that increase animal productivity, efficiency, and adaptability over successive generations. The practice of animal breeding is as old as domestication itself, but the scientific foundation that underpins modern breeding has developed rapidly over the past century. This Series introduces you to the foundational concepts of animal breeding. We begin by defining the discipline and tracing its historical development, then examine the key concepts of genotype, phenotype, heritability, and variation that underpin all breeding decisions. We proceed to the goals of breeding programmes, including the definition of breeding objectives and the calculation of genetic gain. The Series concludes by surveying the breeding priorities for cattle, small ruminants, pigs, and poultry in the Nigerian context. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define animal breeding and describe its scope and importance in livestock production (Linked to Part 1.1), • SLO 1.2 outline the historical development of animal breeding from traditional selection to modern genomics (Linked to Part 1.1), • SLO 1.3 distinguish between genotype, phenotype, and environmental effects on livestock performance (Linked to Part 1.2), • SLO 1.4 define heritability and explain its significance in breeding decisions (Linked to Part 1.2), • SLO 1.5 describe the sources of genetic and phenotypic variation in livestock populations (Linked to Part 1.2),

AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS • SLO 1.6 explain how breeding objectives and economic traits are defined in livestock programmes (Linked to Part 1.3), • SLO 1.7 describe the breeding cycle and the role of selection within it (Linked to Part 1.3), • SLO 1.8 explain genetic gain and the factors that influence its rate (Linked to Part 1.3), • SLO 1.9 describe the breeding priorities for cattle, small ruminants, pigs, and poultry in Nigeria (Linked to Part 1.4), and • SLO 1.10 evaluate the contribution of animal breeding to food security and agricultural development in Nigeria (Linked to Part 1.1, Part 1.4). 1.1 Definition, Scope, and Importance of Animal Breeding 1.1.1 Definition and scope of animal breeding Animal breeding is the science and practice of changing the genetic composition of livestock populations through controlled mating, selection, and other reproductive interventions to improve economically important traits over successive generations. It is distinguished from animal husbandry in that it focuses specifically on the genetic component of animal performance rather than the environmental management of individual animals. The scope of animal breeding encompasses population genetics (the study of gene frequencies and how they change), quantitative genetics (the analysis of continuously varying traits such as milk yield and growth rate), and reproductive technology (methods such as AI and embryo transfer that multiply the use of superior genetics). Modern animal breeding also incorporates molecular genetics and genomics, which allow direct measurement of an animal's DNA to predict its genetic merit for production traits without waiting for offspring performance. This development has dramatically accelerated genetic improvement in dairy cattle, pigs, and poultry worldwide. In Nigeria, the application of these tools remains limited, but the foundational principles of selection, mating systems, and performance recording that underpin advanced breeding are directly applicable to smallholder and commercial livestock systems at any scale.

AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: The branch of breeding science that analyses continuously varying traits such as milk yield is called ______ genetics. 1.1.2 Historical development of animal breeding The history of animal breeding begins with the domestication of livestock approximately 10,000 years ago, when early farmers began selecting the most tractable, productive, and reproductively prolific animals for continued breeding. This empirical selection, based entirely on observable traits without any understanding of heredity, gradually shaped the domesticated breeds we recognise today. The work of Robert Bakewell in 18th-century England, who systematically improved Longhorn cattle and Leicester sheep through rigorous selection and inbreeding, is considered the first scientifically deliberate livestock improvement programme. Gregor Mendel's discovery of the laws of inheritance in 1866 laid the genetic foundation for modern breeding. The early 20th century saw the development of quantitative genetics by Ronald Fisher, Sewall Wright, and J.B.S. Haldane, who showed that the inheritance of continuously varying traits could be explained by many genes each with small effects. The introduction of artificial insemination (AI) in the mid-20th century allowed a single superior sire to produce hundreds of thousands of offspring, transforming dairy cattle improvement globally. The sequencing of livestock genomes in the early 21st century and the development of genomic selection have further revolutionised the speed and accuracy of genetic evaluation. Fill in the blank: The first scientifically deliberate livestock improvement programme was conducted by ______ Bakewell in 18th-century England.

AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: Key milestones in the history of animal breeding 1.1.3 Importance of animal breeding in livestock production Animal breeding contributes to livestock production by permanently and cumulatively improving the genetic potential of animals for economically important traits. Unlike management improvements, which must be paid for repeatedly each generation, genetic gains achieved through selection are retained and accumulate over time without additional cost. In the dairy industry, genetic improvement through AI programmes has been responsible for a doubling of milk yield per cow over the past 50 years in developed countries, reducing the cost of production per litre and improving farm profitability. In Nigeria, animal breeding is important for improving the productivity of indigenous livestock breeds that are well adapted to tropical conditions but produce at low levels. By selecting the best-performing animals within local breeds and, where appropriate, introducing exotic genetics through crossbreeding, producers can increase milk yields, growth rates, feed conversion

AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS efficiency, and reproductive performance. These improvements directly contribute to household food security, income generation, and the national agricultural development agenda. Fill in the blank: Unlike management improvements, genetic gains from selection are ______ and accumulate over time without additional cost. Pilot questions 1.1 1. Define animal breeding and distinguish it from animal husbandry. 2. Name the three main branches of science that constitute the scope of animal breeding. 3. Describe the contribution of Robert Bakewell to the development of animal breeding. 4. Explain how artificial insemination transformed genetic improvement in the 20th century. 5. State three ways in which animal breeding contributes to livestock production in Nigeria. 1.2 Key Concepts in Animal Breeding 1.2.1 Genotype, phenotype, and the environment The genotype of an animal is the complete set of genes it carries, inherited from its parents. The phenotype is the observable or measurable expression of those genes, such as body weight, milk yield, coat colour, or litter size. The relationship between genotype and phenotype is not one-to-one: the same genotype can produce different phenotypes depending on the environment in which the animal is raised. The basic model is: Phenotype = Genotype + Environment + Genotype x Environment interaction. This model reminds breeders that the performance they observe is a product of both genetic and non-genetic influences. The environment includes all non-genetic factors that influence performance: feeding level and diet quality, housing, climate, disease pressure, management, and the age and parity of the

AGE la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS animal. Because breeders aim to change only the genetic component of performance, they must correct for environmental effects when comparing animals for selection purposes. Failure to account for environmental differences leads to incorrect ranking of animals and poor selection decisions. This is

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