Animal Improvement – SS3 Agricultural Science Lesson Note (First Term)

Animal improvement is the breeding and development of only those animals with the greatest merit, such as good feed conversion, fast growth, disease resistance and large egg size.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define animal improvement.
2. State the objectives of animal improvement.
3. Highlight the processes of animal improvement.
4. Differentiate between the types of selection and the types of breeding.
5. Describe artificial insemination, with its advantages and disadvantages.

What are the objectives of animal improvement?

The objective of animal improvement is to produce animals that yield more, mature early and resist disease.

• High yield: animals that give more and better meat, milk or eggs.
• Feed conversion: animals that turn feed into body weight or products efficiently.
• Growth rate: animals that grow fast and reach maturity early.
• Adaptation: animals that cope with varied climatic conditions.
• Resistance: animals that withstand diseases and parasites.

What are the processes of animal improvement?

There are three processes of animal improvement: introduction, selection and breeding.

What is introduction?

Introduction is the bringing of high-quality livestock breeds into a farm or country from another farm or country.

• Quality of the breeds: they have high productive capacity and other desirable characteristics.
• Exotic breed: an imported breed that is not native to the country.
• Local breed: a breed that is native to the area.

How do local breeds differ from exotic breeds?

• Balance: exotic breeds are mated with local breeds to give cross-breeds.
• Result: the cross-breeds combine the good qualities of both parents.

What are the advantages of introduction?

• New breeds: it brings in breeds not originally present in the home country.
• Productivity: it gives greater productivity.
• Performance: breeds that adapt to the local environment may do better in quality and quantity.

What are the disadvantages of introduction?

• New diseases: it may bring new diseases to the area.
• New pests: it may bring new pests to the area.
• Adaptation: the animals may have problems adapting to the new area.
• Performance: the animals may not perform at their best.

What is selection?

Selection is the process of picking animals with breeding value from a mixed population to serve as parents.

• Purpose: to maximise genetic gain.
• Aim: to choose animals that pass their genetic attributes to their offspring.
• Examples of traits chosen: good meat production and good egg laying.

What are the types of selection?

There are two types of selection: natural selection and artificial selection.

• Natural selection: animals that withstand unfavourable environmental forces survive and reproduce, while the rest die off.
• Artificial selection: people choose and mate animals to improve the stock.

What are the types of artificial selection?

There are four types of artificial selection: mass, progeny, family and pedigree selection.

1. Mass selection: animals are kept or rejected on their own performance (merit), chosen from a large group.
2. Progeny selection: animals are chosen on the performance of their offspring. Parents of the best-performing offspring are kept.
3. Family selection: animals are kept or rejected on the performance of their relatives. It is usual when the family size is large.
4. Pedigree selection: animals are kept or rejected on the performance of their ancestors. It assumes that ancestors passed on their traits.

What are the advantages of selection?

• Best animals: only the best naturally available animals are chosen.
• Desirable traits: animals with good characteristics are selected.
• Distribution: animals from the best breeds are bred for distribution.
• Rejection: animals with undesirable characteristics are detected and removed.
• Disease control: it reduces the spread of diseases.
• Parasite control: it reduces the spread of parasites in breeding stock.

What are the disadvantages of selection?

• Slow: it is tedious and time-consuming.
• Costly: it takes much time and money.
• Expertise: it needs skills that may not be readily available.
• Loss of traits: some desirable traits of the parent stock may be excluded.
• No new traits: no new desirable characteristics are introduced.

What is breeding?

Breeding is the development of animals by passing inherited qualities from parents to offspring through mating.

What are the types of breeding?

There are four types of breeding: in-breeding, line-breeding, cross-breeding and out-breeding.

• In-breeding: mating of animals more closely related than the population average, such as father to daughter, son to mother or brother to sister.
• Line-breeding: mating of animals that are related but not too closely, such as cousins.
• Cross-breeding: mating of proven animals from different breeds, which may increase hybrid vigour.
• Out-breeding: mating of unrelated animals within the same breed.

• Line-breeding note: it has the same disadvantages as in-breeding, but the undesirable traits take longer to appear.
• Cross-breeding example: a trypanosomiasis-resistant breed such as N’Dama is crossed with White Fulani, which is susceptible. The hybrid combines the good qualities of both.
• Out-breeding note: it is the opposite of in-breeding and gives offspring with greater vigour and productivity.

What is the difference between in-breeding and out-breeding?

In-breeding is the mating of closely related animals. Out-breeding is the mating of unrelated animals of the same breed.

What are the advantages of breeding?

• Hybrid vigour (heterosis): mating superior animals from two breeds gives offspring better than the average of either parent (cross-breeding).
• Fast growth: offspring grow more rapidly and are more economical to rear (cross-breeding).
• Pure lines: it produces pure breeds (in-breeding).
• Preserving qualities: it concentrates and keeps specific qualities in an animal (in-breeding).
• Hardiness: offspring withstand changes in the environment (cross-breeding).

What are the disadvantages of breeding?

• In-breeding depression: a fall in vigour and performance (in-breeding).
• Lower output: milk, egg and meat production drop, growth slows and fertility is lost (in-breeding).
• Poor resistance: animals may resist diseases poorly (in-breeding).

What are the methods of animal improvement?

Artificial insemination is a method of animal improvement that uses stored semen in place of natural mating.

What is artificial insemination?

Artificial insemination is the introduction of semen into the female reproductive tract by a method other than natural mating.

• Storage: semen with spermatozoa is handled carefully, diluted and stored in liquid nitrogen at -196 °C.
• Timing: it is introduced during the heat period so that fertilisation occurs.
• Limit: it works only in animals whose heat period is easy to observe.
• Reason for timing: spermatozoa stay viable for only a few hours in the female tract.

What are the steps of artificial insemination?

1. Collect semen from a proven male.
2. Dilute the semen carefully.
3. Store it in liquid nitrogen at -196 °C until needed.
4. Watch the female and detect her heat period.
5. Introduce the semen into her reproductive tract at the right time.

What are the methods of collecting semen?

There are four methods of collecting semen from a proven male.

• Artificial vagina: the male mounts and ejaculates into a device that imitates the vagina.
• Massage method: the male is massaged to make him ejaculate.
• Electro-ejaculation: a mild electric current makes the male ejaculate.
• Recovery from the vagina: semen is taken from the female’s vagina after natural service.

What are the advantages of artificial insemination?

• Cost: it is easier and cheaper than natural mating, since the farmer need not keep a herd of males.
• Importation: it is easier and cheaper to import semen of exotic breeds than the animals.
• Best males: the best male can be used to a large extent.
• Many offspring: many females of different sizes can be served.
• Disease control: it reduces the spread of venereal and infectious diseases.
• Progeny testing: the offspring of one male can be tested in a short time.
• Long use: the semen of a good bull can be used long after the bull dies.

What are the disadvantages of artificial insemination?

• Expertise: it needs skills that may not be readily available.
• Heat detection: difficulty in detecting heat may limit success.
• In-breeding: its effects may show if only a few bulls are used in one area.
• Poor handling: wrong timing in the oestrus cycle can give a very low pregnancy rate.

Evaluation

1. Define animal improvement.
2. State the objectives of animal improvement.
3. Name the three processes of animal improvement.
4. List the four types of artificial selection.
5. State four methods of collecting semen for artificial insemination.

Assignment

Differentiate between in-breeding and out-breeding, giving one example of each.