Lesson Note
Subject: Agricultural Science
Topic: Animal Improvement
Lesson Objective: by the end of the lesson, the learners should be able to:
- Define animal improvement;
- State the aims of animal improvement;
- Describe processes of animal improvement;
- State the effects of each process in animal improvement;
- Explain the term ‘artificial insemination.
Lesson Summary/Discussion
DEFINITION OF ANIMAL IMPROVEMENT
The term Animal improvement can be defined as the ways of developing and breeding only those animals that show the greatest merit under consideration such as good feed conversion, growth rate, disease resistance and egg size. It also involves the upgrading of existing (local) breeds as a result of some desirable characteristics which they
possess.
AIMS OF ANIMAL IMPROVEMENT
1. To produce animals that can give high yield or products in form of meat, egg and milk.
2. To produce animals that can provide high quality of products such as low back-fat thickness, yolk size and shell hardness.
3. To produce animals with high feed
conversion efficiency.
4. To produce animals with high growth rate.
5. To produce animals with early maturity.
6. To produce animals which can adapt to climatic (environmental) conditions.
7. To produce animals that are resistant to parasites and diseases.
PROCESSES OF ANIMAL
IMPROVEMENT
There are three processes or methods of animal improvement. These are introduction, selection and breeding.
A. Introduction: Introduction is the process of bringing in high quality breeds of livestock with a high productive capacity and other good desirable characteristics from another farm or country. Before the introduction of such animal from another country (exotic breeds), one must be sure that such breeds possess higher quality characterisitics than the local breeds. Different breeds of farm animals exist and these inchude the local breeds, imported breeds and the cross breed.
The local breeds are usually smal
animals, slow-maturing, poor producers, but adapted to local environment and resistant to
many diseases. The exotic (imported) breeds are big animals, early-maturing, good producers
but may not adapt to local environment and not be resistant to many diseases. To obtain a balance, the exotic breeds are used to mate the local breeds to obtain cross breeds which will now combine all the good qualities of exotic and local breeds.
Advantages of Introduction
1.Breeds which are not originally present in the home country are introduced.
2. It enhances greater productivity.
3.It leads to the absence of pests and
diseases.
4. Breeds may perform better in terms of quality and quantity, if they are able to adapt to local environment.
Disadvantages of Introduction
It may introduce new diseases to the
area.
2. It may introduce new pests to the area.
3. It may have the problem of adaptation to the new area.
4. It may not perform maximally.
B. Selection: Selection is the process of picking or selecting from a mixed population those animals with breeding value as parents.
Selection is undertaken to maximise genetic gain.
It helps to select animals that are capable of transmitting their genetic attributes to their offspring. Animals with desirable characteristics like good meat production, egg laying, etc are selected. Selection is grouped into two main classes.
i. . Natural selection: This is the ability of individual animal to weather through unfavourable environ-mental forces to survive and reproduce. Those that are unable to survive die off.
ii. Artificial selection: This selection is done by man using his intelligence and influence to select and mate animals in order to increase the number of animals.
There are four types of artificial selection.
a. Mass selection: Animals are selected or rejected on the basis of their own
performance (merit). Animals with the desired characteristics are chosen in preference to those not possessing them from a large group of animals.
b. Progeny selection: Animals are selected on the performance of their
progeny or offspring. Mothers of the
best performed offspring are retained
while the mothers of offspring that do
not perform well are discarded.
Family selection: Animals are selected
or rejected on the basis of the
performance of the relatives or family
It is useful when family size is large.
Pedigree selection: Animals are
selected or rejected on the basis of the performance of their ancestors. This selection is based on the belief that ancestors have passed on their traits to the animals being considered and so the animals are likely to perform equally or even better than the ancestors.
Advantages of Selection
- It ensures that only the best naturally available animal is selected.
- Animals with desirable characteristics are selected.
- Animals from best breeds are bred for distribution.
- Animals with undesirable characteristics are detected and rejected.
- Selection reduces the spread of diseases.
- It also reduces the spread of parasites associated with breeding stocks.
Disadvantages of Selection
- Selection is tedious and time-consuming.
- It is very costly in terms of time and money.
- It requires expertise which may not be readily available.
- It brings about elimination or exclusion of some desirable traits of some parent stock.
- No new desirable characteristics are introduced.
C. Breeding: Breeding involves the development of animals by transfering inherited qualities from parents to offspring. This is achieved through
mating.
Types of Breeding
a. In-breeding: This involves the mating of more closely related animals than the average of the population from which they come, eg the mating of father to daughter, son to mother or brother to Sister.
Importance of In-breeding
- It produces offspring with undesirable characteristics because of recessive genes showing up.
- It also enables the farmer to get desired character or quality well developed in an animal.
- In-breeding helps to produce inbred lines that can be used for cross breeding to produce hybrid vigour.
- It also leads to in-breeding depression.
b. Line-breeding: This is closely related or similar to in-breeding.
It involves the mating of not too closely related animals, e.g., mating between cousins.
Importance of Line-breeding
It has the same disadvantages as in-
breeding, but it takes a longer period for undesirable traits of the parents to appear (i.e in-breeding depression).
It is used to consolidate traits for a sire or dam. Most of the high quality
commercial characters developed recently have been as a result of line-breeding.
c. Cross Breeding: This is the mating of proven quality animals from different breeds.
Importance
- It may lead to an increase in hybrid vigour, e.g., the cross between muturu breed of cattle which is resistant to trypanosomiasis and White Fulani which is susceptible to the disease to produce a hybrid which combines the good qualities of the two breeds.
- It results in breeds of animals with higher production capacity than any of the parents.
- It brings about greater rate of growth in an ofispring.
- It produces individuals offspring that canwithstand climatic variations in the environment.
- It also promotes higher yield of eggs.
- It increases disease resistance in meat and milk in offspring.
d. Out-Breeding: This is the mating of unrelated individual animals within the same breed. Out-breeding is the opposite of in-breeding. It produces offspring with greater vigour and productivity.
Advantages of Breeding
1.The crossing or mating of superior
animals from two different breeds produces an offspring that is superior to the average of either parent. This is called hybrid vigour or heterosis (cross breeding).
2. Offspring grows more rapidly and is more economical to rear (cross breeding)
3. It results in the production of pure breeds or pure lines (in-breeding).
4. It helps to concentrate and preserve specific qualities in an animal (in
breeding).
5. Offsprings produced can withstand
variations within the environment (crossbreeding).
Disadvantages of Breeding
1. It may result in in-breeding depression, i.e., a reduction in vigour and performance (in-breeding).
2. It can also result in drop in production such as milk, egg, meat, slow growth rate, loss of fertility (in-breeding).
3. It may also result in poor resistance to diseases (in-breeding).
D. ARTIFICIAL INSEMINATION
This is the introduction of semen into the reproductive tract of the female by a method other than natural mating. The semen containing spermatozoa are carefully handled, diluted and stored in freezer at a temperature of 196°C in liquid nitrogen until it is required for use.
For artificial insemination to succeed, the semen which has been stored is introduced into the female reproductive tract during breeding
cycle (the heat period) so that fertiliization will occur. Artificial insemination is only possible in
animals whose heat period is easily observable because spermatozoa are only viable for few hours after introduction into the female reproductive tract.
Methods of collecting semen from a proven male for use in artificial insemination are:
- Artificial vagina
- Massage method
- Electro-ejaculation
- Recovery of semen from the vagina after service.
Advantages of Artificial Insemination
- It is easier and less expensive than natural mating since the farmer is saved the expense of maintaning a herd of male animals.
- It is easier and cheaper to import the semen ofexotic breeds rather than the male animals themselves.
- It makes it possible to use the best male animal to a large extent.
- It is possible to service many females of different sizes leading to the production of many ofisprings.
- It brings about reduction in the transmission of venereal and infectious diseases.
- It allows for the testing of offspring of a particular individual within a relatively short period of time.
- The semen of a good bull can still be used long after the death of the bull.
Disadvantages of Artificial Insemination
- It requires expertise which may not be readily available.
- Difficulties in detecting heat in female animals may limit the success of artificial insemination.
- In-breeding effects may show up if only a few bulls are used in a particular environnment.
- The handling procedure is inadequate (i.e, improper timing of breeding in the oestrus cycle), the pregnancy rate may be very low.
Lesson Evaluation/Test
1.What is animal improvement?
2. State six aims of animal improvement.
3. Briefly discuss the processes of animal improvement and state two advantages and two disadvantages of each process.
Briefly explain the following:
- mass selection
- pedigree selection
- in-breeding
- cross-breeding
Questions answered correctly? Kudos👍
Do stay connected for more lesson contents.