Breeding is defined as the crossing of the male and the female parents to get the off spring for the characters desired. The main breeding methods are:
1) In Breeding
2) Out Breeding
They are further classified as given in the chart below:
Inbreeding is the mating of closely related individuals, whose relationship is more than the average relationship of the population. The example is the individual having one or more common ancestors or relatives. The measures of inbreeding is the coefficient of inbreeding. Inbreeding may be close inbreeding or line breeding.
(a) Close inbreeding:
In this type of inbreeding, mating is made between very closely related individuals, such as full brothers are crossed with full sisters, or off springs are crossed with parents.
(b) Line breeding
It is repeated back crossing to one outstanding ancestor, so that its contribution to the progeny is more. In this type of breeding, matings are made to concentrate the inheritance of desired characters of some favoured individuals.
a) It brings about the uniformity of the required type.
b) The dangers involves in case in breeding can be reduced.
Advantages of Inbreeding:
- Undesirable recessive genes may be discovered and eliminated by further testing in this line.
- It increases homozygosity and decreases genetic variance.
- Breaking down of population into different inbreed lines.
Disadvantages of Inbreeding:
- The progeny becomes more susceptible to diseases.
- Breeding problems and reproductive failure usually increases.
- It is difficult to find out the stage of breeding at which it should be discontinued, in order to avoid the bad effects of the system.
- It depresses’ vitality in early life than in later life.
- A small breeder stands a good chance of gain by doing too much in breeding.
- Inbreeding appears to have little value in dairy cattle breeding programmes, because of its numerous detrimental effects.
It is the opposite of inbreeding. Mating unrelated animals is known as out breeding. It is divided into six classes as detailed below:
a) Pure breeding
b) Line Crossing (Crossing of inbreed lines)
c) Out Crossing
d) Cross Breeding
e) Grading up
f) Species Hybridisation
(a) Pure breeding:
It is mating of male and female belonging to the same breed. Pure breeding is a sort of out breeding. The examples of pure breeding are:
- Ongole Cow x Ongole bull
- Jersey Cow x Jersey Bull
- Murrah she buffalo x Murrah bull
The outstanding advantage of pure breeding is for production of bulls for breeding purpose only pure breeding is to be followed in almost all the breeds except in case of inter-se-mating. It avoids mating of closely related individuals.
(b) Line crossing:
In this method of breeding closely inbred lines by intensive in breeding of more than 5 generations is done to develop in bred lines, from unrelated line for the male and for the female. The unrelated inbreed line male is matted to the inbred lines of female and the offspring born out of such mating becomes a hybrid which exhibits heterosis or hybrid vigour. Heterosisis the phenomenon where in the crosses between inbreed lines or parned populations are exceed., Even the better of the two parental populations, it is caused by the non-additive genetic effects. At luminance and epistasis, which arise from increased hetrozygosity.
( c) Out crossing:
It is mating of unrelated pure bred animals in the same breed. The animals do not have common ancestors on either side of their pedigree upto 4 to 6generations and the offsprings of such a mating is known as the Out cross.
Advantage: It is an effective system for genetic improvement if carefully combined with selection. It is also pure breeding.
(d) Cross breeding:
It is mating of animals of different breeds. Cross breeding is followed for breeding animals for milk production and meat production. In India zebu breeds of cows and nondescript cows are crossed with exotic breeds like Holstein Fresian, Brown Swiss and Jersey bulls or their semen, to enhance the milk production potential of the progeny.
Advantages of cross breeding:
- The desirable characters of the exotic parent are transmitted to the progeny which the indigenous parent does not have.
- In India Cross-breeding and cows is done by using the exotic bulls and the progency inherit the desirable characters of the parent like high milk yield early maturity, higher birth weigh of calves, better growth rates, better reproductive efficiency and indigenous parents characters like, heat tolerance, disease resistance ability to thrive on scanty feeding and coarse fodder etc.
- In pairs the way to evolve new breeds with desirable characters.
- Hybrid vigour is made use of in the progency
- Results are seen more quickly in characters like milk yield in the cross bred progeny.
Disadvantages of cross breeding:
- The breeding merit of cross breed animals may be slightly reduced.
- Cross breeding requires maintenance of two or more pure breeds in order to product the cross breeds.
(f) Grading up:
Grading up is the practice of breeding in which the sires of the exotic breed are mated with the non-descript females and their off-spring from generation to generation. After five or six generations of grading up -a population resembling the exotic breed results. This is the breeding policy that is pursued in India.Females of less developed breeds or nondescript buffaloes are continuously bred by Murrah bulls. After 5 to 6 generations the grades carry 96.9 % to 98.4 % of exotic inheritance respectively:
Advantages of grading up:
- After 5 to 6 generations grades resembling pure bred animals in matter of physical appearance and production can be obtained.
- Grading up avoids callosal expenditure of purchasing the exotic females herd of animals as grading up is carried on with a few exotic bulls and the indigenous female animals.
- It proves the breeding merit of the exotic bulls used.
- The value of the graded animals is much enhanced.
Disadvantages of grading up:
- The graded males are useless for breeding purpose
- The climate and the environment that is suitable for the exotic breed only is suitable for grading also. If the place is not suitable for the exotic breed it is not suitable for grading with that breed.,