Mating of good quality animals to produce highly productive and suitable animals for enhancement of overall performance in the subsequent generations and to augment production and profitability is termed animal breeding.
There are two types of mating of animals for production of the progenies. These are
Natural propagation/mating : Mating of animals by natural means.
Artificial insemination (AI) : Mating is done through artificial means by collecting semen from male and the inseminating the females. This method help in use of outstanding males for mating of a large number of females thereby production of large number of highly productive and performing progenies.
System of breeding
Basically, there are two methods of breeding which are as follows:
Inbreeding : Breeding of the related animals as sire (male) and dam (female) are known as inbreeding.
Out breeding : Out breeding of unrelated animals as male and female is known as out breeding.
Inbreeding i.e. mating of related individuals often results in a change in the mean of a trait.
Performance of inbred animals lowers down the reproductive efficiency and may have several disorders. Hence, this method of breeding is not practiced for livestock improvement.
However, inbreeding is intentionally practiced to create genetic uniformity of laboratory stocks and to produce stocks for crossing (animal and plant breeding).
But inbreeding is unintentionally generated by keeping small populations for breeding and during selection.
There are again two types of inbreeding which are:
Close breeding : This is most intensive breeding where animals are very closely related and can be traced back to more than one common ancestor. Examples: Sire to daughter Son to dam Brother to sister.
Line breeding : Mating animals that are more distantly related which can be traced back to one common ancestor. Examples: Cousins Grandparents to grand offspring, Half-brother to half-sister. Line breeding increases genetic purity amongst the animals of progeny generations.
Out breeding system i.e. breeding of unrelated animals is generally of two types:
Crossbreeding: Crossbreeding is the mating of two animals of different breeds. Superior traits that results in the crossbred progeny from crossbreeding are called hybrid vigor or heterosis.
Grading up is the breeding of animals of two different breeds where the animals of an indigenous breed/genetic group is mated by an improved pure breed for several generations towards attaining the superior traits of the improved breed.
Grading up is continuous use of purebred sires of the same breed in a grade herd. By fifth generation, the graded animals may reach almost purebred levels.
By following out breeding system i.e., crossbreeding, selective breeding and grading up according to the need, results in improvement in production performance of the crossbred/graded along with improvement in growth rate, reproduction and production.
General Considerations Regarding Crossbreeding Systems
Good record keeping of the animals is required for selection good quality of male and females for breeding. Records on milk production and age at first calving are two important characters besides others.
Calving difficulties may increase when crossing large breed sires with small breed dams and hence selection of animals/breeds should be done carefully.
Fewer calving problems if large breed dams are used. However, large breed dams have higher maintenance costs.
Artificial insemination allows access to better bulls which may be practiced.
Selection of breeding animals
Selection of good quality improved animals for breeding is done by allowing some animals to have offspring while preventing the animals with inferior quality from reproducing.
The process allows producing genetically superior animals. Emphasis has to be given on several traits when selecting breeding stock.