Biology ANIMAL BREEDING

KEY TOPICS

`star` Animal Breeding
`star` Inbreeding
`star` Outbreeding
`star` Outcrossing
`star` Crossbreeding
`star` Interspecific Hybrisation

ANIMAL BREEDING


● `color{Brown}"Breeding"` of animals is an important aspect of `color{Violet}"animal husbandry"`.

● Animal breeding aims at `color{Violet}"increasing the yield"` of animals and improving the `color{Violet}"desirable qualities"` of the produce.

● A group of animals `color{Violet}"related by descent"` and `color{Violet}"similar in"` `color{Violet}"most characters"` like general appearance, features, size, configuration, etc., are said to belong to a `color{Brown}"breed"`.

● When breeding is between `color{Violet}"animals"` of the `color{Violet}"same breed"` it is called `color{Brown}"inbreeding"` while crosses between `color{Violet}"different breeds"` are called `color{Brown}"outbreeding"`.




INBREEDING

● `color{Brown}"Inbreeding"` refers to the mating of more `color{Violet}"closely related individuals"` within the same breed for `color{Violet}"4- 6 generations"`.

● The breeding strategy is as follows – `color{Violet}"superior males"` and `color{Violet}"superior females"` of the same breed are identified and `color{Violet}"mated in pairs"`.

● The `color{Violet}"progeny"` obtained from such matings are `color{Violet}"evaluated"` and superior males and females among them are `color{Violet}"identified for"` `color{Violet}"further mating"`.

● A `color{Brown}"superior female"`, in the case of cattle, is the cow or buffalo that produces `color{Violet}"more milk per lactation"`.

● On the other hand, a `color{Brown}"superior male"` is the bull, which gives rise to `color{Violet}"superior progeny"` as compared to those of other males.

● A similar strategy as used by `color{Violet}"Mendel"` in developing `color{Violet}"homozygous purelines"` is used for developing purelines in cattle as was used in case of peas.

● Inbreeding increases `color{Violet}"homozygosity"`.

● Thus inbreeding is necessary if we want to `color{Violet}"evolve a pureline"` in any animal.

● Inbreeding exposes `color{Violet}"harmful recessive gene"`s that are `color{Violet}"eliminated by selection"`.

● It also helps in accumulation of `color{Violet}"superior genes"` and elimination of `color{Violet}"less desirable genes"`.

● Therefore, this approach, where there is `color{Violet}"selection at each step"`, increases the productivity of `color{Violet}"inbred population"`.

● However, `color{Violet}"continued inbreeding"`, especially close inbreeding, usually `color{Violet}"reduces fertility"` and even `color{Violet}"productivity"`.

● This is called `color{Brown}"inbreeding depression"`.



● Whenever this becomes a problem, `color{Violet}"selected animals"` of the breeding population should be mated with `color{Violet}"unrelated superior animals"` of the same breed.

● This usually helps `color{Violet}"restore fertility"` and `color{Violet}"yield"`.

OUT BREEDING

● `color{Brown}"Out-breeding"` is the breeding of the `color{Violet}"unrelated animals"`, which may be

● `star` between individuals of the `color{Violet}"same breed"` (but having `color{Violet}"no common ancestors"`),

● `star` or between `color{Violet}"different breeds"` (`color{Brown}"cross-breeding"`)

● `star` or `color{Violet}"different specie"`s (`color{brown}"inter-specific hybridisation"`).


OUT-CROSSING

● This is the practice of mating of animals within the `color{Violet}"same breed"`, but having `color{Violet}"no common ancestors"` on either side of their pedigree up to `color{Violet}"4-6 generations"`.

● The offspring of such a mating is known as an `color{Brown}"out-cross"`.

● It is the `color{Violet}"best breeding method"` for animals that are `color{Violet}"below average"` in productivity in milk production, growth rate in beef cattle, etc.

● A single outcross often helps to `color{Violet}"overcome inbreeding depression"`.

CROSS BREEDING

● In this method, `color{Violet}"superior males"` of one breed are mated with `color{Violet}"superior females"` of `color{Violet}"another breed"`.

● Cross-breeding allows the `color{Violet}"desirable qualities"` of two `color{Violet}"different breeds"` to be combined.

● The progeny hybrid animals may themselves be used for `color{Violet}"commercial production"`.

● Alternatively, they may be subjected to some form of `color{Violet}"inbreeding and selection"` to develop new `color{Violet}"stable breeds"` that may be superior to the existing breeds.

● Many `color{Violet}"new animal breeds"` have been developed by this approach.

● `color{Brown}"Hisardale"` is a new breed of sheep developed in `color{Violet}"Punjab"` by crossing `color{Violet}"Bikaneri ewes"` and `color{Violet}"Marino rams"`.

INTERSPECIFIC HYBRIDISATION

● `color{Brown}"Interspecific hybridisation"`: In this method, `color{Violet}"male and female"` animals of two `color{Violet}"different species"` are mated.

● In some cases, the progeny may combine `color{Violet}"desirable features"` of both the parents, and may be of considerable
`color{Violet}"economic value"`, e.g., the `color{Brown}"mule"`.

 
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