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Animal Breeding

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notes

Animal Breeding:

  • It is a process to produce improving breeds of domesticated animals by improving their genotypes through selective mating.
  • Animal breeding important part of animal husbandry to increase the yield of animals and improve desirable qualities in products.
  • A group of animals related by descent and similar in most characters like general appearance, features, size, configuration, etc., are said to belong to a breed.
  • The chief objectives of animal breeding may be summarised as follows:         
  1. Improved growth rate.  
  2. Increased production of milk, meat, egg, wool, etc. 
  3. Superior quality of resistance to various diseases. 
  4. Increased productive life.
  5. Increased or at least, acceptable reproduction rate, etc. 

A variety of strategies have been used for the breeding of animals. The main approaches for animal breeding, viz., inbreeding, out-breeding, out-crossing, cross-breeding, and interspecific hybridization are briefly described below which are based mainly on the breeding work with cattle. 

1) Inbreeding: 

  • When breeding is between animals of the same breed it is called inbreeding.
  • It is the mating of more closely related individuals within the same breed for 4-6 generations.  
  • The breeding strategy: Superior males and superior females of the same breed are identified and mated in pairs.  
  • The progeny obtained are evaluated and superior males and females are identified for further mating. 
  • In cattle, a superior female (cow or buffalo) produces more milk per lactation.
  • A superior male (bull) gives rise to superior progeny. 
  • Advantages of Inbreeding: 

  • Inbreeding increases homozygosity, i.e., it helps to evolve pure line breeds in any animal.
  • It exposes harmful recessive genes that are eliminated by selection. 
  • Accumulation of superior genes and elimination of less desirable genes. 
  • Therefore, this approach, where there is selection at each step, increases the productivity of the inbred population.
  • Disadvantages of Inbreeding: 

  • It can cause inbreeding depression which is the depression/reduction the fertility and productivity due to continued inbreeding, especially close inbreeding. 
  • To solve this problem, selected animals of the breeding population should be mated with unrelated superior animals of the same breed. This usually helps restore fertility and yield.

2) Out-Breeding: 

Outbreeding is the mating of unrelated animals, which can be between members of the same breed (but without shared ancestors), or between breeds (cross-breeding) or species (interspecific hybridization). 

3) Out-Crossing:

  • It is the mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4-6 generations. The offspring of such a mating is known as an out-cross.  
  • Best breeding method for animals that are below average in milk productivity, the growth rate in beef cattle, etc.  
  • A single outcross often helps to overcome inbreeding depression.

4) Cross-breeding: 

  • In this method, superior males of one breed are mated with superior females of another breed.
  • The desirable qualities of two different breeds are combined.
  • The progeny hybrid animals may be used for commercial production. 
  • Progeny hybrid may be subjected to some form of inbreeding to develop new stable breeds i.e., superior to existing breeds. E.g. Hisardale is a new breed of sheep developed in Punjab by crossing Bikaneri ewes and Marino rams.   

5) Inter-specific hybridization:

  • In this method, male and female animals of two different related species are mated. It may not be cent percent successful process. 
  • In some cases, progeny may combine desirable features of both the parents and shows economic value e.g., Mule.
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