Breeding Systems

Animal breeding is an essential aspect of animal husbandry. It refers to controlled mating of animals followed by selection to obtain a superior genotype of animals. It helps increase the yield of animals, improves their reproductive rate, and develops resistance to various diseases in animals. 

The term ‘breed’ refers to a specific group of animals from the same or related lineage, having mostly similar characteristics like homogenous behaviour, appearance, features, and size. For breeding purposes, the mating of animals can be done in two ways: natural propagation/mating or artificial insemination. 

Breeding systems overview

There are two different breeding systems in India- inbreeding and outbreeding. Mating between closely related animals or genetically similar animals is known as inbreeding. When the breeding is done between non-related species, it is called outbreeding. 

Inbreeding 

Inbreeding involves the mating of closely related animals of the same species, that belong to the same breed, for successive generations. This system involves identifying and selecting superior males and females of the same breed, preferably from different populations and then mating them in pairs. 

The superior males and females obtained from such mating are then assessed for desirable traits and the best ones selected again for mating. For example, among cattle, a superior cow or a buffalo is recognized by its milk-producing capacity. A superior bull produces higher progeny in comparison to other males. This process of selection and mating is repeated for 4-6 generations. Bulls found unsuitable for breeding are castrated when they are young.

Types of inbreeding

Inbreeding can be further categorized into: 

1. Close inbreeding: This involves mating very close relatives such as parents and offspring (first-degree relatives) or full brothers and sisters with each other, or mating between second-degree relatives such as grandparents and grand-offspring, half brothers and sisters, uncles/aunts and nephews/nieces, and double-first cousins. 
2. Line inbreeding: It involves mating animals that are more distantly related, but have at least one common ancestor. For example, cousin grandparents to grand-offspring. 

Advantages of inbreeding

• Inbreeding leads to increased homozygosity, which is necessary to evolve a pure line in an animal breed.

• Inbreeding also leads to exposure and elimination of recessive genes that can be harmful.
• Inbreeding helps in accumulating the superior gene. Through selection, we can eliminate the less desirable genes, increasing the productivity of the inbred population. 

Disadvantages of inbreeding

• Inbreeding decreases life span, resistance, and milk production in dairy cows.
• Continued inbreeding, especially in closely related individuals, usually results in reduced fertility and productivity of the offspring. This phenomenon is called inbreeding depression. To overcome this problem and help restore fertility and yield, the superior animals of one population are often mated with some animals of another population, but of the same breed.

Outbreeding

Outbreeding refers to the mating between animals that share no common ancestry but are of the same breed, between animals of different breeds within the same species, or between animals of different species. Normally, those breeds are chosen that have complementary traits and will enhance the offspring’s economic value.

Types of outbreeding

1. Out-crossing: Mating of animals that do not share common ancestry for 4-6 generations but are of the same breed is termed out-crossing. 

• The offspring obtained from out-crossing is termed as an out-cross. 
• An out-cross helps in overcoming the problem of inbreeding depression.

2. Cross-breeding: The mating of superior males with superior females of non-related breeds is termed cross-breeding. 

• With this strategy, the desirable features of the two different breeds are combined, leading to the development of new superior breeds and improvement of the quality of local breeds. 
• A cross-breeding between White Shorthorn and the Black Angus cattle produces a Blue Room Hybrid that has the vigour, rapid growth, economic utilization of food, and high quality of beef. 
• Cows of inferior local breeds are often mated with bulls of superior exotic breeds. 

3. Inter-specific hybridization: When two animals of non-related species but the same genus are mated, it is known as interspecific hybridization. 

• This technique helps in improving genetic diversity within species. The progeny displays desirable traits and characteristics of both parents but is often sterile. 
• The sterile hybrid is far superior to either of the parents. For example, a mule is the offspring of a male donkey and a female horse. Mule is both sturdier and hardier than either of his parents and facilitates the transport of heavy articles in mountainous terrains.

Conclusion

Animal breeding is a vital aspect of animal husbandry. The main objective is to produce highly productive, disease-resistant, and superior breeds of animals. Such animals often have enhanced overall performance in the subsequent generations and increased production and profitability.