Animal breeding
Animal breeding improves livestock for more milk, meat, eggs and wool. Inbreeding mates related animals; outbreeding mates unrelated ones, as in crossbreeding.
Aims of animal breeding
- More milk, meat, eggs and wool.
- Resistance to diseases.
- Faster growth and earlier maturity.
- Better draught power, the strength to pull ploughs and carts.
Methods of animal breeding
| Method | What is done | Example or effect |
|---|---|---|
| Inbreeding | Closely related animals of the same breed are mated for several generations | Gives pure lines and exposes harmful genes so they can be removed. Too much causes inbreeding depression (lower fertility and yield). |
| Outcrossing | Unrelated animals of the same breed are mated (no common ancestor for 4 to 6 generations) | Overcomes inbreeding depression; helps animals with low milk yield or slow growth |
| Crossbreeding | Superior males of one breed are mated with superior females of another breed | Hisardale sheep, from Bikaneri ewes × Merino rams, developed in Punjab |
| Interspecific hybridisation | Animals of two related species are mated | Mule, from a male donkey and a female horse: strong and hardy, but sterile |
Breeds to know
| Animal | Breeds | Known for |
|---|---|---|
| Indian dairy cattle | Sahiwal, Red Sindhi, Gir | Good milk; resist heat and disease |
| Tamil Nadu cattle | Kangayam, Umblachery, Bargur, Pulikulam | Strong draught animals; Pulikulam bulls are known in jallikattu |
| Exotic dairy cattle (from other countries) | Jersey, Holstein-Friesian, Brown Swiss | Very high milk yield |
| Buffalo | Murrah | High milk with high fat |
| Poultry | Aseel (Indian), White Leghorn (exotic) | Aseel: hardy, good meat. White Leghorn: many eggs |
Inbreeding vs outbreeding
Hybrid vigour means the young are better than both parents in some traits, such as growth or milk yield.
Artificial insemination
In artificial insemination, semen is collected from a chosen superior bull and stored frozen. A trained vet places it into the reproductive tract of the female. One good bull can then father calves in many villages. It also avoids carrying the bull from place to place and lowers the spread of disease.
Many dairy farmers in Tamil Nadu keep crossbred cows (local cows crossed with Jersey or Holstein-Friesian) because they give more milk. Kangayam bulls, bred for ploughing, are part of our farm heritage.
2 marks: “What is inbreeding depression? How is it overcome?” A fall in fertility and productivity caused by continued close inbreeding. It is overcome by outcrossing with an unrelated animal of the same breed.
2 marks: “How was Hisardale sheep developed?” By crossbreeding Bikaneri ewes with Merino rams, in Punjab.
4 marks: “Explain the methods of animal breeding with examples.” Inbreeding (pure lines, inbreeding depression); outbreeding: outcrossing, crossbreeding (Hisardale sheep), interspecific hybridisation (mule); artificial insemination.
In = within the family. Out = outside it: outcross (same breed), crossbreed (two breeds), hybridise (two species).