Question

Which method is commonly used for improved cattle breeds and why?

Answer 1

CROSS BREEDING is the most common method used for this perpose..
and it is so..because 
the cross breed between two varities will lead to the introduction of new and improved variety..

Answer 2

Cattle husbandry is undertaken for two reasons-to improve milk production and labour-intensive farming. Dairy animals (females) are used to produce milk and draught animals (males) are engaged for labour-related work in agricultural fields such as carting, irrigation, tilling etc. Cross-breeding between two successful cattle breeds, i.e. a high milk producing females and a tough draught male with the best qualities of both parents can offer a fresh, improved variety.

For instance, the intersection of universal varieties, for example, Jersey Brown, Swiss (with long lactation periods) and Indian varieties, for example, Red Sindhi, Sahiwal (with magnificent sickness opposition power) creates another assortment with characteristics of the two varieties.