Selective breeding is a modern agricultural technique used to genetically promote favorable characteristics in plants and animals. This is usually achieved through controlled breeding of high-yield plants and animals. The advantages of selective breeding include increased profitability and the ability to rid future offspring of disease and disability. The disadvantages include a loss of genetic variety and possible difficulties and discomfort in the animals' lives.
Selective breeding allows the promotion of characteristics more economically favorable to the farmer. For example, certain cows produce more milk on average than other cows; by breeding these cows with each other, the high milk yield gene will be passed on to the offspring. If implemented with plants, horticulturists growing roses can breed plants that produce a relatively high number of roses. The promotion of these favorable characteristics will increase the economic value of the organism.
Advances in genetic study now allow pre-screening and identification of certain genetic diseases. Controlled breeding of animals with no genetic diseases will eventually eradicate genetic diseases from future offspring.
Selective breeding often requires inbreeding of animals and plants. This decreases genetic variety in the gene pool. As genetic variety is lost, the organisms express similar susceptibility to specific pathogens. If a group of genetically similar animals or plants is attacked by a certain pathogen, genetic similarity increases the likelihood that the whole population will be vulnerable to the disease. Therefore, unless carefully monitored, selectively bred populations are constantly in danger of being wiped out by disease.
Breeders who seek to encourage certain desirable traits, may unintentionally reproduce traits detrimental to the animal's health. For example, for economic benefit, farmers may breed cows with large udders to increase their offspring's milk yield. These large udders may be too heavy for the cow to bear and cause great discomfort.
