1. Selection for desirable qualities — Selection is the most widely practiced method of maintaining and improving domestic animals. But wise application of this type of selection is not as easy as it may seem to be. Selection on the basis of one factor alone is often found to lead to nothing. For example, if one selects and breeds hens on the basis of the size of eggs laid down and after several generations a flock of hen is developed which laid eggs distinctly larger than the average. But the hens of this flock were found to be susceptible to some disease. Therefore, during artificial selection all the desirable qualities should be taken into account.
2. Progeny test — in many domestic animals only one sex is commercially valuable. As for example, females are directly concerned with egg yield and egg-size, but the rooster has just as much to do with the yield and size of the eggs as the hen. If male parent is ignored, half of the effectiveness of the selection is gone. Yet, how can we determine a rooster’s genes for egg production? This can be determined by progeny test, i.e. by breeding and studying the offspring’s. The principle of progeny test is well illustrated by specific example in the breeding of dairy cattle. A large dairy purchased a young bull which had taken many prizes in the show and which had a fine pedigree. But the female calves obtained from such crosses for which this bull was used as sire, produced milk below that of their mothers. Contrary to this, another bull that was not so impressive from its look produced daughters with a high yield of milk. This indicates that the prized bull did not have genes required for the purpose.
3. Inbreeding— for most prized, pedigreed animals, the ancestry record frequently shows that individual animals appear more than once in a given line of ancestry. Therefore, practice of inbreeding is essential for uniformity in the race by establishing homozygosis. Since there is a decrease in size, vigour and fertility among the descendants of inbred stock, this can be counterbalanced to some extent by combining inbreeding with selection so as to eliminate the deleterious effects of homozygous harmful recessive genes. Ptolemies of Egypt, in order to perpetuate the fine qualities of their line, practiced brother-sister marriages for many generations, ending with the famous sires of the Nile, Cleopatra.
4. Outbreeding— the commercial benefits which may be gained by selection and inbreeding within any particular strain of a population are necessarily limited to those genes which are already present in the strain. These methods can simply sort out the various hereditary potentialities in the germplasm, but it could not yield new combinations. New genes can be introduced by cross breeding or outbreeding. In this manner it is possible to pick up new gene combinations which may be of great value to man.
Methods of Animal Breeding
What are Positive Eugenics?
1. Selective Mating — the family histories should be checked thoroughly before settling the marriage and persons with defective pedigrees should be avoided. On the other hand persons with normal or talented family histories should be preferred for marriage. It is a fact that children from healthy parents are always healthy and intelligent.
2. Removal of Social Hindrances — Social rules and regulations put hindrances in the way of marriages. Religion, castes, racialism and dowry are major hindrances, as a result of which good germplasm from different sources fails to come together. These social hindrances should be removed and inter-caste, inter-racial and inter-religion marriages should be encouraged. These marriages bring together two different lineages and provide an opportunity for mixing of two gene pools. The combinations may prove useful.
3. Early Marriage and Prevention of Loss or Wastage of Good Germplasm — Often marriages are made late in life time. It is especially true, of highly placed persons having great ambition for their career. In achieving their ambition they sacrifice best part of their youth remaining unmarried. Majority of scientists, politicians, poets and writers, etc. prefer to remain unmarried. The biological and psychological investigations have revealed that emotional warmth and sexual activities decrease with age and moreover, the germplasm also loses its vigour. Therefore, good germplasm goes waste. Early marriages of superiors should be encouraged to produce more offspring’s. The intellectuals, philosophers, scientists, braves, politicians should be subsidized to produce their kind. During war braves and intellectuals are killed and mutilated. This also leads to wastage of good germplasm. Therefore, war should be avoided as a eugenic measure.
4. Preservation of Good Germplasm — H.S. MULLER has suggested that the germplasm (semen and ova) of outstanding persons may be preserved and may be used for artificial insemination. Thus these persons could serve to be the father of many more children than would be otherwise. Very recently scientists felt the urgent need of establishing sperm and egg banks to protect the precious germ cells from radiation and age effect. The germ cells could be collected in adulthood and stored in lead-lined containers in deep freeze.
5. Eugenic Consultation or Genetic Counseling— Eugenics may be applied most efficiently in the form of consultation before marriage. Doctors with good knowledge of genetics could be made available at definite centers, which could provide the proper guidance.
