INBREEDING

Wairarapa Times-Age, 20 December 1939, Page 3

INBREEDING

POINTS FOR AND AGAINST. * The farmer is often faced with the question as to whether he should dispose of a bull that he has been using for several years, or whether he should continue to use it —i.e., with its own offspring, according to a recent statement by Mr J. G. Nortje, a South African animal husbandry specialist. Mating a bull with its own heifer calves is known as inbreeding. There are other ways of inbreeding—e.g., son to mother or brother to sister. These are all cases of very close inbreeding. Says Mr’ Nortje: “On going into the history of our farm animals, we find that in building up the breed use was made of inbreeding at some stage or other in practically all cases. In spite of this, however, we find that breeders still hold different opinions as to how long or how closely inbreeding should be practised. Some of our most famous breeds owe their excellence to continuous and close inbreeding, which will be regarded with suspicion by most breeders. In this connection we find examples such as the Angora goat. “Experience and research work have, however, revealed certain facts that may serve as a guide in the breeding and improvement of our farm animals. The most important fact that should not be lost sight of is that inbreeding results in a concentration or intensification of practically all the characteristics of the parents in their offspring —i.e., of good as well as undesirable characteristics. As a rule, the results of inbreeding, therefore, depend upon the characteristics of the animals that are mated—i.e., the degree of success or failure depends upon the quality at the breeder’s disposal. ‘‘The important question we have to answer is: What is the genetic constitution of our animals? They may apparently possess, in a large degree, those desirable characteristics we are looking for, but the danger exists that they may also possess a hereditary tendency for a great number of undesirable characteristics which remain dormant, because the desirable characteristics are dominant. When such animals are subjected to inbreeding, a concentration of characteristics takes place that may result in a large percentage of the offspring being of inferior quality. For this reason it is extremely dangerous to allow inbreeding in the case of grade cattle. “By grade cattle we here mean animals that have not yet been bred purely for the salient characteristics of a particular breed. If a bull is taken from such a herd and mated with its sisters and mother, we may expect a large number of the progeny to be of inferior type on account of the fact that a concentration of characteristics, which we wish to eliminate, has taken place. In this case, therefore, inbreeding leads us further away from instead of closer to the ideal we are aiming at.