BREEDING VALUE ESTIMATION ON THE BASIS OF INBRED PROGENY - AN OVERVIEW

Inbreeding systematically redistributes the genotypes of a population and thus modifies both the additive genetic variability and the variance of dominance. Under the consequent exclusive presence of genetic variance, the covariance between parents and progeny increases by a factor of 1.5 after inbreeding. In view of this, it might be assumed that there are advantages in evaluating animals on the basis of their inbred progeny. The present paper comes to the conclusion that this assumption must be restricted to the special case in which non-additive genetic variance ( = variance of dominance) is absent. Since inbred progeny receive identical genes from both the father and the mother animal, the covariance between parents and inbred progeny will be influenced by corresponding nonadditive genetic effects in the presence of dominance. Therefore, in view of the regular depression of most useful traits through inbreeding, the systematic estimation of breeding value from inbred progeny does not seem to be possible with sufficient accuracy. The regular production of pure-bred progeny without inbreeding should still form the basis of reliable general breeding value estimation in stock breeding practice, especially in the case of sex-limited traits.