Effects of marked chromosome sections on milk performance in cattle.

The investigations of paternal half sibs start with the assumption that the transfer of an allele from a father to an offspring also indicates the inheritance of a distinct section of two homologous chromosomes from the father concerned. With the help of 20 gene systems, the transfers of single chromosome sections were marked and tested with regard to influences on milk performance traits. 1,457 German Friesian cattle, registered as daughters of three sires, were used. Some of the chromosome sections showed significant effects on the traits considered. Since especially those chromosomes which bear genes for milk proteins were involved, it was assumed that groups of linked loci influence the genetic variance of milk production. Possibilities for applying the results to the practical breeding situation and their significance are discussed.