Effect of Holstein crossbreeding on dairy traits in the French Black and White cattle population

Abstract

The French Black and White dairy cattle population has been crossbred with the Holstein strain. The percentage of Holstein genes reached almost 100% as early as 1980 for artificial insemination bulls and increased from 5 % in 1970 to 83 % in 1990 for females. Heterosis and recombination losses in Holstein x European Black and White cattle were estimated for milk, fat, and protein yields, and for fat and protein contents, from about 12.4 million records collected on about 5.6 million cows from 1975 to 1992. For yield traits, heterosis reached 2-2.5% of the mean, while recombination losses estimates were negative and reached 40 to 86% of heterosis. For contents, heterosis and recombination losses were very low. For yield traits, omitting these crossbreeding parameters in genetic evaluation led to a 10 to 20 % underestimation of the whithin strain genetic trend, and to a 10 % overestimation of the genetic differences between strains, which reached 1.5 genetic standard deviation, i.e. 20 kg protein.