Is artificial selection in Italian Holstein Friesian cattle favouring heterozygotes?

Abstract

In recent years, the genetic analysis of cattle breeds has shown that most of the genetic variability is located within breeds instead that between breeds (Mac Hugh et al., 1998). Moreover, the amount of genetic diversity assessed within breeds is quite high (Edwards et al., 2000). A selection pressure in favour of the heterozygotes can be a possible explanation for this. In this case the management of cattle breeds would represent a tool to preserve genetic variability, instead of the cause of its decline. The Italian Friesian is the main Italian dairy cattle breed. The herd book has been created in 1959 and is managed by the ANAFI (National Association of Italian Friesian Breeders). Each year ANAFI updates the herd book and uses productive data for computing genetic evaluations by an animal model analysis. These genetic evaluations are available to the farmers who use them to choose semen for artificial insemination.........