[Fertility in relation to production in dairy cattle]

A review of the relationship between fertility of production in dairy cattle is presented. At farm level almost no relationship was found, except that farms in the lowest production class had lower fertility rates. Within farms there was a weak antagonistic relationship. Better dairy cows were first presented slightly later and needed more inseminations to achieve pregnancy. The genetic capacities for production and fertility appear, especially in the first lactation, to be negatively related. In older animals, the relationship was absent or even slightly positive. Animals with a lower productive capacity are generally culled earlier for fertility problems than high-producing animals. Thus a negative relationship between production and fertility can always be established. In selection experiments on milk production, no adverse effects on the fertility of young animals were observed. The effects at older ages were negative, but small.