[Relationship between heterozygosity as estimated from genetic markers and fertility in cattle : II. Heterozygosity and fertility].

The present investigation deals with the connexion between heterozygosity, as estimated from markers, and fertility traits in cattle. In adult cows and/or cows under suboptimal management the maternal marker heterozygosity showed a definite influence upon fertility. In unselected field records of the Hinterwälder breed, the calving interval decreased 2.3 days per 10% increase in marker heterozygosity. The number of inseminations per conception decreased by 6.2% per 10% marker heterozygosity in Fleckvieh progeny groups. Cows with less than 20 and 25%, resp., marker heterozygosity differed from those with more than 50 and 55%, resp., by 11.1 days calving interval and 0.6 inseminations per conception, resp. It was not found that the estimated marker heterozygosity of the prospective foetus influenced the success of the insemination. This might be due to the rather imprecise method of estimating foetal marker heterozygosity, but other investigators also attribute less importance to foetal heterozygosity than to maternal heterozygosity. Fertility traits of cattle are essentially all-or-none characters. Therefore, the lack of statistical significance of some of the results presented here may be due more to the imprecision of the estimate of fertility of the relatively small groups than to the method used.