The frequency of cows served twice which remain pregnant to first service: a study of results from parentage tests

Abstract

In 1,347 parentage cases in cattle it was determined whether conception resulted from the first or second service. Among cows served twice within short intervals (1–11 days) about 20% remained pregnant from the previous service. At an interval of one day this proportion amounted to 37%.About three-quarters of the cows had service intervals of 18–24 days. In most of these the calving took place between the expected dates according to the two services. In 6% of the cases with intervals of 18–24 days pregnancy resulted from the first service. It was estimated that about 1% of all cows mated twice within these intervals had become pregnant from the first service.Rules are suggested for when blood grouping should be required for registration of pedigrees in the herd book.