Calving performance and calf mortality

Abstract

The most important maternal factor influencing calving performance is parity. Among calf factors, birth weight seems the most important. There are large differences between breeds and, generally speaking, heavier beef and dual-purpose breeds present more problems than smaller cattle. Variation in calving performance and stillbirth may be attributed to characters of both the calf and the dam. Genetic variation in calving performance and stillbirth at first calving has been demonstrated in several investigations for both the direct (calf) and the maternal character. In a Swedish investigation a heritability of 10% was found for both the direct and the maternal character. For stillbirth values were on average 3%. A strong genetic relationship was found between calving performance and birth weight as direct characters ( r G D = 0.98) but for the maternal characters it was considerably weaker ( r G M = 0.60). Correlations between stillbirth rate and birth weight were generally weaker, because the relationship was non-linear. Estimations of the genetic correlations between direct and maternal effects gave values between zero and −0.5 for the characters investigated, indicating an antagonistic relationship between the genetic make-up of the cow and the calf. This implies that, in the long run, selection will not be as effective as the heritabilities suggest. A substantial improvement in calving performance and calf mortality can be achieved, however, through selection within breeds, optimal organization of breeding structures, choice of appropriate beef breeds for cross-breeding on heifers and cows, respectively, and timing calving to occur at favourable ages and in favourable seasons.