Age at first calving and factors influencing it in dairy heifers kept by smallholder farmers in Southern Malawi

摘要

Delayed age at first calving (AFC) is known to decrease productivity in dairy cattle. In the present study, we investigated AFC in heifers kept by smallholder farmers in southern Malawi and the reproductive factors influencing it. Data were obtained for 1,620 heifers over a 13-year period from 1999 to 2012. The age at first service (AFS), first service to conception interval (FSCoI), number of services per conception (NSC), conception rate (CR) and service interval (SI) were investigated in relation to AFC. The median AFC was found to be 41 months. This is a relatively high value and shows no improvement from the values reported in the 1970s and 1980s. The median AFS was also high (23 months). Overall, the 1st service CR was 42%, and the median SI was 83 days. AFS appeared to be the most crucial factor that affected AFC. A lengthy SI in combination with a low CR was found to be the critical factor that delayed AFC in heifers that had failed to conceive on previous occasions. These results suggest that the appropriate reproductive management of heifers, particularly initiating the first service at the optimum time and shortening the SI, is necessary for improving dairy productivity.