Demographic analysis of a closed Holstein Friesian herd under tropical climate

Abstract

The demographic statistics on Holstein Friesian herd of cattle maintained under tropical environment conditions were studIed. The data on 542 Holstem Friesian cattle were utilized. Demographic statistics were obtained from lifetables of.birth to age at first calving (AFC) and first till last completed lactation performance. The loss rate up to AFC was ma~lmu.m ~ron: 12 to 24 ~?nt~s age and minimum from 3 to 6 months age. The loss rate was nearly same in first 2 ~actatlO~s mdlca~Jng an equIJhbnum replacement rate of 23% for this herd. The stayability of the animals decreased wIth the Increase In age/order of lactation. The average expectancy of a cow at first lactation was 3.02 and the net reprod.uctive age was 1.56. These need to be increased to enhance the replacement rate to compensate for the loss due to culling or death. The mean rate of loss per cow per lactation was 0.28 indicating that 28% replacement heifers should be avalable for mamtammg the herd strength. It may be inferred that about 5 pregnancies of which at least 2 should be female calf bearing are required to prod,uce 1 heifer that could replace a cow by the time it is old or unproductive. Hence, for, higher reproductIve rate special care should be provided to pregnant cows and female calves born. Tilting the sex ratio In favour of females would be of immense benefit in increasing the reproductive rate.