GENETICS OF REPLACEMENT RATE IN A HERD OF THARPARKAR CATTLE

摘要

Based on 4774 pregnancies settled from 1368 Tharparkar cows for a period of 59 years, it was found that only 1422 pregnencies amounting to 29.8 percent were turned into replacement heifers and rest of them were lost:4.4 percent as abnormal calves, 49.1 percent as male calves and 16.7 percent as death (9.8%)and culling (6.9%) of female calves. Thus on an average, about 3-4 pregnencies are required to produce one replacement heifer. Out of 2222 female calves born only 64.0 percent survived to the age at first calving and rest were died (21.1%) and culled (14.9%). Period of birth had highly significant effect on replacement rates on both the basis while the season of birth and dam's parity had no effect on replecement on either basis. The effects of generations and sires were highly significant on replacement rate on both the basis but the heritability estimates were found to be low.