Factors affecting milk production and reproductive performance of Jersey crossbred heifers.

摘要

The aim of this study was to investigate the effects of age at first calving, dry period, service period and calving interval on the milk production and reproductive performance of first calved crossbred heifers (Jersey x Tharparkar, JT). A total of 824 records of variables of JT heifers were collected for 8 years (2001-07). The data for total milk yield (TMY), 305 days milk yield, lactation length (LL), number of AI, weight at first calving (WFC), birth weight, age at first calving (AFC), service period (SP), dry period (DP) and inter-calving period (ICP) were collected. The AFC varied significantly between heifers (P<0.01). No effect of AFC was observed on the birth weight, SP, LL, DP, TMY and 305 days milk yield. However, the number of AI varied significantly (P<0.01) in heifers at different AFC. The body weight of heifers at different AFC varied significantly (P<0.01). The calf weight and AFC were positively correlated (P<0.05) with the body weight at first calving. The TMY and 305 days milk yield were significantly different between the groups (P<0.05). The service period did not influence the birth weight, DP and body weight at first calving. LL and ICP were greater (P<0.01) in heifers which had a service period of >250 days, leading to more TMY and 305 days milk yield (P<0.01). The SP was positively correlated to the TMY and 305 days milk yield (P<0.05). The TMY was significantly more (P<0.05) and ICP was less (P<0.01) in heifers of normal group (2527.49+or-41.43 kg) than in heifers of the higher group (1815.77+or-201.75 kg). However, the effect of DP on 305 days milk yield, number of AI, birth weight, WFC and LL was insignificant. The DP was positively correlated with LL (P<0.01) and negatively correlated with TMY (P<0.05). The ICP significantly affected (P<0.05) the TMY and 305 days milk yield. No effect of ICP was observed on the DP, birth weight and AFC. The ICP was positively correlated (P<0.01) with DP, LL and SP.