Abstract
The data on 112 lactation records of Sahiwal cows kept at the Livestock Experiment Station, Khizarahad were analysed to study the effect of weight at first
calving on first lactation performance. The weight at first calving, first lactation 305-
days milk yield and milk yield per day of lactation averaged 353.95 ± 3.84, 1896.03 ±
34.83 and 6.53 ± 0.12 kg, respectively. The postpartum oestrus interval, service
period and number of services per conception on an average were 160.04 ± 7.72,
216.86 ± 11.26 days and 2.13 ± 0.15, respectively. The correlation coefficient between weight at first calving and first lactation 305-days milk yield, milk yield per
day of lactation, postpartum oestrus interval, service period and number of services
per conception were 0.047, 0.226, -0.289, -0.261 and 0.035, respectively. Similarly, the
regression coefficients were 0.430 ± 0.865, 0.008 ± 0.0<)3, -0.582 ± 0.184, -0.765 ±
0.270 and 0.001 ± 0.004, respectively.
