FACTORS AFFECTING SOME MILK-PRODUCTION EFFICIENCY TRAITS IN SAHIWAL CATTLE

The analysis of performance records (milk yield/ day/ lactation length and milk yield/ day/ calving interval) of Sahiwal cows maintained at 5 herds revealed significant differences among the herds. Cows in the Kamal herd were superior in MY/LL and MY/CI whereas, cows in the Hisar herd were inferior. The effect of parity, periods and seasons were also significant both on MY/LL, and MY/CI. The effect of inbreeding level on first lactation traits was nonsignificant; however, its influence on performance traits obtained by pooling data over 7 lactations was significant. Age at first calving had significant effect on MY/LL and MY/CI. The estimates of heritability of milk yield/day/first lactation length, and per day/first calving interval were low as compared to the estimates obtained from the data pooled over the lactations. The estimates of repeatability ranged from 0.42 +/- 0.10 to 0.77 +/- 0.12 and 0.42 +/- 0.11 to 0.57 +/- 0.09 for MY/LL and MY/CI, respectively, in different herds.