Genetic factors affecting performance traits of Sahiwal cattle in Pakistan

Data on 23925 lactations of 5897 Sahiwal cows in five Government herds of Punjab province were collected to estimate the genetic control and genetic correlations among performance traits. A repeatability animal model having herd-year-season and parity was used for this purpose. The repeatability estimates for 305-d milk yield, total milk yield, lactation length, dry period, calving interval and service period were 0.40 plus minus 0.015, 0.40 plus minus 0.016, 0.33 plus minus 0.013, 0.14 plus minus 0.005, 0.15 plus minus 0.004, and 0.14 plus minus 0.005 respectively. The heritability estimates for these traits were 0.10 plus minus 0.016, 0.09 plus minus 0.016, 0.06 plus minus 0.013, 0.14 plus minus 0.009, 0.15 plus minus 0.010, and 0.14 plus minus 0.010, respectively. The phenotypic, genetic and environmental correlation of 305-d milk yield with lactation length was 0.71, 0.48 and 0.70, respectively, with dry period was -0.31, -0.43 and -0.22, respectively while with calving interval and service period exhibited similar pattern (0.08, 0.25 and 0.08, respectively). The estimated breeding values ranged from -447 to 1254 kg, -442 to 1265 kg, -24 to 38, -78 to 116, -84 to 107 and -81 to 91, days for 305-day milk yield, total milk yield, lactation length, dry period, calving interval and service period, respectively. No specific genetic trend was observed for performance traits during the period under study. Cows have not improved in their ability to perform in various economic traits. Accurate recording of pedigree and performance is necessary for improving the performance traits of Sahiwal. Due to high repeatability estimates of yield traits selection or culling may be practiced from first few records.