Environmental Factors Affecting Performance Traits of Sahiwal Cattle in Pakistan

Data on 23925 lactations of 5897 Sahiwal cows in five Government herds of Punjab (Pakistan) viz. Livestock Experiment Station (LES) Allahdad, LES Bahadurnagar, LES Fazalpur, LES Jahangirabad and LES Khizerabad (1964-2004) were collected to document the behavior of various productive and reproductive traits of Sahiwal cows with respect to herd, year and season of calving and parity. A linear model was used to determine the effects of various environmental factors on performance traits. The 305-day milk yield, total milk yield, lactation length, dry period, calving interval and service period averaged 1530.5±12.36 kg, 1552.1±12.15 kg, 235±1.4 days, 218±2.1 days, 438±2.7 days and 151±2.8 days, respectively. All the productive and reproductive traits were affected (P 0.01) by herd, year, season of calving and parity. Lactation length was important covariable for yield traits while yield was important for dry period, service period and calving interval. Maximum yield was recorded for 5^th parity cows. Calving interval differed by two months among herds. Cows calving in most frequent calving season (winter) produced more milk than summer calvers (1608.6±12.91 kg vs 1474.1±13.63 kg). The phenotypic trends for 305-day milk yield, total milk yield, lactation length, dry period, calving interval and service period were -1.33 kg, -0.21 kg, -1.27 days, +1.52 days, +0.32 days and +0.59 days, respectively. Lactation length (244.5 days) was used as covariable. Improvement in feeding and breeding management and culling on productivity may improve the performance of Sahiwal cows.