Environmental factors affecting performance traits of crossbred and local dairy cows at Mirpur Azad Jammu and Kashmir

Data on about 3999 records from 1990 to 2003 collected at artificial insemination center Mirpur city were utilized for this study and analyzed using Harvey's Mixed Model Least Squares and Maximum Likelihood Computer Program to study the environmental sources of variation on some performance traits of Desi /local, F1 (Holstein Friesian and Jersey X Desi), Holstein Friesian, Jersey and Sahiwal dairy cows of different genotype. The least squares means for number of services per conception, age at first service and gestation period were 1.07 plus minus 0.18, 990.37 plus minus 239.24 days and 280.84 plus minus 0.35 days, respectively. The coefficient of variation for these traits was 24.31, 21.97 and 1.71 percent respectively. The least squares means for daily milk yield was 8.72 plus minus 0.18 liters with 32.42% coefficient of variation. The analysis of variance for age at first service revealed that year and genotype showed significant differences (P less than 0.05), however, the season of birth had non-significant effect on age at first service. Moreover, data revealed that the year of service and genotype have significant (P less than 0.01) influence on number of services per conception during the study period, however, the season of service and parity showed non-significant difference. There was no significant difference due to age at service of the cows. The difference was non- significant in the number of services per conception due to increase in the age of cow. It was further observed that the gestation period in the present data set was significantly (P less than 0.05) different due to year/ season of birth, genotype, parity and sex of the calf born. The variability in daily milk yield was significant (P less than 0.05) due to year of calving and genotype of animal, whereas, there was non significant difference in daily milk yield due to increase in the age of animal. The conception rate was variable in different year, season, genotype and parties. The mean conception rate during different season was 55.71 percent. It was the highest (79.63 %) during summer and lowest on autumn (43.40 %). Conception rate was 62.55, 61.55, 58.33, 58.14 and 59.07 percent, respectively in Desi, F1, Holstein Friesian, Jersey and Sahiwal cows. The calving rate was 70.55 percent of the pregnant cows. It varies in different seasons of the year ranging from 53.804 percent in summer to 91.73 percent in spring. The calving rate was higher in Holstein-Friesian (74.36 %) and lowest (60.00 %) in Sahiwal. It was 69.29 percent and 69.45 percent in Desi and F1 (crossbred), respectively.