Performance of kajli sheep in Pakistan. B. Fertility and lamb production as influenced by environment

Data on 16470 birth records of 5311 Kajli ewes maintained at two Livestock Experiment Stations (Khushab, 1977-94 and Khizarabad.1980-94) were utilized in the present study. The data were analyzed by using Harvey's Mixed Model Least Squares and Maximum Likelihood computer program. The objective was to evaluate the reproductive performance of Kajli sheep in Pakistan. An effort was made to estimate the extent of different environmental and genetic sources of variation influencing various reproductive traits of economic importance. Fertility was 88 plus minus 1 percent and the data revealed that year of lambing and age of ewe had a significant (P less than 0.01) effect on fertility. The litter size at birth and weaning were 1.16 plus minus 0.003 and 1.12 plus minus 0.003, respectively. The data revealed that station, year and season of lambing and age of ewe were significant (P less than 0.01) sources of variation for litter size at birth, whereas, station was non-significant for litter size at weaning. The regression of litter size at birth on breeding weight was also significant (P less than 0.01). The annual number of lambs born and weaned per ewe in different age groups was 1.11 plus minus 0.01 and 0.95 plus minus 0.01. The flock size varied from 845 ewes to 2088 ewes with mean value of 1457 ewes. However, the mean annual replacement rate was 24.04% in both the flocks. About 31% ewes were replaced just after their first parturition i.e. longevity group 1 and continued to decrease longevity group 6. Ewe longevity group 4-6 was the most productive with respect to practical flock maintenance and net output. The ewes showed an additive increase for number of lambs born and weaned with increase of the ewe age.