Abstract
Data on 9080 records of Thalli sheep maintained at Livestock Experiment Station, Rakh Ghulaman Distt. Bhakkar
during the period of 1975-2004 were utilized in the present study. Average values for 180, 270 days, yearling and
post-weaning average daily gain were 22.37±4.21, 25.96±4.90, 28.93±5.20 and 0.028±0.02 kg, respectively.
Effect of inbreeding on post weaning growth traits was studied by analysis of variance technique and by
regression method. Level of inbreeding ranged from 10.15 to 37.50 percent with the mean value of 1.70 percent
of population. Inbreeding significantly (P<0.05) affected weight at 270 days of age, yearling weight and postweaning average daily gain. Weight at 270 days of age, yearling weight and post-weaning average daily gain
decreased 0.013, 0.019 and 0.098 kg as 1 percent increase in the level of inbreeding. Inbreeding had nonsignificant effect on weight at 180 days of age. Regression value for trait was 0.093. The net effect of inbreeding
in a selection programme will depend on the magnitude of the selection response relative to the depression due
to the accumulated inbreeding. Depending on whether genetic gain and inbreeding depression compensate for
each other or the level of inbreeding of the animals, may need to be accounted for in the selection process.
Key words: Sheep, Inbreeding, post-weaning, growth.
