Abstract   

    Pedigree and data on 5252 birth records of 1179 Hissardale sheep during 1978-95 were utilized to evaluate the effect of inbreeding on various performance traits. Pedigree analysis revealed that there was a continuous upward trend in the average level of inbreeding in the flock. The coefficient of inbreeding among the 881 inbred animals averaged 6.91 percent, the highest level being 31.25 percent. The average value was 1.16 percent for all the animals. The total number of sires used was 159, which were 0.59 percent inbred on the average with the highest value being 12.5 percent. One of the main reasons for this low level of inbreeding in the flock was incompleteness of pedigrees especially for animals born in the earlier years of the period under study. Among the growth traits studied, birth weight, weaning weight and weights at other ages (60, 90, 180, 270 and 365 days) increased with increase in level of inbreeding but statistically this increase was not different from zero. The two growth traits, pre- and post-weaning growth rates did decrease with increase in inbreeding but again the decrease did not reach a significant level of 5%. Among the ewe traits, there was a decline in age and weight at first service as well as age and weight at first lambing with increase in the level of inbreeding. The number of services per conception also increased with rise in inbreeding level yet, the effect was not significant statistically. The effect of inbreeding on total fleece weight was also positive but non-significant.    

Key words: Hissardale sheep, inbreeding, performance traits