Effects of inbreeding on lamb survival in a flock of Muzaffarnagari sheep

A pedigree file of 4,628 records of Muzaffarnagari sheep, maintained at Central Institute for Research on Goats (CIRG), Makhdoom, was used to calculate the inbreeding coefficient of the flock. The flock had been closed for about 25 years (1978 to 2002). The investigation was aimed to study the effects of inbreeding on survivability of lambs. The cumulative survivability of lambs i.e., lambs survived up to 3, 7 and 15 days, 1, 2, 3, 6, 9 and 12 months after birth was considered for the study. The average level of inbreeding of lambs was 1.60%, ranging from 0 to 26.4%. The average inbreeding coefficient of dam over the periods was 1.00% and it ranged from 0 to 25.0%. Significant (p<0.05) adverse effect of lamb's inbreeding was observed on survivability of lambs at all ages except up to 3 and 7 days after birth. On an average, 1% increase in individual inbreeding coefficient should reduce the 0.31, 0.34, 0.32, 0.31, 0.33, 0.44 and 0.49 percent lamb survival up to the age of 15 day and 1, 2, 3, 6, 9 and 12 months, respectively. Ewes inbreeding had non-significant effects on lamb survival at all ages.