Effect of Inbreeding Coefficient on Growth and Fitness Traits in a Closed Flock of Corriedale Sheep

Background: The corriedale sheep breed was imported into J and K during sixties for use in improvement of local sheep and are maintained at Mountain Research Station of Sheep and Goat, SKUAST- K. The animals over the years were allowed to mate within the selected animals of the flock as there was hardy any fresh importation of exotic animals from last 49 years due to which closed flock population was established within the farm. This has led to apprehensions over the loss of genetic diversity through years. Methods: The present study was to undertaken to evaluate the performance of Corriedale sheep under temperate climate and to estimate the inbreeding coefficient and its effect on growth and fitness traits of Corriedale sheep maintained at Mountain Research Centre for Sheep and Goat (MRCSG), F.V.Sc and A.H, SKUAST-K Shuhama, Kashmir. The information on performance and pedigree spanning over a period of 49 years (1969-2017) was collected and utilized for the study. The traits studied were birth weight (BW), weaning weight (WW), 6 months weight (6MW), 9 months weight (9MW) and 12 months weight (12MW) age at first lambing (AFL), litter size (LS), total lambs born per ewe (TLB) and survival rate (SR). Result: The averages estimates for BW, WW, 6MW, 9MW, 12MW, AFL, LS, TLB and SR were 3.72 +/- 0.01 kg, 13.31 +/- 0.07 kg, 18.65 +/- 0.05 kg, 22.15 +/- 0.04 kg, 25.84 +/- 0.06 kg 807.20 +/- 4.34 days, 1.08 +/- 0.00, 4.83 +/- 0.03 and 80.76 +/- 1.98, respectively. The overall inbreeding coefficient ( F) and proportion of population inbred (per cent) for Corriedale sheep were 18.3 and 43.3, respectively. The increased inbreeding coefficient had negative impact and highly significant (p<0.01) on all the traits under study except LS. The increased inbreeding coefficient (F) also had a negative impact on all the traits under study. With increase in the level of inbreeding there was a decrease in total body weight traits, lambs born per ewe and survival rate where as age at first lambing was increasing with the increase. he results indicated as decrease of 0.25 kg, 1.45 kg, 5.04 kg, 5.53 kg and 5.48 kg in body weight of the animals at birth, weaning weight, six months, nine months and twelve months from 1969-2017. To overcome the negative impact of inbreeding coefficient in the flock introduction of genetic variability through importation of Corriedale germplasm into the farm is highly recommended.