Population structure and effect of inbreeding on lamb growth in a closed flock of bharat merino sheep

The objective of the study was to evaluate the population structure and effect of inbreeding on growth of Bharat Merino lambs. Pedigree of 8955 animals born between 1975 and 2015 was available at the farm, out of which 7803 were used for the obtaining estimates. Effective numbers of founders (fe) were 61, which represented 19.36% of founders in the population. The effective number of ancestors (fa) were 41 and the genetic contribution of the 15 most influent ancestors and explained for 50% of genetic variability. The ratio fe/fa was 1.487. The average inbreeding coefficients for the analysed pedigree and for inbred animals were 2.08% and 4.36%, respectively. The average relatedness coefficient between individuals was 4.12%. The inbreeding coefficient increased with the addition of each generation in the pedigree. The study revealed non-significant effect of individual inbreeding or increase in inbreeding with generations on the lamb weights, except weights at birth, 3 and 6 months of age where every 1% increase in inbreeding (Fi) negatively affected the birth, 3 and 6 months weight of lambs by 0.007, 0.011 and 0.006 kg, respectively. The designed mating system in the present flock is a suitable alternative to maintain the level of inbreeding under control.