Estimation of genetic parameter for average daily gains and Kleiber ratios in Makooei Sheep

Mutton production in Iran, as the main source of red meat, does not satisfy the increasing demand of the consumers. Estimation of genetic parameters of economic important traits are necessary for determining breeding goal and selection index. In this study, data were collected from 1996 to 2014 at the Makooei Sheep Breeding Station (Makoo) in west-Azerbaijan province were used to estimate the genetic parameters for growth traits and Kleiber ratios. Traits studied were birth weight (BW), weaning weight (WW), six month weight (6MW) and yearling weight (YW), Average daily gain from birth to weaning (ADGa), Average daily gain from weaning to six months of age (ADGb), Kleiber ratio from birth to weaning (KRa), and Kleiber ratio from weaning to six months of age (KRb). (Co) variance components were obtained fitting different animal models using a restricted maximum likelihood (REML) procedure via ASREML program. The most appropriate model for each trait was determined based on log likelihood ratio tests. The most appropriate model for birth weight trait model 3 (direct and maternal genetic effects, without considering covariance between them), weaning weight, six month weight and Average daily gain from birth to weaning Model 2 (direct additive genetic effects and maternal permanent environment) and yearling weight, Average daily gain from weaning to six months, Kleiber ratio from birth to weaning, and Kleiber ratio from weaning to six months of age Model 1 (direct effects). Direct estimate of heritability for BW, WW, 6MW, YW, ADGa, ADGb, KRa and KRb was 0.15±0.04, 0.16±0.03, 0.21±0.04, 0.22±0.06, 0.13±0.05, 0.14±.04, 0.06±0.03 and 0.03±0.02, respectively. The estimate of maternal heritability for BW was 0.08±0.02. Genetic correlations were ranged 0.13 (between YW with KRb) to 0.94 (between WW with KRa). The results of this study indicated that selection for Kleiber ratio can result in genetic improvement of growth rate as well as feed efficiency.Genetic parameter estimates of local breeds are important. Genetic parameter estimates of local breeds are important for conservation purposes, defining breeding objectives, and programs. The traits having economic value such as growth
rate and Kleiber ratio are influenced by individual direct genetic, maternal effects, and environment which animal is raised Profitability of a sheep production system can be influenced by growth rate of the lambs in different ages. Normally, the lambs having more growth rate are more capable of reaching market weight. Growth rate is defined as the average daily gain of an individual in a specific period and can be classified as from birth to weaning, from birth to 6 months of age, from weaning to 6 months of age