Genetic analysis of body weight traits from birth to yearling in Mehraban sheep

The objective of the present study was to estimate genetic parameters and genetic and phenotypic trends of body weight traits from birth to yearling ages Mehraban sheep. Traits included were birth weight, weaning weight, 6- month weight, 9-month weight and yearling weight. The data included 10278 lambing records and pedigree information used in this research were collected at the Breeding Station of Mehraban sheep (Hamedan provice, Iran) during 1994-2011. Genetic parameters were estimated using restricted maximum likelihood procedure of the Wombat program and the SAS program was used for editing and analysising data. Direct heritabilities for BW, WW, 6MW, 9MW and YW were estimated as 0.25±0.04, 0.46±0.05, 0.59±0.08, 0.57±0.08 and 0.11±0.08, respectively. The heritability estimates of these traits suggested the most suitable trait for conducting direct selection were WW for pre-weaning and 6MW for post-weaning period. Direct genetic correlations between birth weight with other body weights ranged from -0.02 between BW and 9MW to 0.95 between 9MW and YW. Direct genetic trend was significant only for birth weight (P<0.01). Phenotypic trends were significant for all traits (P<0.01).