مشخصات پژوهش

Genetic parameters for growth traits and Kleiber ratio were estimated in Sanjabi sheep. Data collected from 1992 to 2002 in Mehregan Breeding Station in Kermanshah province at west of Iran were analyzed. Studied traits were birth weight (BW), weaning weight (WW), sixmonth weight (6MW), nine-month weight (9MW), yearling weight (YW), average daily gain from birth to weaning (ADG1), Kleiber ratio from birth to weaning (KR1), average daily gain from weaning to six months of age (ADG2) and Kleiber ratio from weaning to six months of age (KR2). (Co)variance components were obtained fitting different animal models using restricted maximum likelihood (REML) procedure. Akaike information criterion (AIC) was applied to determine the most appropriate model for each trait. Model including maternal genetic effects as well as direct genetic effects, without considering covariance between them, was chosen as the most appropriate model for BW, ADG1 and WW. For KR1 and 6MWthe model including permanent environmental effects due to ewe over direct genetic effects was the most appropriate one. Model which included only direct genetic effects was the most suitable model for other traits (9MW, YW, ADG2 and KR2). Direct heritability estimates of 0.09, 0.15, 0.09, 0.19, 0.11, 0.14, 0.08, 0.15 and 0.07 were obtained for BW,WW, 6MW, 9MW, YW, ADG1, ADG2, KR1 and KR2, respectively. Maternal heritabilities for BW, ADG1 and WW were estimated as 0.14, 0.23 and 0.24, respectively. Ratios of phenotypic variance due to maternal permanent environmental effects were 0.11, 0.21 and 0.16 in respective order for BW, KR1 and 6MW. Estimates of direct genetic correlation among studied traits were very low to high in magnitude and varied from −0.00 for BW–KR2 to 0.99 for WW–6MW, ADG1–YW and ADG2–9MW.