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.