The aim of the current study was to estimate genetic parameters and trends
for body weight traits at different ages in Ghezel lambs. Traits included
were birth weight (BW), 3-month weight (3MW), 6-month weight (6MW), 9-month
weight (9MW), and yearling weight (YW). Data and pedigree information used in
the present study were collected at the Breeding Station of Ghezel sheep
during 1986-2009. (Co) variance components were estimated using REML
procedure and breeding values of animals were predicted with Best Linear
Unbiased Prediction (BLUP) methodology under univariate analysis. Three
different animal models were fitted. The models consisted of the direct
additive genetic effect but differed in combinations of maternal additive
genetic and maternal permanent environmental effects. Genetic trends for each
trait were obtained by regressing the means of predicted breeding values on
year of birth. The estimates of direct heritability were 0.285, 0.371, 0.388,
0.450 and 0.179, respectively. Also, the maternal heritability was estimated
0.113, 0.031, 0.021 and 0.030 for BW, WW, 6MW and 9MW, respectively. Direct
genetic trends were positive and significant for BW, WW, 6MW (p<0.01), 9MW
and YW (p<0.05) and were obtained 2.34, 46.20, 55.11, 33.40 and 24.01
(g/year), respectively. Also, maternal trends for BW, WW, 6MW and YW were
positive and highly significant (p<0.01) and were 3.37, 17.05, 12.56 and
16.30 (g/year), respectively. The results indicated that considering maternal
effects in the statistical model make accurate estimates of genetic
parameters. Also, improvement of growth traits in Ghezel sheep seems to be
likely in selection programs.
Genetic parameters and genetic trends for growth traits of the Red Maasai sheep and its crosses to Dorper sheep under extensive production system in Kenya
