Estimation of genetic parameters for body weight at different ages in Mehraban sheep
The objective of the present study is to estimate genetic parameters of birth weight (BW, n = 3005), weaning weight (WW, n = 2800), 6 months weight (6 MW, n = 2600), 9 months weight (9 MW, n = 1990) and yearling weight (YW, n = 1450) of Mehraban sheep, collected during 1995 - 2007 at Mehraban sheep Breeding Station in Hamedan province, Iran. (Co)variance components and genetic parameters were estimated with univariate and multivariate animal model using restricted maximum likelihood (REML) procedure. Effect of herd, lamb's sex, and year of birth were significant on all traits (P < 0.05). The estimates of direct heritability for BW, WW, 6MW, 9MW and YW were 0.30±0.05, 0.30±0.04, 0.35±0.05, 0.37±0.04 and 0.43±0.04 respectively. Maternal heritability estimates for mentioned traits were 0.17±0.03, 0.18±0.03, 0.14±0.03, 0.12±0.03 and 0.10±0.02, respectively. The estimates of the direct genetic correlation between BW-WW, BW-6MW, BW-9MW, BW-YW, WW-6MW, WW-9MW, WW-YW, 6MW-9MW, 6MW-YW and 9MW-YW were 0.287±0.09, 0.305±0.09, 0.249±0.03, 0.136±0.07, 0.825±0.34, 0.713±0.05, 0.845±0.52, 0.862±0.06, 0.596±0.09 and 0.712±0.02 respectively. The estimates of the phenotypic correlation between traits were positive and ranged from 0.152 for BW-9MW to 0.835 for 9MW-YW.
Key words: Mehraban sheep, heritability, genetic correlation, body weight traits.