Analysis of Genetic Relationship between Reproductive vs. Lamb Growth Traits in Makooei Ewes

A selection program is being implemented to improve meat production in Makooei sheep. Increasing litter size per ewe is the main objective, but possible repercussions on weight traits of lambs should be considered. The aim of this study was to estimate heritability along with genetic and phenotypic correlations between ewe's reproductive vs. weight traits in Makooei ewes. Data were comprised of 5,364 records of body weight of lambs from 289 sires and 1,726 dams, plus 3,418 records of reproductive traits from 1,429 ewes collected from 1996 to 2009 from a Makooei flock at Makoo Station in West-Azerbaijan Province. The ewe reproductive traits investigated were Conception Rate (CR), Litter Size at Birth (LSB), Litter Size at Weaning (LSW), Litter Weight at Birth (LWB) and Litter Weight at Weaning (LWW). The lamb traits investigated were Weights at Birth (BW) and at Weaning (WW). Genetic parameters were estimated through REML procedure using ASReml program. The estimates of direct heritability for lamb body weights were 0.15 +/- 0.04 at birth and 0.16 +/- 0.03 at weaning. The estimates of heritability for reproductive traits varied from 0.05 +/- 0.02 for CR to 0.17 +/- 0.03 for LWB. Additive genetic correlations between BW and ewe's reproductive traits varied from small to moderate, ranging between -0.14 and 0.22. Additive genetic correlations between WW and ewe reproduction traits varied from moderate to high, positively ranging between 0.21 and 0.67. In conclusion, WW could be considered as a selection criterion in indirectly improving the ewe's reproductive traits in Makooei sheep.