Investigation of direct and maternal genetic effects on birth and weaning weight of Chios lambs

Abstract

Direct additive and maternal genetic effects on birth and weaning weight of Chios lambs were investigated. The data originated from the Agricultural Research Station of Chalkidiki and comprised 7318 lambs, raised over the period from 1977 to 1992. Variance components were estimated using restricted maximum likelihood, fitting six different animal models, by including or excluding maternal effects. The direct heritability ( h 2 d ) for birth weight decreased from 0.38 to 0.13 when maternal genetic effects were included in the model, while h 2 d for weaning weight decreased from 0.29 to 0.15. The maternal heritability ( m 2) for birth weight was 0.33 when only maternal genetic effects were included in the model and ranged from 0.13 to 0.19 when the permanent environment of the dam ( c 2) was added. The respective values of m 2 for weaning weight ranged from 0.14 to 0.16 and 0.05 to 0.07. The permanent environmental effect of the dam was significant for both traits. Negative genetic covariance between direct and maternal genetic effects ( σ am ) was observed, which was significant only for birth weight.