The role of maternal effects in sheep breeding: A review

Genetic parameters for various economic traits of sheep have been reported from time to time and there are reviews that included most of the information on estimates of heritability, repeatability and genetic and phenotypic correlations. Paternal half-sib was the model of choice for genetic analysis in the past; however recently, animal models for genetic analysis of economically important traits are frequently reported. Maternal effects contribute as a significant source of variation in early life traits of sheep, especially for growth traits. Present review summarizes estimates of maternal effects for various economic traits in Indian sheep breeds, crosses and exotic sheep breeds. Maternal effects that mostly account for the uterine environment provided by the dam along with nursing behaviour till weaning has been given due importance apart from maternal genetic effect. However, emphasis is also given on maternal genetic effect and its covariance with direct additive effect to understand the relationship and causal factors for the kind of association. This review reflects on the importance of maternal permanent environmental and genetic effects especially for growth traits followed by wool, reproduction and disease resistance traits.