An evaluation of maternal influences on growth traits: The Zandi sheep breed of Iran as an example

Abstract

An animal model was used to estimate direct and maternal genetic parameters for birth weight (BW), weaning weight (WW), 9-month weight (W9) and yearling weight (YW) for a population of Zandi sheep. The magnitude of estimates of these parameters was used to evaluate the importance of direct and maternal influences on body weight at various stages of Zandi lambs' life. Results confirmed the potential maternal influences to change pattern of body weight's heritability with age. Maternal influences were significant for early growth traits. The importance of maternal influences diminished with age, although for W9 and YW those effects did not disappear completely. In contrast to variation due to maternal effects, the variance of direct effects increased from birth to a year of age. Estimates of maternal breeding values averaged by year of birth decreased throughout the experiment for both BW and WW. It was concluded that for more precise designing selection programs and, in consequence, increasing efficiency of selection, inclusion of maternal effects as well as direct-maternal genetic covariance into the model, especially for early growth traits, is necessary.