Estimation of maternal covariance components for growth traits in the Sahiwal cattle

Abstract

Maternal influence on growth of artificially reared Sahiwal cattle was investigated using data from the National Sahiwal Stud (NSS). Growth records on animals born from 1973 to 2004 were used for the analysis. The traits considered were; birth weight (BW, kg), weaning age at 42kg weight (WA1, days), weaning age at 55 kg weight (WA2, days), weaning age of all animals weaned at 42 kg and 55 kg combined (WA, days), branding age at 130 kg (BA, days), preweaning daily gain to WA1 (DG1, g/day), preweaning daily gain to WA2 (DG2, g/day), preweaning gain from combined data (DG, g/day), post weaning daily gain to BA (PDG, g/day) and average daily gain from birth to BA (ADG, g/day). Maternal effects were important for BW but low to almost absent for pre- and post weaning traits. Ignoring maternal effects substantially increased the direct additive genetic variance and hence direct heritability estimates. Fitting maternal effects reduced direct heritability from 0.34 to 0.15 for BW. Genetic correlations between direct and maternal effects were positive and high for BW (0.66 and 0.72). The low and absence of maternal effects on pre- and post weaning traits shows that improvement in these traits would be more efficiently achieved if selection was based on the animal’s direct genetic potential. The influence of maternal effects on BW of artificially reared Sahiwal cattle indicates that inclusion of these effects in analysis of BW will result in accurate parameter estimates which would improve selection efficiency.