Estimation of genetic parameters for pre-weaning growth traits in Central Anatolian Merino sheep

Quantitative traits such as pre-weaning growth is expressed as a result of combined genetic and environmental effects. The phenotypic expression of those traits in offspring is affected by direct genetic effect and sometimes also maternal genetic effect which is the ability of the dam to provide optimum nurturing conditions. The objective of the current study was to estimate genetic parameters for birth weight (BW), weaning weight (WW) and average pre-weaning daily weight gain (ADWG) in Central Anatolian Merino sheep. Observations of 9746 lambs descending from 171 rams and 2045 dams between 2014 and 2020 were included in the study. Generalized linear models were applied to determine the best fitting fixed effects model. Subsequently, the estimations of variance and covariance components were carried out by using the restricted maximum likelihood (REML) procedure applied on an animal linear mixed model including those significant effects on preceding analyses. In general, the direct heritability estimates of the traits were moderate for BW, WW and ADWG as found to be 0.22 ? 0.02, 0.32 ? 0.02 and 0.33 ? 0.02 respectively. On the other hand, maternal heritability estimates were considerably low for all traits with 0.04 ? 0.01 (BW), 0.03 ? 0.01 (WW) and 0.03 ? 0.01 (ADWG). The genetic correlations between BW and WW was moderate and negative as -0.30 ? 0.05 whereas, the phenotypic and residual correlations were close to zero. Similarly, the correlations between BW and ADWG were negative for all type of correlations. Especially, a moderate genetic correlation was found between the two traits as -0.37 ? 0.05. As expected, the correlations between WW and ADWG were quite high and positive for all type of correlations. The outcomes of the study will contribute to the world-wide sheep breeding literature with the crossbred performance of Merino and an indigenous sheep breed, as well as its parameters of interest in terms of designing breeding programmes with multi-trait selection indices.

Automated summary

This study estimated genetic parameters for birth weight (BW), weaning weight (WW), and average pre-weaning daily weight gain (ADWG) in Central Anatolian Merino sheep. The results showed moderate direct heritability estimates for BW, WW, and ADWG, while maternal heritability estimates were relatively low. The genetic correlation between BW and WW was moderate and negative, while phenotypic and residual correlations were close to zero.