A meta-analysis of genetic parameter estimates for growth traits in fat-tailed sheep

Abstract

This study aimed at using a random-effects model of meta-analysis to compile the estimates of direct heritability, maternal heritability, the ratio of the permanent environmental variance to phenotypic variance, the correlation between direct and maternal genetic effects for growth traits (body weights, average daily gains, and Kleiber ratios), and also genetic correlations among these traits in fat-tailed sheep. A total of 458 direct heritability estimates, 260 maternal heritability estimates, 217 estimates of the ratio of the permanent environmental variance to phenotypic variance, 144 estimates of the correlation between direct and maternal genetic effects, and 349 genetic correlations from articles which were published between 1978 and 2021 were used in the meta-analysis. Chi-square (Q) test was performed to measure heterogeneity and the I2 statistic was determined. The average direct heritability estimates for the studied traits were low to moderate and ranged from 0.108 (for Kleiber ratio from three to six-months of age (KR3–6)) to 0.258 (for Kleiber ratio from birth to six-months of age (KR0–6)). The average maternal heritability estimates for growth traits were low and varied from 0.056 (for KR3–6) to 0.142 (for birth weight (BW)). The average correlation estimates between direct and maternal genetic effects for growth traits were negative and varied from −0.826 (for KR3–6) to −0.039 (for three-months weight (3 MW)). The genetic correlation estimates between BW and other traits were low to moderate and ranged from 0.089 (between BW-KR0–3) to 0.472 (between BW-3 MW). Also, the genetic correlation estimate between 3 MW and average daily gain from three to six-months of age (ADG3–6) was low (0.187) and not significant, but genetic correlation estimates between 3 MW and other traits were moderate to high and varied from 0.637 to 0.853 (P < 0.05). The meta-analysis showed that growth traits in fat-tailed sheep were under low to moderate genetic control. The average genetic parameter estimates obtained in this study could be utilized in the genetic selection plans for fat-tailed sheep, especially when there is limited access to accurate phenotypic records or genetic parameter estimates for the studied traits.