Meta-analysis of genetic parameters for growth traits in Iranian sheep

Meta-analysis of genetic parameters for growth traits in Iranian sheep was performed by aggregating the reported genetic parameters of growth traits (birth weight, weaning weight, six months weight, nine months weight and yearling weight) in 80 papers published between 1996 and 2020. The studied parameters consisted of heritability values as well as genetic and phenotypic correlations between growth traits at different ages. Data analysis was performed in Comprehensive Meta-Analysis (Version2) software package using random effects model. The weighted average of heritability for growth traits was estimated in the range of 0.196 (birth weight) to 0.226 (yearling weight) and the weighted averages of genetic and phenotypic correlations were in the range of 0.318-0.915 and 0.221-0.769, respectively. Comparison of 95% confidence interval for genetic parameters obtained from meta-analyses with those mentioned in articles showed that aggregation of the results of different studies had significantly reduced the confidence interval ranges. Moreover, comparison of standard error of parameters in meta-analyses with those in different studies showed that the aggregation of results and subsequent increase in sample size reduced the standard errors of the genetic parameters. Therefore, comparing the results of meta-analysis in this study with the estimated parameters in individual studies showed that aggregation of results decreased the standard error and increased the accuracy of estimated parameters. Consequently, the results of meta-analysis studies can be more reliable compared to the results of individual studies to be used in breeding programs.