Dietary Supplements Improve the Growth Performance and Carcass Yields of Indigenous Sheep in Ethiopia: A Systematic Review and Meta-Analysis Study

Despite the large number of sheep in Ethiopia, their productivity remains low, mainly due to inadequate and poor-quality feed. Therefore, this systematic review and meta-analysis study was conducted to evaluate the effect of dietary supplements on the growth performance and carcass yield indices of indigenous sheep in Ethiopia. This study included a total of 21 studies that used 533 sheep from 11 breeds. We used Meta-Essentials Version 1.5 to determine the effect sizes in a mixed-effects model at p < 0.05. The current meta-analyses revealed that dietary supplements had a positive and significant effect (p of Z ≤ 0.001) on the total dry matter intake (Hedges' g = 6.84 g/day/head), final body weight (Hedges' g = 3.65 kg/head), average daily gain (Hedges' g = 3.59 g/head), feed conversion efficiency (Hedges' g = 0.72 g/g), slaughter weight (Hedges' g = 2.56 kg/head) and hot carcass (Hedges' g = 2.73 kg/head) of sheep compared to the control. The meta-analysis suggests that sheep of different breeds and sexes that were fed supplemental diets responded differently. In addition, the subgroup analysis declared that dietary supplementation of legumes resulted in a higher magnitude of effect sizes for all response variables in sheep in comparison to sheep supplemented with concentrate and browse. We detected diverse heterogeneity across studies for all response variables that ranged between 0% and 96.65%. It can be concluded that dietary supplements had a positive and significant impact on feed efficiency, growth performance and carcass yield in indigenous sheep, particularly Afar sheep, followed by Arsi Bale and Washera sheep, in Ethiopia.