The influence of zinc oxide utilization in ruminants: A systematic review and meta-analysis.
ZnO supplementation can significantly improve methane production and dry matter digestibility in ruminants, but the practical implications may vary based on specific conditions.
Where it sits
this study against the rest of the ghrp-6 corpusSummary and findings
This meta-analysis evaluated the effects of zinc oxide (ZnO) supplementation on rumen fermentation characteristics and productive performance in ruminants using 17 studies. ZnO supplementation significantly improved several parameters, including reducing methane production and increasing dry matter digestibility. The findings suggest that ZnO could enhance productivity in ruminant feeding systems.
Abstract
Zinc (Zn) is an essential trace mineral involved in rumen microbial activity, nutrient metabolism, and animal productivity. This meta-analysis quantitatively evaluated the effects of ZnO supplementation on rumen fermentation characteristics, nutrient utilization, and productive performance in ruminants using 17 eligible studies published between 1971 and 2025. Standardized mean differences (SMD) were pooled using random-effects models. Heterogeneity was assessed using <i>I</i>² statistics, while subgroup analysis were performed according to ZnO form. Publication bias was evaluated using funnel plot inspection, Egger's regression test, and trim-and-fill correction. ZnO supplementation significantly improved several <i>in vitro</i> fermentation parameters by reducing methane production (SMD = -1.281; 95% CI: -1.818 to -0.743; P < 0.001), increasing propionate concentration (SMD = 0.521; P = 0.026), decreasing the acetate-to-propionate ratio (SMD = -1.226; P < 0.001), and increasing metabolizable energy (SMD = 2.034; P < 0.001). <i>In vivo</i>, ZnO supplementation reduced ruminal ammonia concentration (SMD = -0.869; P < 0.001) while increasing total volatile fatty acids (SMD = 0.520; P = 0.018), dry matter digestibility (SMD = 9.944; P < 0.001), average daily gain (SMD = 0.565; P = 0.004), dry matter intake (SMD = 0.649; P = 0.020), and alkaline phosphatase activity (SMD = 0.822; P = 0.033). Subgroup analysis revealed that nZnO consistently produced larger effect sizes for methane mitigation and growth responses than ZnO. Although publication bias was detected for methane outcomes, trim-and-fill analysis confirmed the robustness of the antimethanogenic effect (adjusted SMD = -1.082; P < 0.001). These findings provide quantitative evidence supporting that the supplementation of ZnO is a feasible option to improve productivity and sustainability in ruminant feeding systems.