Meta-analysis of zinc feed additive on enhancement of semen quality, fertility and hatchability performance in breeder chickens

Abstract

Abstract The incorporation of zinc in the diets of breeding chickens to enhance reproductive performance has been highlighted. However, no consensus has been reached on the effect of dietary zinc supplementation on the reproductive outcomes of breeding chickens. Therefore, the current study assessed the effects of dietary zinc supplementation on semen quality, fertility and hatchability percentage of breeding chickens using meta-analysis. Furthermore, subgroup analysis was also used to assess the effect of zinc sources (organic versus inorganic) on the reproductive outcomes of breeding chickens. A systematic search conducted on four electronic databases following the Preferred Reporting Items for Systematic Reviews and Meta-analyses yielded 521 candidate studies; 8 of the 521 studies that examined the effects of zinc supplementation on reproductive outcomes of breeding chickens met the selection criteria and were used for the meta-analysis. Outcome measures were pooled using random-effects model and expressed as standardized mean difference (SMD) at a 95% confidence interval (CI) for each study. OpenMEE software was used for the analysis. The results indicate significant increase in semen output (SMD = 1.32 mL, 95% CI: 0.76, 1.89), sperm motility (SMD = 1.10 %, 95% CI: 0.81, 1.39), sperm concentration (SMD = 4.28 × 106/mL, 95% CI: 2.78, 5.79), live sperm percent (SMD = 0.96%, 95% CI: 0.69, 1.23) and significant reductions in percentage dead sperm (SMD = –2.80%; 95% CI: –3.43, –2.17), and abnormal sperm (SMD = –4.64%; 95% CI: –5.74, –3.53) when compared to controls, taking cognizance of heterogeneity. In contrast, zinc supplementation had no effect on fertility and hatchability percentage. The subgroup analysis results revealed that zinc sources influenced aspects of the reproductive outcomes of breeding chickens. We conclude that dietary zinc supplementation had a positive influence on reproductive outcomes of breeding chickens, but did not affect percentage fertility and hatchability.