META-ANALYSIS OF THE POSITIVE EFFECT OF GINGER FEED ADDITIVE ON HEALTH AND PRODUCTION INDICES OF LAYING HENS

Meta-analysis of the effects of ginger (Zingiber officinale) supplementation on outcome measures (health and production indices) in laying hens was investigated. A database of eighteen studies on the subject was systematically compiled based on set inclusion criteria and were used for the analysis. Outcome measures were pooled using a random-effects model and quantified using standardised mean difference (SMD) at 95% confidence interval (CI). The pooled results indicate that ginger supplementation improved blood antioxidant markers in laying hens. The results also showed that layers on ginger supplementation had significantly better plasma cholesterol concentrations (SMD =-1.140 mg/dl, 95% CI:-1.622 to-0.658) and hen day egg production (SMD = 0.217%, 95% CI: 0.080 to 0.354) compared to the controls. In addition, layers on ginger supplementation had significantly higher egg mass (SMD = 0.245 g egg/hen/day, 95% CI: 0.017 to 0.473) and egg weight (SMD = 0.096 g, 95% CI: 0.029 to 0.163) when compared to the controls, taking cognizance of heterogeneity. Meta-regression found that studied moderators explained most of the sources of variation. This meta-analysis suggests that ginger could improve health indices, hen day egg production, egg mass and egg weight in laying hens.