Meta-analysis of the effect of probiotic-yeast (

Abstract

Context Probiotics are attracting wide attention today as a non-antibiotic feed additive in layer feed, and the number of studies in this field is on the increase. However, the results of the effects of probiotic-yeast supplementation on egg-production indices in laying hens are contradictory. Aim Therefore, the aim of the present study was to use meta-analytical methods to ascertain whether yeast-based diets improve feed intake (FI), feed conversion ratio (FCR), hen-day egg production (HDEP), egg mass (EM), egg weight (EW), Haugh unit (HU) and eggshell thickness (EST) in laying hens. Methods A search of four electronic databases for studies on the impact of yeast supplementation on egg-production indices published in English using a combination of search terms yielded 164 studies. Sixteen research publications with 20 771 laying hens met the criteria for inclusion in the meta-analysis. Data were pooled via random-effects model and are presented as standardised mean differences (SMD) with 95% confidence intervals (CI) for each effect size. Key results HDEP and EM showed a significant increase in the SMD of 11.3% (95% CI: 0.037–0.118, P = 0.003) and 22.5 g egg/hen.day (95% CI: 0.095–0.356, P < 0.001) respectively. Subgroup analysis showed that EST, EM, HDEP and FCR were improved in laying hens that received a yeast-based diet at <5 g/kg feed, compared with the group that received a yeast-based diet at >5 g/kg feed. The results indicated that trial country was a predictor of FI, FCR, EM, HDEP and EST in layers fed yeast-based rations. Conclusion These results suggest that feeding probiotic-yeast at <5 g/kg feed improved FCR, HDEP and EM in laying hens. Implications The results of the present meta-analysis will help poultry nutritionists develop the guidelines for standardising the experimental designs of future experiments on the use of probiotic yeast to enhance the productivity of laying hens.