Meta-Analysis of Bacillus in Laying Hen Nutrition: Feed Intake, Feed Conversion Ratio and Egg Productive Indices

This data synthesis study aimed to explore the impact of bacillus additive on performance of laying hens. Three bibliographic databases were scanned, with no restrictions on language and date. The inclusion criteria were randomised and controlled trials using non-diseased laying hens and published in peer-reviewed journals. The eligibility criteria were also information on measured performance parameters and studied moderators. Eighteen (18) studies passed the eligibility conditions for the study and were analysed in Open MEE software. Results were displayed as Standardised Mean Difference (SMD) at 95% confidence intervals (CI). Results showed that bacillus supplementation improved feed conversion ratio (SMD = -0.21;95% confidence intervals (CI) = -0.29, -0.12) and increased hen-day egg production (SMD = 0.21; 95% CI = 0.16, 0.27)]. Feed intake was not affected by dietary bacillus supplementation. In contrast, bacillus supplementation increased egg weight (SMD = 0.08; 95% CI = 0.03, 0.12) and egg mass (SMD = 0.27; 95% CI = 0.16, 0.38) compared with the control. Restricted subgroup and mixed effect meta-regression analyses showed that pooled results were changed by the studied moderators. In conclusion, results suggested that bacillus supplementation could be added to laying hen diets to improve performance indices.