Effect of multicarbohydrase enzymes containing α-galactosidase on the growth and apparent metabolizable energy digestibility of broiler chickens: a meta-analysis

•Enzymes including α-galactosidase improved the weight and feed efficiency of broilers.•Multienzyme complexes, containing a-galactosidase increased nutrient digestibility.•Meta-analysis is a useful tool to summarize findings from controlled studies. Exogenous enzyme supplementation is a valid strategy to improve nutrient availability and growth performance in broilers. Traditional carbohydrases, such as xylanase and β-glucanase, are well-researched solutions to increase the nutritional value of cereal grains, whilst reducing any negative impact of associated viscous polysaccharides. The feeding value of soybean meal and other protein rich oilcakes may not be fully exploited with traditional enzymes, as structures such as galacto-oligosaccharides and pectins require specific α-galactosidase, mannanase and other hemicellulolytic enzymes. This study aimed to summarize, in a meta-analysis, the results from independently run randomized controlled studies in various global locations that evaluated the effect of two distinct multicarbohydrase formulations, in which an α-galactosidase was combined with either xylanase (AGX) or β-glucanase (AGB). Through meta-regression analysis, the mean difference effects of AGX and AGB supplementation on broiler final body weight (BW), feed conversion ratio (FCR) and nitrogen-corrected apparent metabolizable energy (AMEN) were calculated for each relevant study. Fixed and random-effects models were used to compute the standardized mean difference (SMD) and confidence intervals, with corrective actions taken to ensure compliance with publication bias and heterogeneity by the Egger test and the Cochran Q test. Adjusted models showed that the AGX supplementation increased broiler BW (SMD=+30 g; 95 % CI: 0.08_0.48; P = 0.006) and improved FCR (SMD=−0.01 g/g; 95 % CI: -0.51_-0.11; P = 0.002). A composite evaluation of independent studies showed increased AMEN in broilers supplemented with AGX (SMD=+58 kcal/kg; 95 % CI: 0.45_1.10; P