PSII-16 Effect of dietary β-mannanase on growth performance, immune organ weight, and intestinal morphology of broiler chickens: A meta-analysis
Authors: Kim Hyun Woo , Lee Ji Hye , Lee Jae-Hwan , Kil Dong Yong 
Published: September 2024

Abstract
Beta-mannan (β-mannan) is commonly found in various feedstuffs and is well-recognized as an anti-nutritional factor for non-ruminant animals. In broiler chickens, dietary β-mannan is known to increase digesta viscosity, which is highly associated with decreased growth performance and intestinal health. Moreover, dietary β-mannan comprises surface components of various pathogens, which are recognized by innate immune systems, leading to an over-stimulation of immune system. This over-expression of immune system by dietary β-mannan is likely considered the reason for decreased performance and health in broiler chickens. One potential solution to mitigate this antinutritional effect of dietary β-mannan is the supplementation of exogenous β-mannanase in broiler diets. Previous studies have demonstrated that dietary supplementation of β-mannanase improves growth performance, immune responses, and intestinal morphology in broiler chickens by improving nutrient digestion and absorption in the gastrointestinal tract. However, existing research on the effect of dietary supplementation of β-mannanase has shown highly variable results, possibly due to large variations in experimental designs such as number of animals, animal genotype, experimental locations, and rearing conditions. Therefore, to obtain a comprehensive understanding of previously reported various results regarding the effect of dietary β-mannanase, it is necessary to integrate them into quantitative analysis through meta-analysis. Subsequently, the objective of this study was to conduct a meta-analysis summarizing the outcomes of the effect of dietary β-mannanase on growth performance, immune organ weight, and intestinal morphology of broiler chickens. A total of 27 eligible studies were identified through a comprehensive literature search conducted on Scopus, PubMed, Web of Science, and Google Scholar between January 2003 and December 2023. The meta-analysis was performed with the package “metafor” of the R software version 4.1.3. (R Core Team, 2023), and the standardized mean difference (SMD) and its 95% confidence interval (CI) were calculated using the random effect model. The results indicated that dietary supplementation of β-mannanase increased body weight gain (SMD = 2.09; 95% CI: 0.77 to 3.41; P = 0.003) and decreased feed conversion ratio (SMD = -2.98; 95% CI: -4.21 to -1.75; P &lt; 0.001) in broiler chickens (Table 1). Regarding intestinal morphology, dietary supplementation of β-mannanase increased jejunal villus height and crypt depth ratio (SMD = 2.07; 95% CI: 0.03 to 4.11; P = 0.048) and ileal villus height (SMD =2.06; 95% CI: 1.13 to 3.00; P = 0.002; Figure 1 and 2). Moreover, dietary supplementation of β-mannanase increased the relative spleen weight (SMD = 1.30; 95% CI: 0.25 to 2.36; P = 0.019) in broiler chickens. In conclusion, the current meta-analysis reveals that dietary supplementation of β-mannanase improves growth performance, intestinal morphology, and the relative spleen weight in broiler chickens.