Guar gum as galactomannan source induces dysbiosis and reduces performance in broiler chickens and dietary b-mannanase restores the gut homeostasis

Galactomannans are abundant nonstarch polysaccharides in broiler feed ingredients. In broilers, diets with high levels of galactomannans have been associ-ated with innate immune response stimulation, poor zoo-technical performance, nutrient and lipid absorption, and excessive digesta viscosity. However, data about its effects on the gut microbiome are scarce.-Mannanases are enzymes that can hydrolyze-mannans, resulting in bet -ter nutrient utilization. In the current study, we have eval-uated the effect of guar gum, a source of galactomannans, supplemented to broiler diets, either with or without-mannanase supplementation, on the microbiota compo-sition, in an attempt to describe the potential role of the intestinal microbiota in-mannanase-induced gut health and performance improvements. One-day-old broiler chickens (n = 756) were randomly divided into 3 treat-ments: control diet, guar gum-supplemented diet (1.7%), or guar gum-supplemented diet +-mannanase (Hemicell 330 g/ton). The zootechnical performance, gut morphom-etry, ileal and cecal microbiome, and short-chain fatty acid concentrations were evaluated at different time points. The guar gum supplementation decreased the zoo-technical performance, and the-mannanase supplemen-tation restored performance to control levels. The mannan-rich diet-induced dysbiosis, with marked effects on the cecal microbiota composition. The guar gum-sup-plemented diet increased the cecal abundance of the gen-era Lactobacillus, Roseburia, Clostridium sensu stricto 1, and Escherichia-Shigella, and decreased Intestinimonas, Alistipes, Butyricicoccus, and Faecalibacterium. In gen-eral, dietary-mannanase supplementation restored the main microbial shifts induced by guar gum to levels of the control group. In addition, the-mannanase supplemen-tation reduced cecal isobutyric, isovaleric, valeric acid, and branched-chain fatty acid concentrations as com-pared to the guar gum-supplemented diet group, suggest-ing improved protein digestion and reduced cecal protein fermentation. In conclusion, a galactomannan-rich diet impairs zootechnical performance in broilers and results in a diet-induced dysbiosis.-Mannanase supplementation restored the gut microbiota composition and zootechnical performance to control levels.

Automated summary

Galactomannans in broiler feed can negatively impact zootechnical performance and gut microbiota composition. Mannanase supplementation can restore the gut microbiota and improve performance to normal levels.