ß-mannanase feed supplementation improves broilers performance and restores dysbiosis in broilers fed a guar gum supplemented diet

The Problem

β-mannanases are enzymes that can hydrolyze β-mannans, an anti-nutritional fibre present in many feed ingredients, of which guar gum is the classical example. We evaluated the effects of β-mannanase supplementation on the performance, intestinal morphometry and gut microbiome of broilers fed with a diet rich in β-mannans.

How we investigated or researched the problem

One-day old Ross broiler chickens (n= 756) were randomly divided into three treatments (12 pens with 21 animals each): control (C), guar gum (GG) (inclusion level 17.90 g/kg starter and 16.50 g/kg grower) and guar gum+β-mannanase (GG+E) (Hemicell^® 330g/ton). On days (d) 1, 14, 21, 28 and 35, average body weight (ABW), daily weight gain (DWG), daily feed intake (DFI), and feed conversion rate (FCR) were measured. On 14 and 28 d, one animal per pen was euthanized. Duodenum and ileum were fixed in formalin, and villi height, crypt depths and the villi:crypt ratio was calculated. Also, ileal and caecal content were obtained for microbiome analyses using 16S rDNA sequencing.

Results

The guar gum ingestion significantly affected animal performance decreasing the ABW, DWG and increasing the FCR at 14, 21, 28 and 35d. Mannanase supplementation resulted in improvements of these performance parameters, to control group levels. The GG group also showed a reduced DFI compared to the GG+E group among 0-35 days. GG supplementation resulted in an increase in the ileal villi height and villi crypt:ratio, whereas the GG+E group showed identical ileal villi:crypt ratios as compared to control animals. No differences were observed in the duodenum.

GG ingestion induced changes in the ileal and caecal microbiota composition. At genus level GG increased Escherichia-Shigella (ileum 14d; caecum 14 and 28d) and Lactobacillus (caecum at both ages), and decreased the abundance of the beneficial microbiota Candidatus Arthromitus (ileum 14d), Faecalibacterium (ileum and caecum 28d), and Butyricicoccus (ileum and caecum 28d).

Implications / Conclusions

β-mannans present in feed ingredients has been associated with negative effects on nutrient digestibility. We show that guar gum impairs broiler performance, while β-mannanase inclusion in the diet restored performance to control conditions. The increase in the ileal villi height in the GG treatment can be a compensatory mechanism due to the lower diet digestibility in the proximal part of the intestinal tract. GG decreased the abundance of butyrate producing genera, and increased the Escherichia-Shigella and Lactobacillus abundance.

Butyrate it is the preferred energy source for the enterocytes. Carbohydrate malabsorption in the upper intestine is hypothesized to have caused an overgrowth of lactic acid-producing bacteria (Lactobacillus), resulting on accumulation of lactic acid. Addition of enzymes such as β-mannanase can maximize the use of the nutrients and improve performance in mannan-rich diets, and also restore a dysbiosis to normal levels.

Presented at the 7th International Conference on Poultry Intestinal Health, Cartagena, Colombia, 2022. For information on the next edition, click here.