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Xylanase enhances the intestinal barrier function of soy-fed tilapia

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By Milthon Lujan

Nile tilapia. Source: Earlham Institute
Nile tilapia. Source: Earlham Institute

Soybean meal (Glycine max) is one of the most important protein sources for fish feed, but the non-starch polysaccharides in soybean meal can impair the intestinal barrier function.

The addition of exogenous enzymes is an effective method to alleviate the adverse effects of non-starch polysaccharides on host health.

To investigate whether xylanase alleviates the negative effects induced by soybean meal on the intestinal barrier and how it does so, researchers from East China Normal University and the Institute of Animal Sciences fed Nile tilapia a diet of soybean meal supplemented with or without xylanase, and examined intestinal morphology, transcriptome analysis, and intestinal microbiota composition.

Effects of non-starch polysaccharides

Non-starch polysaccharides in soybean meal act as an antinutritional factor that causes dysfunction of the fish intestinal barrier. Additionally, non-starch polysaccharides can increase feed viscosity and delay intestinal transit time, which in turn influences nutrient availability and microbial composition in the intestine.

Moreover, scientific literature reports that non-starch polysaccharides in the diet reduce the height of small intestinal villi and inhibit the growth of beneficial bacteria.

In aquaculture, soybean meal or 5 g/kg of non-starch polysaccharides in the diet reduced nutrient availability, impaired distal intestinal integrity, and decreased intestinal villus length.

Therefore, eliminating the adverse effects of non-starch polysaccharides on host health is essential for the application of plant proteins in aquaculture feed preparation.

The importance of xylanase

Xylanase is one of the enzymes responsible for degrading non-starch polysaccharides and can specifically hydrolyze xylan. However, xylanase is scarce and absent in the fish intestine.

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Various studies have reported that the addition of xylanase to the diet of aquatic animals decreases digesta viscosity, improves growth performance, increases nutrient digestibility, and enhances protein efficiency ratio.

Additionally, xylanase has been found to modulate the composition of the intestinal microbiota. The intestinal microbiota can ferment the oligomers released by xylanase to produce metabolites such as short-chain fatty acids (SCFAs), which have beneficial effects on host health.

In this study, researchers fed Nile tilapia with two diets that included soybean meal and soybean meal + 3000 U/kg of xylanase for 8 weeks.

Effects of xylanase

“In the present study, we found that the addition of 1500 U/kg of xylanase to soybean meal did not affect final weight, whereas the administration of 3000 U/kg of xylanase in the soybean meal diet decreased the weight gain of Nile tilapia,” they reported.

They explained that the decrease in weight gain was mainly due to decreased visceral-somatic index, but carcass weight increased in the xylanase treatment, suggesting that xylanase increased the proportion of edible parts in Nile tilapia.

Furthermore, the researchers reported that “dietary xylanase improved intestinal morphology and decreased serum lipopolysaccharide (LPS) concentration.”

They also highlighted that the microbiome analysis showed that the addition of xylanase in soybean meal altered the composition of the intestinal microbiota and increased butyric acid concentration in the intestine.

Conclusion

The scientists concluded that “Overall, xylanase supplementation in soybean meal altered the composition of the intestinal microbiota and increased butyric acid content, which can repress the PERK/ATF4 signaling pathway and enhance muc2 expression to improve the intestinal barrier function of Nile tilapia.”

They also emphasized that the study’s results reveal the mechanism by which xylanase improves the intestinal barrier and provide a theoretical basis for the application of xylanase in aquaculture.

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Contact
Meiling Zhang
Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences
East China Normal University
Shanghai, 200241, China
Email: mlzhang@bio.ecnu.cn

Reference (open access)
Wang, T., Zhou, N., He, J. et al. Xylanase improves the intestinal barrier function of Nile tilapia (Oreochromis niloticus) fed with soybean (Glycine max) meal. J Animal Sci Biotechnol 14, 86 (2023). https://doi.org/10.1186/s40104-023-00883-8

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