As described in Part I, animal gut health is a symbiotic relationship, among feed quality, gut function and microbiota, includingfeed digestion, mucosal and barrier function, immune response and redox balance as proposed by van de Gutchte et al. (2018) for healthy, pre-disease and disease states (Figure 1).

Figure 1 Alternative stable states and critical transition in the gut microbiota-host symbiosis

Many factors can contribute to the symbiotic relationship. In Part I, we described the impact of feed microbial and oxidative deterioration on gut health, and how Adisseo's portfolio of products and services can contribute to feed hygiene quality that subsequently benefits gut health by inhibiting mold growth during storage, eliminating pathogens such as Salmonella in feed and water, preventing oxidative deterioration of fat-rich raw materials and feeds, alleviating mycotoxin contamination risks, especially those harmful to gut functions – T-2 toxin and deoxynivalenol, throughout the feed production cycle.

Although clean and safe feed presents a good start towards gut health, the digestibility of feed is another important pillar not to be neglected. In this article, we will explain Step 2 of Adisseo's holistic 3-step approach for gut health management, aiming at improving overall feed digestibility, reducing indigestible fractions, and delivering certain probiotic and prebiotic effects to the gut.

Feed digestibility: Indigestible fraction acting on the microbiota

Although animals have a high capacity to digest and absorb the nutrients from feed, the level of digestion is affected not only by the availability of nutrients, but also by the type and level of antinutritional factors (ANF) such as phytate, arabinoxylans and other non-starch polysaccharides (NSP). Based on these factors, we can evaluate the digestibility level in each diet and the amounts of nutrients left feeding the microbiota in the gut.

The indigestible fractions will directly influence the development of microbiota, which could be either in a positive manner – a microbiota producing short chain fatty acids, conserving the mucin layer and the intestinal wall integrity, or in a negative manner when there is an excess of indigestible nutrients and specific fractions in the intestinal tract, the microbiota tends to grow unbalanced, creating conditions towards a pre-disease status.

In an antibiotic-free animal production, it is highly recommended to decrease the indigestible amino acids, fats, carbohydrates and other components, which is difficult to achieve in a practical feed formula. However, there are some good practices that can help the animals to better develop its microbiota and increase their digestion capacity.

Good Practice No. 1: Precise Nutrition Evaluation on feed raw materials.

Precise evaluation could allow the nutritionists to produce well-balanced feeds, contributing to improved digestion by reducing the indigestible fractions. Adisseo Precise Nutrition Evaluation (PNE) service is one of the best tools in kind, thanks to its in vivo Near Infrared Reflectance (NIR) models, helping nutritionists to precisely predict both digestible and indigestible proportions of each amino acid in feed ingredients. PNE also offers prediction of phytate phosphorus level and soon will include updated values for NSP concentrations. All such data of feed ingredients can help estimate the regular level of digestible nutrients as well as the indigestible fractions, potentially for the microbiota.

Good Practice No. 2: Use exo-enzymes, such as phytase and multi-carbohydrase.

These enzymes will work on various substrates, improve the digestibility and absorption of phosphorus, and lift the overall energy level of the diet. Research showed that using a high dose of phytase could increase the phosphorus retention from close 35% to 55%, and reduce the phytate's chelation with amino acids, leading to higher absorption of amino acids.

Regarding the carbohydrase, the mechanism is much more complex. For example, Rovabio is a multi-carbohydrase complex, containing five different xylanases, beta-glucanases, cellulases, arabinofuranosidases and feroloil-stearase. All these enzymes coming from one single fermentation of Talaromyces versatilis that ensure compatibility and synergistic effects. Studies by many research institutions and commercial farms have proven that Rovabio can significantly enhance metabolizable energy, digestibility of amino acids and fats in diets. Such effects come from the capacity of Rovabio to break-down the NSP complex, to decrease viscosity, and to certain extent, decrease the cage effect caused by the vegetal cell walls, release the entrapped nutrients to digestive enzymes (such as proteases, amylases and lipases), hence improve the overall digestibility. A prediction tool has also been developed based on a meta-analysis of internal data, to better predict the digestive effect of this multi-enzyme complex.

Moreover, it is worth mentioning that the effects of enzymes can go beyond digestibility and energy contribution, since the enzymatic reactions will produce an impact on gut microflora, offering environment or opportunity for microbial function – probiotic or prebiotic, or both, in the gut.

Good Practice No. 3: Evaluate and choose enzymes that deliver beneficial effects to gut health.

Recently, scientists (Bonin et al., INRA, Nantes) have observed that Rovabio could improve the quality of digestion due to the outcome of its enzymatic action: decrease arabinoxylan molecular size. These smaller arabinoxylan fractions can work as a prebiotic, in sufficient amounts to send a signal and improve the microbiota function in a positive manner. Trials conducted in France on broiler, and in Brazil and Spain on swine, demonstrated that such actions significantly improve and stabilize the microbiota in the gut. One of these studies was published in ISIGH (2017), Yacoubi et al. demonstrated, at day 14 of a 2-week period of broiler trial, that the arabinoxylan fraction produced by Rovabio significantly changed the microbiota composition in the cecum favoring beneficial bacteria (Figure 2), decreased the marker of intestinal inflammation – T-Cell infiltration in ileum and cecum (Figure 3), and increased the short chain fatty acid produced in the cecum, mainly the acetic and butyric acids in the digesta (Figure 4). At the same time, performance parameters such as feed intake, body weight gain and FCR were also significantly improved by supplementation of the arabinoxylan fractions produced by Rovabio in the feed at 0.1% level (Figure 5). In addition, after applying Rovabio in swine diets, similar beneficial effects to swine gut health were also observed by Willamil et al. (2012) and Torres et al. (2020).

Figure 2 Rovabio fraction significantly increased bacteria of the Enterococcaceae and Clostridiaceae 1 families in the ileum and Lachnospiraceae and Ruminococcaceae family in the cecum of broilers at day 14 (P<0.05)

Figure 3 Rovabio significantly decreased the T-cells infiltration in the ileum and cecum of broilers at day 14 (P<0.05)

Figure 4 Rovabio improved the short chain fatty acids, mainly the acetic and butyric acids in the digesta of broilers at day 14

Figure 5 Rovabio significantly improved feed intake, body weight gain and feed conversion ratio for broilers at day 14

Conclusion

Precise evaluation on feed raw materials based on NIRS enables a better procurement of feed ingredients, and precise formulation that leads to minimum indigestible fractions for microbiota proliferation in the gut. Applying efficient phytase together with multi-carbohydrates-degrading enzymes further improves the overall digestibility of major nutrients such as energy, amino acids and phosphorus, benefiting microbial or even produce a prebiotic effect, to induce a healthy microbial environment in the gut.

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Article made possible through the contribution of Dr. Marcio Ceccantini, Adisseo France S.A.S.; Dr. Kevin Liu and Dr. Claire Xu, Adisseo Singapore

Adisseo's holistic 3-Step approach to improve gut health in animals: Part II