SPECIAL STORY 72 FEED & ADDITIVE MAGAZINE November 2023 THE DIGESTIVE TRACT: FACILITATING NUTRIENT UPTAKE AND IMMUNE FUNCTION Expertly formulated prebiotics in aquafeed can optimize immune defense, resulting in significant alterations within the digestive tract. They particularly affect the structure of the gut and the composition of the microbiome. After ingestion, macronutrients such as proteins, fats and carbohydrates undergo a series of digestive processes that break them down in preparation for absorption and assimilation by the fish. These smaller components enter the body through the gut wall, which is lined with microvilli, structures that increase the gut’s surface area, promoting increased nutrient absorption. A compromised digestive tract can lead to poor performance, characterized by a higher feed conversion ratio (FCR) and reduced immune response against pathogens. Facilitating a diverse microflora population is essential for enhancing intestinal development, ensuring gut integrity and optimizing the digestion process. Within the gut, mucus-producing cells promote a thick and protective mucus layer, protecting the delicate tissue underneath. MODE OF ACTION OF MOS FOR DIFFERENT FISH SPECIES Now that we have a thorough understanding of the immune system and digestive tract, let’s delve deeper into examining the specific impacts of the prebiotic mannan oligosaccharide (MOS). MOS is derived from the yeast Saccharomyces cerevisiae, commonly known as “baker’s yeast.” Through a sophisticated refinery process, MOS is extracted from the yeast and incorporated into the feed ingredient mixture. The effectiveness of MOS is determined by several factors, including fermentation conditions, genetic strains and various processing parameters. As a result, not all forms of MOS yield identical effects. At Alltech Coppens, we combine Bio-Mos® and Actigen® with a chelated mineral mix, Bioplex®, to create Aquate®, which is integrated into our feed formulations. At Alltech, research is the primary focus. To determine the effects of Bio-Mos on fish performance and gut health, several R&D actions were undertaken. For rainbow trout, it was observed that beneficial bacteria colonization was promoted in the gut of a healthy individual when gut bacterial load was reduced (Dimitroglou et al. 2007). Furthermore, Bio-Mos has demonstrated improvements in microvilli density and length, contributing significantly to improved nutrient absorption and enhancing fish performance (Sweetman et al. 2008). Finally, Bio-Mos can enhance the thickness of the mucus layer across the skin, gills and gut, creating a prophylactic effect for many fish species (Sweetman et al., 2010). The effects of MOS on fish health and growth have been extensively documented across numerous peer-reviewed papers. In rainbow trout, the inclusion of MOS positively influenced growth rates and improved FCR and survival rates. It also displayed positive effects on growth in a wide variety of other species, such as brook trout, sturgeon, common carp, koi, African catfish, European sea bass and sea bream. Additionally, beneficial effects were observed in gut structure, pathogen-binding capacity (both in vitro and in vivo), immunostimulant propImage 2. Results after Aquate technologies were adopted in the Mediterranean Sea bass industry on large-scale commercial farms
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