Feed & Additive Magazine Issue 22 November 2022

ISSUE FOCUS 42 FEED & ADDITIVE MAGAZINE November 2022 Moreover, the potential effect of SCFA and MCFA without any protection would be limited because of prompt absorption and metabolism or both in the gastric area of the intestinal tract. New products have been developed through the formation of calcium and/ or sodium salt with the fatty acids or esterification of these acids prior to addition to feed. Esterification has an important advantage as the esterified SCFA and MCFA escape gastric digestion thus reaching the small intestine where they can exert their effect. When these acids, in salt or esterified form are fed to animals, positive effects on growth performance, intestinal microbial growth and health status of the animals are observed. Different mode of actions has been described to explain how short and medium fatty acids and their esterified forms can improve animal health and performance. These mechanisms involved the ability of these compounds to: • Maintain a healthy balance of bacteria in the gut Fatty acid esters contribute to a healthy gut balance by their antimicrobial properties, their ability to limit the invasion of intestinal epithelial cells by pathogens and to maintain microbiota with sufficient level of beneficial bacteria. Regarding their activities toward pathogens, the effect of fatty esters is both bactericidal (killing) and bacteriostatic (growth-inhibiting) depending on the length of the carbon chain, concentration, synergism among them, and target bacterium. The SCFAs and AGCM of C6-C10 act preferentially on Gram-negative bacteria such as E. coli, Salmonella and Campylobacter by limiting the adhesion and therefore the colonization of these bacteria on the intestinal cells. AGCMs with C12, such as lauric acids and derivatives, are particularly known for their effectiveness against Gram-positive staining bacteria, such as Clostridium perfringens, Staphylococcus spp. and Enterococcus spp. due to the easy-to-reach amphiphilic phospholipid double layer. Indeed, Gram negative bacteria have a more complex membrane structure that is more difficult to access. Membrane destabilization by the incorporation of fatty acid esters into the bacterial cell wall and cytoplasmic membrane, as well as the inhibition of bacterial lipases, which are necessary for the colonization of the skin and the intestinal mucosa, may be the main mode of action. Lipid-encapsulated viruses and some parasites can also be targets for fatty acids esters; involving also activities of fatty acids esters on membrane degradation, disrupting the functioning of microorganisms and compromising their infectivity. • Promote the gut maturation and integrity Challenges due to environment, nutritional stresses or related to health status of animal, can cause changes in intestinal morphology. Initially, a large size of villi is a sign of good digestive health. The absorption surface being important, the food will be well valued. Conversely, a great depth of the crypts is a sign of maldigestion. These crypts are the site of cell renewal. Thus, the shallower the crypts, the faster the renewal and the faster the nutrients are. SCFAs and MCFAs can be directly absorbed and supply energy to promote the renewal and repair of intestinal epithelial cells, maintain the integrity of intestinal mucosal barrier function. • Modulate the immune system and prevent inflammation The gastrointestinal tract is not only an important organ for the digestion, absorption, and metab-

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