Exogenous Enzymes as Zootechnical Additives in Monogastric Animal Feed: A Review

Feed enzymes have been extensively used in livestock diets to enhance nutrient digestion and promote their growth performance. Indeed, recent research has indicated that feed enzymes, notably phytase, protease, and xylanase, function as catalysts, facilitating the breakdown of phytic acid, proteins, and β-1,4-xylan bonds and offering prospective advantages linked to the intestinal well-being and microbiota of young pigs and chickens. Various feed enzymes are currently being added to the diets of swine and broiler chickens. The potential enzymes used in the feed industry include cellulase, β-mannanase, β-glucanases, xylanases, phytases, proteases, lipases, and galactosidases. Though significant research has been conducted on phytase, protease, and xylanase, consistent findings, particularly in terms of improving nutrient digestibility and promoting growth performance of monogastric animals, are still limited. Also, the outcome of recent studies raises the question whether phytase and xylanase could play functional roles beyond increasing nutrient digestibility and intestinal health, such as positively modulating the intestinal microbiota and reducing environmental problems. Therefore, in this review we aimed to address the functional roles of exogenous enzyme activities in monogastric animal diets. Also, we sought to explore the advantages of these enzymes in enhancing the nutritional value of both alternative and conventional feedstuffs.