Use of Microorganisms as Nutritional and Functional Feedstuffs for Nursery Pigs and Broilers

SIMPLE SUMMARY: The use of microorganisms has become a trend as nutritional and functional feedstuffs become widely used in swine and poultry diets. Microorganisms, as coproducts obtained from the food industry and biorefineries, can reduce not only the burdens of the natural ecosystem but also the high costs of feedstuffs. It is possible to mitigate food and land competition with humans in the current global issues. These microorganisms could be promising and sustainable alternatives in animal diets because they contain highly valuable proteins, amino acids, fatty acid composition, and biogenic metabolites, which are beneficial for animal production. Microorganisms could be good alternatives to replace plant and animal-based protein supplements with high protein and a balanced amino acid composition. Lipid-rich microalgae and yeasts could be alternative energy feeds with valuable fatty acids used to enhance intestinal health and meat quality. In addition, microorganisms could be functional feed additives due to their cell contents and their cell wall bioactive components. However, there still are some limitations to using microorganisms, including the sources and dose of those microorganisms, which may cause negative effects on growth and health. Thus, this research focused on investigating the use of nutritional and functional microorganisms as feedstuffs and feed additives to replace conventional feedstuffs for enhancing the growth and intestinal health of nursery pigs and broilers. ABSTRACT: The objectives of this review paper are to introduce the structures and composition of various microorganisms, to show some applications of single cells as alternative protein supplements or energy feeds in swine and poultry diets, and to discuss the functional effects of microorganisms as feed additives on the growth performance and intestinal health of nursery pigs and broilers. Microorganisms, including bacteria, yeasts, and microalgae, have been commonly supplemented in animal diets because they are cost-effective, stable, and have quantitative production that provides nutritional and functional benefits to pigs and broilers. Microorganisms could be alternative antibiotics to enhance intestinal health due to bioactive components from cell wall components, which interact with receptors on epithelial and immune cells. In addition, bioactive components could be digested by intestinal microbiota to produce short-chain fatty acids and enhance energy utilization. Otherwise, microorganisms such as single-cell protein (SCP) and single-cell oils (SCOs) are sustainable and economic choices to replace conventional protein supplements and energy feeds. Supplementing microorganisms as feedstuffs and feed additives improved the average daily gain by 1.83%, the daily feed intake by 0.24%, and the feed efficiency by 1.46% in pigs and broilers. Based on the properties of each microorganism, traditional protein supplements, energy feeds, and functional feed additives could be replaced by microorganisms, which have shown benefits to animal’s growth and health. Therefore, specific microorganisms could be promising alternatives as nutritional and functional feedstuffs in animal diets.