EVALUATION OF ASPERGILLUS ORYZAE POSTBIOTIC ON NUTRIENT DIGESTIBILITY, GUT MICROBIOME, AND METABOLOME IN GROWING PIGS FED HIGH FIBER DIETS

Abstract

Substantial amounts of low-cost, high fiber coproducts produced from various agro-industrial processes are incorporated into swine feed with the aim of reducing the cost and the environmental impacts of food animal production. Because dietary fiber (DF) is not well utilized by pigs, effective strategies are needed to improve the energy and nutrient utilization efficiency of using high fiber coproducts in swine diets. The objective of this thesis was to determine the potential of Aspergillus oryzae postbiotic (AOP) for improving nutrient digestibility of high fiber coproducts in growing pig diets and the underlying mechanisms. Results from the first and second experiments showed that the addition of 0.05% AOP to corn distillers dried grains with solubles, rice bran, or wheat middlings and diets containing these high fiber ingredients increased energy and nutrient digestibility in vivo and in vitro. The magnitude of the AOP response is ingredient- and diet-dependent, which suggested that the effectiveness of fiber-degrading feed additives is associated with DF type and composition of ingredients. Results from the third experiment suggested that dietary addition of AOP significantly altered the diversity and composition of the microbial community and metabolome in the ileal digesta and feces of growing pigs. Dietary addition of AOP alters the abundance of several bacteria that were significantly correlated with nutrient digestibility, including key players of the fiber-degrading bacteria. Overall, findings from this thesis provided the first evidence that AOP is effective in increasing the energy and nutritional value of swine diets containing different types of high fiber ingredients and new insights into mechanisms of action of AOP in pigs.