Aspergillus spp. isolated from the bovine gastrointestinal tract improve organic acid profiles in Urochloa decumbens fermentation

Abstract

During the dry season, high productivity of cattle cannot be sustained through the supply of tropical forage alone, and microbial additives or probiotics represent potential alternatives to improve the performance of animals raised on pastures. In the present study, we evaluated organic acid profiles following the in vitro fermentation of Urochloa decumbens mediated by Aspergillus spp. isolated from the bovine digestive tract. Twenty fungal isolates were evaluated after 96 and 144 h of fermentation of U. decumbens hay (UDH) in saline solution, Sabouraud dextrose broth, or ruminal fluid. Following fermentation, organic acids in the culture media were detected using high-performance liquid chromatography. The production of major fermentation acids differed across fermentation times, fungal isolates, and culture media. Using UDH in saline solution as the sole substrate, gluconic acid was the major fermentation product of fungal isolates. Fermentation of UDH in Sabouraud dextrose broth produced butyric, citric, and propionic acids. Fermentation of UDH in ruminal fluid produced acetic, propionic, and butyric acids, with significant and positive correlations among their production. Five selected isolates increased propionate proportion relative to the control, indicating potential as additives or probiotics for ruminants receiving fiber-rich diets.