We studied the effects of yak rumen anaerobic fungus Orpinomyces sp. YF3 on the fermentation of stalks in 2 experiments. The first experiment investigated whether Orpinomyces sp. YF3 (0, 5, 10, 15%) could promote the in vitro fermentation of wheat straw. We found that 15% addition of Orpinomyces sp. YF3 increased the activity of xylanase and acetylesterase and reduced the NH3 -N concentration with 3-d fermentation. In addition, the 15% addition improved the percentage of acetate and the ratio of acetate to propionate (A:P) and decreased the percentage of butyrate with 5-d fermentation. The second experiment explored the effects of repelling rumen fungi and 15% addition Orpinomyces sp. YF3 on fermentation profile and microbial diversity. Four treatments were set up: control (C), antibiotic (CA, d 0 treated with 0.25 mg/mL cycloheximide), yak fungi (CF, d 4 to 8 replaced saliva with 15% Orpinomyces sp. YF3 culture), and antibiotic + yak fungi (CAF + Orpinomyces sp. YF3) groups. CF improved the activity of carboxymethyl cellulase and avicelase, the concentration of NH3-N, total volatile fatty acid (VFA) and acetate, and A:P, but reduced propionate concentration. Additionally, CF increased the relative abundance of fiberdegrading-related bacteria (Rikenellaceae_RC9_gut_group, Ruminococcus, Pyramidobacter, etc.) and acetogenic-related bacteria (Anaerovorax), but decreased that of starch-degrading bacteria (Prevotella), propionate-producing-related bacteria (Fibrobacter), and 4 yeasts (Vishniacozyma, etc.). Similarly, CAF improved the activity of avicelase, increased acetate percentage, and reduced propionate percentage and total VFA concentration. CAF showed similar effects on microbial diversity, with increased relative abundance of fiber-degrading-related bacteria (Christensenellaceae_R-7_group) and acetogenic-related bacteria (Anaerovorax), and decreased relative abundance of starch-degrading bacteria (Streptococcus). In conclusion, treating forage with Orpinomyces sp. YF3 is probably a practical strategy to promote roughage degradation in ruminants.
Key Words: yak, rumen anaerobic fungi, stalk degradation, microorganism.
Presented at the 9th Symposium on Gut Health in Production of Food Animals, St. Louis, USA, 2021. For information on the next edition, click here.