Improvement of the Nutritional Quality of Psophocarpus tetragonolobus Tubers by Fermentation with Ruminal Crabtree-Negative Yeasts on the In Vitro Digestibility and Fermentation in Rumen Fluid

Abstract

The purpose of this study was to determine how ruminal Crabtree-negative yeast affects the nutritional characteristics of winged bean (Psophocarpus tetragonolobus) tubers (WBT), in vitro gas and digestibility, and rumen fermentation. The experiment was carried out in a randomized complete design with a 5 × 2 (+1) factorial arrangement. Factor A determined the WBT products (a1 = dry WBT, a2 = fermented WBT without yeast in media solution, a3 = fermented WBT with Pichia kudriavzevii KKU20, a4 = fermented WBT with Candida tropicalis KKU20, and a5 = fermented WBT with Saccharomyces cerevisiae), whereas factor B determined the level of fermented WBT replacing cassava chips (b1 = WBT at 50% and b2 = 100% levels). The results of the experiment showed that the fermentation approach could increase the crude protein (CP) content of WBT by around 7% (p < 0.01). The WBT fermented with yeast lowered the number of aerobic bacteria during the fermentation process (p < 0.01). P. kudriazevii KKU20 yeast strain had a 17.3% higher final asymptotic gas volume (Vf) than the C. tropicalis KKU20. Crabtree-negative yeast had a higher in vitro dry matter digestibility (IVDMD) than Crabtree-positive yeast after 12 h of incubation (p < 0.01). Fermented WBT with yeast had a higher IVDMD after 24 h of incubation than fermented WBT without yeast in the media solution (p < 0.05). The fermented WBT with C. tropicalis KKU20 enhanced propionic acid (C3) concentrations when cassava chips were replaced for half of all of the diet (C3 ranged from 26.0 to 26.4 mol/100 mol; p < 0.01). Furthermore, Crabtree-negative yeast isolated from the rumen stimulates rumen bacteria more effectively than Crabtree-positive yeast (p < 0.01). According to our findings, nutritional enrichment with yeast might increase the in vitro gas production and digestibility of WBT. The study also demonstrated that Crabtree-negative yeast has a promising lead in terms of improving rumen fermentation quality. However, further research is required before deciding on an effective approach for optimizing the potential of WBT as a feed source.