In vitro rumen fermentation and digestibility of buffaloes as influenced by grape pomace powder and urea treated rice straw supplementation.

This study aimed to investigate the effect of grape pomace powder levels and roughage sources on gas kinetics, digestibility and fermentation of swamp buffaloes by using in vitro techniques. The experimental design was a 2 × 4 factorial arrangement in a completely randomized design. Factor A was two sources of roughage (untreated rice straw, RS, and 3% urea treated rice straw, UTRS) and factor B was four levels of grape pomace powder (GPP) supplementation (0, 2, 4, 6% of substrate) on a dry matter basis. Results revealed that GPP supplementation at 2, 4 and 6% of substrate influenced gas kinetics. Cumulative gas production tended to be lower in the supplemented group. In vitro true digestibility was higher in the GPP supplementation at 2% with UTRS while microbial mass was higher in the supplemented groups. Supplementation of GPP significantly increased the total volatile fatty acids, especially propionate. Calculated methane production was subsequently decreased in the supplemented groups. Bacterial population was higher while protozoal population was lower by GPP supplementation. It could be concluded that supplementation of GPP at 2% of the substrate with UTRS improved in vitro true digestibility, rumen fermentation end-products as well as reducing methane production.