The aim of this experiment was to test the effect of yeast-fermented de-hulled rice (YDR) levels of protein-rich feed with different kinds of roughages on in vitro gas production, nutrient degradability, and rumen fermentation. The treatments were randomly assigned according to a 2 × 4 factorial arrangement in a completely randomized design (CRD). The two experimental factors were comprised of two roughages (R) (untreated rice straw (RS) and sweet grass hay (SGH)) and four ratios of roughage to yeast-fermented de-hulled rice (R:YDR) (100:0, 75:25, 50:50, and 25:75). Thus, there were 8 treatment combinations. The results revealed that the interaction between R and R:YDR ratios influenced on the gas production rate constant for the insoluble fraction ratio (c) (P < 0.01). The in vitro dry mater degradability (IVDMD) was improved by SGH and R:YDR ratios (P < 0.05). Supplementation of YDR with both of roughage sources (RS and SGH) increased propionate (C3) (P < 0.05) and total VFA production (P < 0.01); both factors showed interactive effects on rumen methane production (P < 0.01). Moreover, bacterial population was significantly increased by the SGH:YDR ratios (P < 0.05). Therefore, it could be summarized that supplementing YDR, an enriched protein source with SGH:YDR ratio at 50-75:50-25 ratio significantly enhanced nutrient degradability and in vitro rumen fermentation efficiency.
Keywords: De-hulled rice; Fermentation; In vitro gas production; Yeast-fermented product.