Microbial profiles, in vitro gas production and dry matter digestibility based on various ratios of roughage to concentrate

The study assessed the effects of different roughage to concentrate ratios on enteric methane production, rumen fermentation and microbial counts. These ratios were 80:20, 50:50, and 20:80 for diets 1, 2, and 3, respectively. No significant differences were observed in total gas production among diets; however, methane emissions increased (P < 0.05) with increased roughage in diet. The pH was greater (P < 0.05) in diet 1 compared to diets 2 and 3 (6.38 vs 6.17 and 6.07). In vitro dry matter digestibility increased with decreased roughage ratios (47.67, 61.67, 67.33 % for diets 1, 2 and 3, respectively). Similarly, total volatile fatty acids (mM/100 mL) also increased with decreased roughage ratios [diet 1 (5.38); diet 2 (6.30); diet 3 (7.37)]. Methanogen counts, total bacterial counts and protozoal counts were lower (P < 0.05) in diet 3 compared to diet 1 and 2. However, total fungal counts were higher in diet 1 compared to diet 2 and 3. The results indicate that methane emission, enteric fermentation patterns, and change in methanogens population appear only with higher level of roughage. These findings are important for reducing methane without any impact on rumen performance.