In vitro ruminal fermentation, protein and carbohydrate fractionation, methane production and prediction of twelve commonly used Indian green forages.

Methane production and energy loss of 12 green forages were investigated in vitro in a completely randomized design using inoculum from buffaloes. The forages, which included Hordeum vulgare, Avena sativa, Trifolium alaxendrinum, Medicago sativa cv. Anand-2, Medicago sativa cv. T-9, Pennisetum purpureum, Panicum maximum, Saccharum officinarum (SOT), Arachis hypogea (AHL), Grewia optiva leaves (GOL), Leucaena leucocephala leaves and Sorghum bicolor were also partitioned into crude protein (CP) and carbohydrate (CHO) fractions using the Cornell Net Carbohydrate and Protein System. In vitro gas production and dry matter (DM) digestibility were estimated using rumen fluid from 2 fistulated buffaloes. Correlation analysis was used to establish relationships between measured variables and CH4 production. Crude protein contents of the forages were lowest (P<0.001) in the grasses/cereals and highest (P<0.001) in the legumes. Accumulation of neutral detergent fiber, acid detergent fiber (ADF) and cellulose was higher in the grasses and cereals, whereas the reverse occurred with legumes. The proportion of degradable CP fractions ranged from 0.70 to 0.83 of total CP, with higher (P<0.001) CP fractions for legumes vs. grasses/cereals. Overall, legumes had a higher unavailable CHO fraction than the grasses or cereals. Legumes were more fully degraded in vitro than in grasses and cereals, being highest (P<0.001) in GOL and least in SOT. After 24 h of incubation, CH4 production (g/kg DM) was higher (P<0.001) in legumes than grasses or cereals. Loss of energy as CH4 was higher (P<0.001) in AHL and GOL than in the other forages, although there were no differences among the groups; cereals, grasses and legumes. Only ADF and cellulose were positively correlated (P<0.05) with CH4 production (g/kg DM). Because of the substantial amount of dietary gross energy lost in CH4, knowledge of the CH4 potential of these forages will help in formulating low CH4 producing diets for ruminants.