The Indian Journal of Small Ruminants

Among different type of concentrate feedstuffs (CFS) 9 grains, 4 cakes and 3 by-products were taken to characterize in vitro gas and methane production. These ingredients were grouped in to 2 broad categories such as narrow (1:1 or 2:1) and wider (7:1) ratio of carbohydrate (CHO) to crude protein (CP). Ether extract (EE) was taken as covariate. Cumulative gas production (CGP) was significantly rapid till 12 h of incubation in narrow CHO: CP ratio CFS. CGP in wider CHO: CP ratio CFS was 65 (P< 0.001), 37 (P< 0.001) and 21 (P< 0.001) % lesser than other category at 4, 8, 12 h of incubation however, difference was reduced to 6 and 3% at 18 and 24 h of incubation. Difference in CGP at initial hours of incubation was greater for cereals and pulses rather than by-products. First order gas production kinetics indicated significantly difference in rate constant of fermentation and t-half time between CFS having narrow and broader ratio of CHO: CP. Lag time and total gas production had significant correlation (P< 0.001) with methane proportion with adjusted R² value of 0.61 (P< 0.001). CP and EE were negatively correlated with methane proportion in total gas but, only r-value of the latter was significant (P< 0.05). TC was positively related yet its r-value was not significant. CHO however, was positively (r = 0.79; P< 0.001) and, CP (r = −0.47, P< 0.05) or EE (r = −0.63, P< 0.01) were negatively related with total gas production. Study concluded that the gas production pattern of CFS indicated that the narrow CHO: CP ratio was important for initial rapid fermentation. Although extent of fermentation was similar with CFS with wider CHO: CP ratio, their initial fermentation was. Rate constant and t-half of gas production was dependent of characteristics of feedstuffs. Fat content had significant negative affect on methane production. This information can be useful in formulating environ-friendly concentrate supplements using CFS having narrow CHO: CP ratio to balance roughage diets having high rumen retention time.