Influence of inoculum source on gas production profiles

Gas production equipment is used in many locations to study rate and extent of fermentation of feeds in the rumen. Since data obtained with rumen fluid from sheep are often used for dairy cattle, rates and extents of fermentation were compared from cow and sheep rumen fluid. However, since it is often impossible for many industries and schools to retain ruminally fistulated animals, use of fresh bovine faeces as an alternative inoculum was also compared with rumen fluid. Rumen fluid was collected from rumen fistulated sheep and cows kept under the same conditions and, at the same time, fresh faeces were collected from the same cows. Incubations with rumen fluid from cows and sheep resulted in gas productions with comparable profiles. Incubations with sheep rumen fluid and bovine faeces as inoculum resulted in decreased total gas productions, compared with incubations with cows rumen fluid. The correlation between rumen fluid from cows and sheep was high for gas production at 24 and 48 h incubation, calculated maximal gas production (A(m)) and sharpness of the profiles (C-m) (R-2 = 0.90 to 0.96). For rate of gas production (B-m) the correlation between rumen fluid from cows and sheep was lower (R-2 = 0.62). Comparison of gas production profiles from bovine rumen fluid and faeces also resulted in a high correlation for gas production at 48 h incubation and A(m) (R-2 = 0.82 to 0.88), but a low correlation for B-m, C-m, and gas production at 24 h incubation (R-2 = 0.24 to 0.61). Rumen fluid from sheep and faeces from cows can be used as an alternative to rumen fluid from cows to accurately determine differences in total gas production. These alternative inocula, however, did not accurately estimate the rate of gas production (B-m) of different feed samples obtained when incubated with rumen fluid from cows. (C) 2002 Elsevier Science B.V. All rights reserved.