Differences in rumen fermentation, methane production, and microbiota of buffalo, cattle, and sheep: an in vitro study

The emission of methane (CH4) from the livestock sector is a particular concern and differences in rumen fermentation pathways lead to a variation in CH4 production among ruminant species. The present in vitro study evaluated the fermentation characteristics and CH4 output of rumen fluid from three different donor species (buffalo, cattle, and sheep) under standardised experimental conditions across three laboratories, using a randomised rotation scheme based on a 3 × 3 Latin square design. After 48 h of incubation, differences were observed in the main fermentative traits with appreciable differences among donor species in protozoa count, dry matter degradability, and volatile fatty acid profiles. Gas production was influenced by species with sheep and buffalo recording comparable values approximately 12% higher than cattle gas production. Instead, the CH4 concentration was higher in sheep than buffalo (25.2 vs 21.9%, p < 0.05) with intermediate values for cattle (23.6%). Gas and methane production were monitored continuously and data collected were fitted with the Groot model. This approach highlighted differences in fermentation rate both for gas and CH4 in the species considered. In both cases, sheep rumen fluid was characterised by the shortest time to reach the maximum (less than 1 h compared to 2–5 h in the other species) while the maximum fermentation rate was comparable to cattle’s. Variations were also detected in rumen microbiota, with differences in alpha and beta diversity and core microbial composition. The relevant findings reached with the study of CH4 production kinetics demonstrate the species-specific differences in fermentation processes.