In vitro methane production and tolerance to condensed tannins in five ruminant species

Brazil has the largest commercial herd of ruminants in the world and these animals are kept on tropical pastures with low crude protein and high fibre contents resulting in large amounts of methane emission from rumen microbial fermentation. The main objective of this study was to compare in vitro methane production from taurine dairy cattle (Bos taurus taurus), zebu beef cattle (Bos taurus indicus), water buffaloes (Bubalus bubalis), sheep (Ovis aries) and goats (Capra hircus) fed similar diets. The study also aimed to compare in vitro rumen fermentation characteristics and to investigate the effects of condensed tannins (CT) on methane production among those species. Four roughages were evaluated as substrates: maize silage (Zea mays), fresh elephant grass (Pennisetum purpureum), Tifton-85 hay (Cynodon spp.) and fresh alfalfa (Medicago sativa). Acacia (Acacia molissima) tannin extract was used as an external CT source to raise dietary CT content to 50 eq-g of leucocyanidin per kg of DM. Bovines emitted more methane than small ruminants as measured on a degraded organic matter basis. Condensed tannins mitigated rumen methane emission by inhibiting fermentation but they did not increase microbial decomposition efficiency. Condensed tannins have greater effects in large ruminants than in small ruminants.