In vitro effects of birdsfoot trefoil (Lotus corniculatus L.) pasture on ruminal fermentation, microbial population, and methane production

Birdsfoot trefoil (BFT) is a legume containing condensed tannin that does not cause bloat in cattle when freshly grazed. Two of the most outstanding effects associated with condensed tannin include the potential to decrease ruminal protein degradation through binding protein and to reduce ruminal methane (CH4) production. The objective of this study was to investigate the effects of feeding BFT-based diets without or with concentrate supplementation on in vitro ruminal fermentation with a focus on CH4 production in continuous cultures. The current study evaluated the effects of feeding 2 types of forages (orchardgrass vs. BFT) combined with 3 supplements (no supplement, ground barley, and specifically designed mixed ration) on the in vitro rumen microbial ecosystem in a 2 × 3 factorial design with 3 independent runs of continuous cultures. Concentration of ammonia-N decreased when cultures were offered BFT-based diets compared with orchardgrass-based diets (P < 0.01), whereas supplementing ground barley or specifically designed mixed ration did not affect ammonia-N concentration, regardless of type of forage. Neither forage nor supplementation had an effect on the concentration of total volatile fatty acids. Microbial populations of Fibrobacter succinogenes and Ruminococcus flavefaciens decreased when cultures were offered BFT-based diets (P < 0.01). Methanobrevibacter sp. decreased due to feeding BFT-based diets (P = 0.02), but Methanomicrobium sp. was not affected. Adding supplements did not influence methanogens. Methane production was reduced by feeding BFT-based diets (P < 0.01); however, supplementation of ground barley or specifically designed mixed ration led to no effect on methane production, regardless of type of forage. Condensed tannins in BFT exerted anti-microbial properties against cellulolytic bacteria and methanogens in a species-dependent manner, resulting in some positive effects on in vitro ruminal fermentation.