Propionic acid bacteria enhance ruminal feed degradation and reduce methane production in vitro

Thirty-one strains of propionic acid bacteria were screened for their effects on methane production and volatile fatty acid concentrations using in vitro assays of rumen fluid from Norwegian dairy cows and a grass silage–concentrate mixture as substrate. Nine of 31 strains were further analysed for effects on substrate degradation. Propionic acid bacteria led to reductions of up to 20% in methane production. Seven strains stimulated volatile fatty acid production, and in their presence in vitro substrate degradation tended to increase (P < .10). Most consistent results were found with Propionibacterium thoenii T159, which reduced methane production by 20% and caused 8% and 21% overall increases in substrate degradation and total volatile acid production, respectively (P < .05). Concomitant beneficial effects of a reduction in methane emissions and an increase in feed degradation suggest that this strain may be a promising tool for improving the productive performance of dairy cows.