Effect of mixtures of legume species on ruminal fermentation, methane and microbial nitrogen production in batch and continuous culture (RUSITEC) systems

The effect of cicer milkvetch (Astragalus cicer L.) and sainfoin (Onobrychis viciifolia Scop.) on ruminal fermentation, methane production, and microbial nitrogen synthesis was assessed in two experiments. Experiment 1 analyzed 2 legumes, cicer milkvetch and sainfoin at 2 stages (vegetative and late flower) incubated with alfalfa (Medicago sativa) at 5 inclusion rates 0:100; 25:75, 50:50, 75:25 and 100:0 (as DM) in batch culture. Experiment 2 analyzed vegetative cicer milkvetch and alfalfa incubated in ratios of 25:75, 50:50, 75:25 and 100:0 (as DM) in continuous culture systems (RUSITEC). In batch culture, increased dry matter disappearance (DMD), and propionate percentage (%, total), and reduced methane (mg g-1 DMD) occurred with vegetative cicer milkvetch inclusion. In RUSITEC, DMD linearly increased (P < 0.01), acetate:propionate ratio quadratically decreased, while ammonia (NH3-N) concentration (P<0.01) and butyrate percentage (% total) linearly decreased (P<0.05) with increasing inclusion of cicer milkvetch. No differences were observed for methane (CH4) production (mg g-1 DMD), or short chain fatty acid (SCFA) production (mmol d-1). Microbial nitrogen synthesis and efficiency of protein synthesis linearly increased (P<0.05) with increased inclusion of cicer milkvetch. Results suggest cicer milkvetch may result in synchronicity of energy and nitrogen during rumen fermentation, which could enhance cattle production.