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 two legumes, cicer milkvetch and sainfoin at two stages (vegetative and late flower) incubated with alfalfa ( Medicago sativa) at five 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 (NH 3 -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 (CH 4 ) production (mg·g −1 DMD), or short chain fatty acid (SCFA) production (mmol·day −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.