Availability of nitrogen (N) limits pasture production. Inclusion of legumes into grass pastures can provide an alternative N source through biological N₂ fixation (BNF), and enhance retention and cycling of soil C and N. Despite the use of alfalfa (Medicago sativa L.), cicer milkvetch (Astragalus cicer L.) and sainfoin (Onobrychis viciifolia Scop.) in grass-legume pastures to improve forage quality, relative BNF potentials and resource partitioning are unknown. We quantified BNF using ¹⁵N isotope dilution and estimated resource partitioning in alfalfa, two cultivars of cicer milkvetch and two cultivars of sainfoin under controlled conditions. Percentage of nitrogen derived from atmosphere followed the order alfalfa (92%) > cicer milkvetch (87%) > sainfoin (81%); corresponding to estimated N contributions of 200, 128 and 65 kg N ha⁻¹ yr⁻¹, respectively, based on total herbage. Root dry matter was 24% to 36% greater than shoot dry matter in all of the legumes, providing substantial below-ground C and N. Cultivars of the same species did not differ in any measured parameter (p > 0.05). Despite the lower BNF in cicer milkvetch and sainfoin compared to alfalfa, their use may not negatively affect stand productivity and C storage.

This article aims to review recent progress and update on utilization of exogenous fibrolytic enzymes in fiber fermentation, degradation, and digestions and nutritive and anti-nutritional characteristics of whole legume faba bean and its silage. The study focused on strategies to improve the utilization and bioavailability of fiber through pre-treating exogenous fibrolytic enzymes. The review includes features of nutrition and anti-nutritional factors and environment impact, forage fiber fermentation, degradation and digestion, legume bean in various diets, use of exogenous enzyme and factor affecting enzyme action in fiber digestion as well as exogenous enzyme response. This review also provides very recent research on effects of fibrolytic enzyme on rumen degradation characteristics of dry matter and fiber of whole plant faba bean silage and effect of exogenous fibrolytic enzyme derived from trichoderma reesei on lactational performance, feeding behavior, rumen fermentation and nutrient digestibility in dairy cows fed whole plant faba bean silage-based diet. This study provides an insight on nutritive and anti-nutritive characteristics of whole legume bean and its plant silage and utilization of exogenous fibrolytic enzymes in fiber fermentation, degradation, and digestions.

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 (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·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.

Cicer milkvetch (CMV; Astragalus cicer L.) is an alternative non-bloat legume to managing alfalfa. A 2-yr study was conducted to compare three CMV cultivars (Oxley II, Oxley, and Veldt) to AC Grazeland alfalfa (ALF; check forage) for nutritive value and animal preference. Each yr, replicate samples (n = 4) of each forage type were harvested late summer and analyzed for nutrient profile. Oxley II had lower (p < 0.05) fiber content than AC Grazeland, while Oxley and Veldt were similar (p = 0.48) to AC Grazeland for neutral detergent fibre (NDF), acid detergent fibre (ADF) and starch. In contrast, Oxley II had higher (p < 0.05) net energy for gain (NEg) than AC Grazeland, and Oxley and Veldt were similar (p > 0.05) to AC Grazeland for NEg. All three CMV varieties had similar levels of total digestible nutrients (TDN) (63.6 ± 0.6%; p > 0.05), but had higher (p = 0.01) energy content than AC Grazeland alfalfa (54.9 ± 1.4% TDN). Selenium (Se) concentrations were similar (p > 0.05) among CVM cultivars and less than 1 mg/kg DM, and no swainsonine or nitrotoxins were detected in the CMV cultivars. The Oxley II CMV tended (p = 0.06) to have a higher (139) relative feed value (RFV) compared to AC Grazeland (94), while Oxley and Veldt had moderate RFV values (128). Dry matter intake of Oxley II, Veldt, and Oxley CMV was 4, 18, and 28% greater than AC Grazeland, respectively. Based on the relative preference index (ratio of forage DMI to AC Grazeland alfalfa DMI), forage types are ranked as follows: AC Grazeland (1.0) < Veldt (1.2) < Oxley (1.4) < Oxley II (1.7). Study results suggest that CMV cultivars harvested late summer, maintained higher forage quality with greater preference compared to alfalfa.