Interseeding sainfoin with alfalfa offers early‐season increase in forage production

Alfalfa ( Medicago sativa ) is a widely cultivated forage legume valued for its high forage mass and nutritive value but is often associated with pasture bloat in ruminants. Interseeding alfalfa with sainfoin ( Onobrychis viciifolia ), a tannin‐rich legume known for its anti‐bloating properties and environmental benefits, has emerged as a potential solution. A 2021–2023 field trial evaluated the impact of interseeding alfalfa with sainfoin on forage mass, nutritive value, and condensed tannin (CT) concentration near Cedar City, UT. Two treatments, alfalfa monoculture (Mono) and alfalfa–sainfoin mixture (Mixed), were established in 2021. In the establishment year, the mixed system showed a roughly 10% forage mass advantage compared to Mono, though no consistent difference was observed in subsequent years. Forage nutritive value parameters were primarily influenced by cutting time and seasonal variation rather than treatment. Despite limited treatment differences, crude protein, relative feed value, relative forage quality, and total digestible nutrients values in both systems consistently met USDA criteria for “supreme” quality hay. CT concentrations varied significantly by treatment, year, and cutting. Notably, in 2022, the mixed system showed substantially higher CT concentrations during early cuttings compared to the monoculture alfalfa (0.823% vs. 0.20% in the first cutting and 0.47% vs. 0.25% in the second cutting), indicating that sainfoin can meaningfully enhance forage CT concentration when well‐established, but not consistently. These findings suggest that interseeding sainfoin may offer early‐season benefits in both forage mass and bloat‐mitigating potential, though year‐to‐year variability and cutting stage may influence overall forage value.