Effects of Tannin-Rich Forages (Lespedeza bicolor and Polygonum viviparum ) Mixed With Medicago sativa on In Vitro Rumen Fermentation.

Ruminant production is currently facing many challenges, and thus it is essential to develop native sustainable feed resources. Alfalfa (Medicago sativa ) is a high-quality legume forage, but its rapid degradation in the rumen leads to bloating and more urine and methane production, resulting in nitrogen waste and environmental pollution. Mixing alfalfa with tannin-rich forages is an effective way to improve rumen fermentation. Therefore, to utilize tannin-rich forages such as Lespedeza bicolor and Polygonum viviparum as a partial replacement for alfalfa in the feed, three in vitro fermentation experiments were performed. In Experiments 1, 2, and 3, L. bicolor leaves, P. viviparum leaves, and P. viviparum bulbils were mixed with alfalfa at different ratios (0:100, 20:80, 40:60, 60:40, 80:20, and 100:0), respectively. Gas and methane production, fermentation parameters (pH, ammonia, microbial protein, and in vitro dry matter digestibility), and volatile fatty acid concentrations were determined to elucidate the effects of forage mixing on rumen fermentation. L. bicolor showed a more prominent effect on reducing gas and methane production than P. viviparum when mixed with alfalfa. When the mixing ratio of tannin-rich forages and alfalfa was below the threshold of 40:60, the overall fermentation of the mixed substrates was improved compared to that of alfalfa alone. These findings will support the application of L. bicolor and P. viviparum in ruminant diets to improve practical livestock production and provide a specific forage use strategy in arid and semiarid grasslands and alpine meadows.