Comparison of cold resistance and nutritional quality of six tropical and subtropical leguminous forages during overwintering period

To select suitable high quality green forage for winter season in Southern China, the cold resistance and nutritional qualities of six tropical and subtropical leguminous forage species including Desmodium intortum, D. laxiflorum, D. heterocarpum, D. reticulatum, D. heterocarpum var. strigosum and Stylosanthes guianensis grown in Guangzhou during the overwintering period were compared. The results showed that all species could maintain green leaves in winter except S. guianensis, and the chlorophyll contents of D. intortum and D. laxiflorum were significantly higher than those of the other four species (P<0.05). Further, D. intortum had the highest net photosynthetic rate (P<0.05), followed by D. laxiflorum. Hence, these two forages were considered to have a stronger cold resistance than others. During winter season, compared with the other species, D. intortum had a higher nutritional value because of its higher crude protein content (15.99%~20.26%) (P<0.05) and lower detergent fiber (neutral detergent fiber, NDF: 27.92%~30.89%, acid detergent fiber, ADF: 23.96%~27.06%) and condensed tannin content (6.05~11.95 mg·g-1) (P<0.05). Therefore, in Southern China, D. intortum can potentially be used as a preferred leguminous green fodder in winter.