Source and Implications of Elevated Non-Fibrous Carbohydrates in the Perennial Legume Birdsfoot Trefoil (Lotus corniculatus L.).

While dairy-quality alfalfa hay has nearly ideal levels of protein and fiber to support milk production, its nutritive value is limited by available energy, which is measured as the non-fibrous carbohydrate (NFC) concentration. In a study comparing 14 birdsfoot trefoil cultivars with two alfalfa cultivars, the non-fibrous carbohydrate concentration of birdsfoot trefoil was 20% greater than alfalfa, averaging 390 g kg^-1 DM while alfalfa averaged 320 g kg^-1 DM. In a study that compared Angus steers finished in the feedlot with steers finished on irrigated meadow bromegrass or birdsfoot trefoil pastures, mean birdsfoot trefoil NFC was 398 g kg^-1 DM while NFC of the concentrate diet was 427 g kg^-1 DM and NFC of meadow bromegrass pasture was 193 g kg^-1 DM. The neutral detergent fiber (NDF) concentrations of the concentrate, birdsfoot trefoil and meadow bromegrass diets were 310, 289 and 504 g kg^-1 DM, respectively. As a result of these diets, the carcasses of birdsfoot trefoil-finished steers had a greater dressing percentage and more fat than carcasses of grass-finished steers. In a consumer sensory panel comparing ribeye steaks from grain-, birdsfoot trefoil- and grass-finished steers, the flavor and tenderness of steaks from birdsfoot trefoil-finished steers were comparable to steaks from grain-finished steers and preferred to steaks from grass-finished steers, while the ratio of omega-6 to omega-3 fatty acids (n-6:n-3) in the fat of steaks from birdsfoot trefoil-finished steers was comparable to the n-6:n-3 of steaks from grass-finished steers. Numerous studies have demonstrated greater stem digestibility and greater ruminant intake and productivity on birdsfoot trefoil than on alfalfa. We hypothesize that differences observed in the lignification of stem fiber cells from birdsfoot trefoil and alfalfa may explain the greater NFC concentration and the greater productivity of ruminants fed birdsfoot trefoil compared with ruminants fed alfalfa.