Performance and Photosensitization of Cattle Related to Forage Quality of Four Legumes1

Abstract

Alfalfa (Medicago sativa L.) is a superior forage legume that has several shortcomings as a pasture species, including ruminant bloat potential. Our objective was to determine whether palatability differences among alfalfa and three nonbloat‐inducing alternative legume species would influence performance of grazing heifers (Bos taurus). Heifer performance was quantified on pure stands of the four legumes from 1982 through 1984 and of three legumes in 1985. Grazing pressure was controlled in pastures that had a Waukegan silt loam (fine‐silty over sandy, mixed, mesic Typic Hapludolls) soil. Heifers confined to cicer milkvetch (Astragalus cicer L.), by far the least palatable species, usually gained less than those confined to either alfalfa, birdsfoot trefoil (Lotus corniculatus L.), or sainfoin (Onobrychis viciifolia Scop.). Mean average daily gains during 1983 and 1984 (long‐term grazing seasons) were 0.67, 0.81, 0.80, and 0.42 kg for alfalfa, birdsfoot trefoil, sainfoin, and cicer milkvetch, respectively. Measurements of nutritive value did not explain gain differences, but reduced intake and frequent photosensitization occurred in heifers that grazed cicer milkvetch. Heifer product per hectare was influenced more by daily gains than by legume carrying capacity. Birdsfoot trefoil is a promising alternative pasture legume because it provided excellent heifer gains and had better summer growth and persistence than sainfoin, although somewhat less persistence than alfalfa. The poor palatability of cicer milkvetch was associated with reduced intake, reduced gains by cattle, and possibly with the photosensitization problem; however, its excellent yield, persistence, and nutritive value indicate that cicer milkvetch deserves more research and breeding to overcome its antiquality traits.