CHARACTERIZATION OF PROTEOLYSIS IN ALFALFA AND RED-CLOVER

The loss of protein (proteolysis) during the ensiling of forage legume s is a severe problem. Alfalfa (Medicago sativa L.) will lose 44 to 87 % of its protein during ensiling, whereas red clover (Trifolium praten se L.), a legume of similar protein content, will lose only 7 to 40%. Reasons for this difference in proteolysis are unknown. Research was c onducted to determine and compare the general characteristics (rates, pH and temperature effects) of proteolysis in red clover and alfalfa e xtracts, and secondly to evaluate different in vitro test proteins to monitor legume proteolysis. Proteolytic rates of alfalfa and red clove r extracts were not significantly different when either ribulose 1,5-b isphosphate carboxylase/oxygenase (RubisCo) of bovine serum albumin (B SA) was used as the protein substrate; however, both legumes displayed significantly higher rates for the degradation of RubisCo than BSA (P < 0.10). The pH optima were 5.5 for both legumes when RubisCo was deg raded, and 5.5 and 6 for alfalfa and red clover, respectively, when BS A was the substrate. Proteolysis in the legume extracts had similar pH and temperature stabilities and temperature optimum for the degradati on of RubisCo. These data suggest that alfalfa and red clover have sim ilar inherent proteolytic activity and cannot explain the difference i n extent of proteolysis in the two silages.