INITIAL RATES OF DEGRADATION OF PROTEIN-FRACTIONS FROM FRESH, WILTED,AND ENSILED ALFALFA

Initial rates of in vitro degradation of alfalfa proteins were studied . Fresh, 24-h wilted, and ensiled forages were homogenized before anal ysis for total proteins. Some of the homogenates were fractionated by differential solubility in 10 and 40% ammonium sulfate, followed by ul trafiltration of the 40% salt-saturated solution. The protein fraction s obtained were chloroplast membrane proteins (fraction 3), soluble pr oteins from plant cell cytoplasm and the chloroplast (fraction 2), and proteins remaining soluble in the extracted 40% salt-saturated soluti on (fraction 2B), respectively. Total and fraction 3 silage proteins w ere degraded faster than the respective fresh and wilted proteins. The re were no treatment effects on the rates of degradation of the solubl e proteins of fractions 2 and 2B. Protein fractions from fresh and 24- h wilted alfalfa degraded, from greatest to least, in the following or der: fractions 2, 2B, and 3. Degradation rates for fractions 2 and 2B of ensiled forages were similar but greater than that of fraction 3. A lfalfa proteins were degraded rapidly in die rumen, and soluble protei ns were degraded faster than the chloroplast membrane proteins. Ensili ng of alfalfa increased the rate of degradation of chloroplast membran e proteins, but neither wilting nor ensiling affected degradation rate s of the soluble protein fractions 2 and 2B.