IN-SITU DISAPPEARANCE OF INDIVIDUAL PROTEINS AND NITROGEN FROM LEGUMEFORAGES CONTAINING VARYING AMOUNTS OF TANNINS

In situ degradability of N and proteins were studied in one cultivar o f alfalfa and red clover and two cultivars each of birdsfoot trefoil a nd sericea lespedeza. Concentrations of tannic acid equivalents (perce ntage of DM) were 0.68 in one cultivar of birdsfoot trefoil and 1.77 a nd 2.78 in the two cultivars of lespedeza. The other forages contained essentially no tannins. Forage samples were digested in situ for 0, 2 , 4, 6, and 12 h. The amount of N remaining at 12 h was positively cor related with concentrations of tannin. About 38% of the N remained aft er 12 h in forages with no or low concentrations of tannins, and 86% r emained in the two cultivars of lespedeza. Total electrophoretically i dentified proteins followed similar trends, but the percentage remaini ng was less than that for N. For all forages, bands were found at mole cular masses of 15, 30, 45, 47, and 54 kDa. The percentage of 54-kDa p rotein that remained after 12 h was less than that for the other four proteins (23% vs. 37%). No interaction was found between forage cultiv ar and protein species. These results showed that tannins reduced rumi nal degradation of proteins and that specific forage proteins degraded at different rates that were independent of tannin concentration.