THE DEGRADABILITY OF LEGUME SEED MEALS IN THE RUMEN - EFFECT OF HEAT-TREATMENT

The extent and rate of degradation of dry matter and nitrogen in ground seeds of pea (Pisum sativum), lupin (Lupinus albus var. multolupa), field bean (Vicia faba var. minor), vetch (Vicia sativa) and bitter vetch (Vicia ervilia), previously autoclaved (A) or not (NA) at 120-degrees-C for 30 min, was measured using nylon bags incubated in the rumen of wethers fed lucerne hay. The fractional outflow rate of the legume seed meal particles was determined with chromium as a marker. More than 88% of the protein in untreated legume seed meals, except for vetch, disappeared from the bags by 24 h. Autoclaving decreased both the soluble fraction and the fractional rate of protein degradation of the slowly degraded fraction (P < 0.01). Rumen outflow rate was, respectively, 0.0154 h-1 and 0.0222 h-1, at 0.7 times and 1.0 times maintenance level. Effective degradability of protein was strongly reduced by heat treatment in pea and lupin seeds, moderately decreased in field bean and bitter vetch and almost unchanged in vetch seed meal.