EFFECT OF HEAT OR FORMALDEHYDE TREATMENT ON THE RUMEN DEGRADABILITY AND INTESTINAL-TRACT APPARENT DIGESTIBILITY OF PROTEIN IN SOYBEAN-MEAL AND IN RAPESEED MEALS OF DIFFERENT GLUCOSINOLATE CONTENT

Three Hereford X Friesian/Holstein heifers were each fitted with rumen and simple T-piece duodenal cannulae. They were used in an experiment of latin square design to study the rumen degradability and intestina l apparent digestibility (using the mobile dacron bag technique) of pr otein in soya-bean meal (SBM) and in low and high glucosinolate rapese ed meals (LgsRSM and HgsRSM, respectively) each in untreated (UT), hea t treated (HT) and formaldehyde treated (FT) forms. For rumen incubati on times of 24 h there were no significant protein source X processing treatment interactions for either degradability of protein in the rum en (dgN) or for the proportion of food protein undegradable in the rum en and digestible in the small intestine (DUDN). At this time dgN valu es for FT, HT and UT were 0.263, 0.374 and 0.418 (SEM 0.0078; P < 0.00 1) respectively and DUDN values for SBM, LgsRSM and HgsRSM were 0.320, 0.348 and 0.386 (SEM 0.0078; P < 0.001) respectively. Compared with U T, and to a lesser extent HT, FT at all times after 0 h incubation sig nificantly decreased dgN values and increased DUDN values for all thre e protein sources. Compared with UT, RT significantly decreased dgN. A pparent digestibility of the protein of SBM in the intestines was grea ter than that of LgsRSM and HgsRSM, and overall the values of availabl e undegraded protein for FTLgs and HgsRSM, but not of FTSBM, were simi lar to or greater than for the UT sources. FT tended to decrease the t otal tract apparent digestibility of the protein sources.