A high ruminal protein degradation is especially undesirable in high producing dairy cows and beef cattle, since these animals have high requirements of protein and the amount of protein that is not degraded by ruminal microorganisms and therefore enters the small intestine (so-called UDP = undegraded protein) is crucial. In this study, Merino rams with ruminal fistulas were used (n = 4) to determine the effect of glucose treatment of soybean meal (SBM), full fat soybean (FFSB) and soybean seed (SBS) on the ruminal degradability of dry matter (DM) and crude protein (CP). All these feedstuffs were grinded, diluted with water and heated (2 h; 100 degrees C) either without or with supplementation of 2 or 3% glucose (20 or 30 g glucose per kg dry feed). For the determination of the ruminal degradability nylon bag technique was used (incubation times: 2-48 h). In general ruminal degradability of protein in all three soy products was reduced by glucose treatment. In FFSB CP disappearance started to decrease after 8 h of incubation, whereas in SBM (+ 3% glucose) and SBS (+ 2 or 3% glucose) reduction of CP disappearance were time-independent. Further, effective degradability (Pe) of DM and CP of all feedstuffs were significantly reduced by glucose treatment, with the reduction being more pronounced when the glucose level was increased. When adding 3% of glucose, the Pe for CP was reduced by 6 (FFSB), 16 (SBM) and 18% (SBS), respectively. Explanation for the observed effects of a glucose supplementation (incl. water and heat treatment) is the reductive activity of glucose within these conditions.