Two experiments were carried-out to study the effects of concentrate rations containing 0, 4, 7, and 10 % bovine tallow on total digestibilities of dry matter (DM), organic matter (OM), ether extract (EE), crude protein (CP), neutral detergent fiber (NDF), total carbohydrates (TC), calcium (Ca), and phosphorus (P); partial digestibilities (CDAp) of DM, OM, EE, CP, NDF, and TC, and the potential and effective "in situ" degradability of DM and CP of the corn silage and concentrates. In the first experiment the total digestibilities for DM, OM, EE, NDF, CP, Ca, and P was not influenced by treatments; however, tallow significantly reduced the digestibility of TC. In the second experiment, the total digestibilities of DM, OM, NDF and TC decreased. There was reduction in ruminal digestion of the OM, CP, TC, and NDF expresed as % of total ingested. Tallow increased the OM and TC intestinal digestibilities. There was no suggestive differences in DM and CP potential and effective degradability. Numericaly, the digestion rate was higher for the treatment containing 10 % of tallow.