The objective of this experiment was to evaluate the effects of the concentrate level in the diets on the intakes and total and partial apparent digestibilities of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and total carbohydrates (CHO). The effect of collections carried out during the day and the night, for the DM and OM total and partial apparent digestibilities, was also evaluated. Four Nellore bulls, fistulated in the rumen, abomasum and ileum, fed diets ad libitum with 25.0; 37.5; 50.0; 62.5; and 75.0% of concentrate, were randomly allotted to a completely randomized block design. The chromium oxide was used as indicator, in the dose of 20 g/day. The intakes of DM, OM, total digestible nutrients (TDN) and EE increased and that of NDF decreased linearly with the increase of the concentrate in the diets. The minimum estimated total apparent digestibilities of 67.27% for DM and 68.31% for OM were with 36.71 and 41.5% of concentrate in the diets, respectively. The ruminal apparent digestibilities of DM and OM averaged 63.35 and 71.42%, respectively. The increase of concentrate in the diets reduced the ruminal digestion of NDF, but resulted in linear increase in TDN and total DM digestibility of the diets. There were no differences for the total and partial apparent digestibilities of DM and OM obtained in collections accomplished during the day or the night
bulls; concentrate; digestibility; intake
