Two experimentswere conducted aiming to evaluate the effect of amounts of supplement on theintake, digestibility, body weight gain and microbial synthesis efficiency inbeef cattle. Four Holstein-Zebu steers fistulated in the esophagus, rumen andabomasum with an average of 250 kg of body weight were used in experiment 1.The supplement was made up cottonseed meal, ground corn grain, mineral mixtureand urea/ammonium sulfate. The diets were: control (salt) and supplements levelsof 0.33, 0.66 and 1.00% of body weight (BW). Maximum intake of dry matter (DM),neutral detergent fiber (NDF) and total digestible nutrients (TDN) were estimatedat 1.09, 0.73 and 1.20% of BW, respectively. It was observed a linear intakeincrease to organic matter (OM), crude protein (CP), ether extract (EE) andnon-fiber carbohydrates (NFC) intake as supplement offer increased. The totaldigestibility from DM, OM, CP, EE and NDF increased linearly with the intakeof supplement but no affected on microbial efficiency. Nineteen Zebu steersaging 18 months and mean body weight of 320 kg were used in experiment 2. Thediets were: maintenance, control (salt), and the daily supplement offer of 1,2 and 3 kg. It was observed linear increase in DM, OM, CP, EE, NDF and NFC intakeas supplement offer increased. Maximum intake of TDN, diet TDN content and averagedaily gain (ADG) were estimated to occur as 2.88, 2.62 and 2.69 kg of supplementoffer, respectively. A quadratic effect was observed for total digestibilityin all diet components. The microbial efficiency was not influenced by dietsupplementation. The neutral detergent fiber digestibility is highest for aintake of approximately 1.5 kg of the supplement/day, which results in the bestresponse to the ADG obtained with the intake of 400 g of CP.
