The objective ofthis work was to evaluate the effects of supplementation with nitrogenous compoundson intake and digestibility in cattle under grazing during dry season. It wasused five Holstein × Zebu steers with average initial live weight of 236kg, kept in five Brachiaria decumbens Stapf. paddocks (0.34 ha). Theexperiment was carried out according to a 5 × 5 Latin square design, withfive supplementation levels and five experimental periods. The supplementationlevels were the following: 0; 0.35; 0.70; 1.05, and 1.40 g of crude protein/kglive weight. A mixture of urea, ammonium sulfate and albumin (4.5:0.5:1.0, respectively)was used as nitrogen supplement. The average crude protein levels in the dietwere 7.39; 8.92; 10.98; 12.55; and 13.62%, as dry matter basis, for the respectivesupplementation levels. Linear-response-plateau relationships were observedbetween intake estimates and diet crude protein levels. The linear-response-plateaupattern showed that intake was increased up to crude protein levels close to9%, as dry matter basis. The estimates became unchangeable from this level.The total and ruminal digestibility coefficients of dry matter and neutral detergentfiber, and diet level of total digestible nutrients presented a positive linearpattern according to diet crude protein levels. The rumen ammonia nitrogen concentrationwas linearly increased by diet crude protein levels. This variable assumed thevalue of 8.00 mg/dL when the intake estimates reached the maximum values. Supplementationwith nitrogen compounds in quantities that raise the crude protein content inthe diet to levels close to 9% optimizes the use of low-quality forage by cattleunder grazing.
