Balanço de nitrogênio em cordeiros alimentados com rações contendo diferentes teores de concentrado

Evaluated the nitrogen intake, fecal and urinary nitrogen production and nitrogen balance (NB) in lambs fed levels increasing of concentrate (20.0%, 40.0%, 60.0% and 80.0 %) in the southwestern region of Mato Grosso. Were used four lambs mongrel (SRD), intact, with body weight (BW) averaged 19.3 +/- 2.1 kg allocated to metabolism cages, fed twice daily, the concentrate was composed of ground corn and soybean and roughage utilized was corn silage. Were used a design in latin square 4X4, the leavings, faeces and urine were collected daily for six days, in each collection period. Each experimental period lasted 20 days. Intake data of nitrogen (N), fecal N, urinary N, absorbed N and NB expressed in g day (-1);% of nitrogen intake (NI) and grams per kilogram of metabolic weight (g kg(0,75) (-1)) were undergo analysis of variance (ANOVA) and tested using regression equation at 5% probability. It was observed that the inclusion of different levels of concentrate supplied the lambs, on the intake N, N absorbed and urinary in g day (-1), g kg(0.75) (-1) and % NI presented a quadratic effect (P<0.05) with the maximum point obtained for the inclusion of 40.0% concentrate on experimental diets. For fecal nitrogen in g day (-1), g kg0.75 (-1) and % NI and nitrogen balance (NB), the inclusion of concentrate in the diet changed (P<0.05) linearly decreasing with better results for inclusion levels of 20.0% to 40.0% concentrate diet. Thus, it is concluded that the level of 40.0% concentrate in the diet of lambs provides the best values of nitrogen intake, urinary nitrogen and nitrogen absorbed in g day (-1), g kg(0.75) (-1) and in % of nitrogen intake, and provide satisfactory results for the values of fecal nitrogen and nitrogen balance expressed in g day (1), g kg(0.75-1) and in % of nitrogen consumed.