Ingestive behavior and nitrogenous compounds balance of heifers on pastures of Urochloa brizantha cv. Marandu deferred and fertilized with nitrogen

Abstract

This study has to evaluate the effect of different levels of nitrogen in pastures Urochloa brizantha cv. Marandu deferred, and its implications on feeding behavior and the nitrogen balance of Nelore heifers. The design was used completely randomized, with four treatments (nitrogen of levels) and four replications (number of fertilized paddocks). Were used 16 heifers Nellore, averaging eight months of age and initial body weight of 178.69 ± 26.67 kg, 4 heifers for treatments. The results were evaluated by analysis of variance and regression at 5% probability. The nitrogen levels did not influence the behavioral activities with average time of 576.25 minutes (10:00) grazing, 509.84 minutes (8h50min) in rumination, 315.16 minutes (5h25min) in idle and 39 minutes in the feeding trough. For nitrogen intake, digested nitrogen and the nitrogen retention (g/day) and the digested nitrogen (%N ingested), there was increasing linear effect (P <0.05) due to the nitrogen levels. The nitrogen levels did not affect (P>0.05) nitrogen in the feces and urine nitrogen (g/day), and not the nitrogen retention (% of N ingested) and nitrogen retention (% of digested N), whose mean values were 22.98 g/day; 39.48 g/day; 46.83% and 78.10%, respectively. For N urea in urine, there was increasing linear effect (P<0.05) with an increase of 0.335 ml/dL for every 1 kg of N applied. For N urea in plasma had no effect (P>0.05) of nitrogen rates, averaging 15.79 ml/dL. The behavioral activities of the heifers are not affected by nitrogen levels in pastures Urochloa brizantha cv. Marandu deferred. The ingested nitrogen, retained nitrogen (g/day), digested nitrogen (g/day) (% of ingested N), the urea nitrogen in urine, excretion in urine urea and urea nitrogen in urine are influenced by the amount increasing crude protein forage derived nitrogen adduction, these results are important to prevent the economic losses due to excessive supply of protein in the diet.