This study was carried out to evaluate the nitrogen balance, the urea concentrations in urine and plasma and the microbial protein synthesis in heifers fed diets containing sugar cane treated with calcium oxide. Twenty Holstein-zebu crossbred heifers, with average initial body weight of 200 kg were used, distributed in a completely randomized design, with four treatments and five repetitions. The animals were housed in covered individual stalls, with concrete floor, provided with individual concrete trough for feeding and automatic drinkers common for every two stalls. The experimental period was of 21 days, and data collection was performed on the last seven days. The diets were formulated to be isoprotein, with14% crude protein and they contained 71% sugar cane (with 0; 0.75; 1.5 or 2.25% CaO, in natural matter) corrected with 1% of urea and ammonium sulfate (9:1) and 29% of concentrate. Sugar cane was offered to the animals after 24 hours of treatment with chromium oxide. Treatment of sugar cane with calcium oxide affected nitrogen balance by reducing intake and quantity of retained and digested nitrogen. The retained nitrogen (in % of ingested N and digested N) was also linerarly reduced according to increases in levels of calcium oxide in the sugar cane. Use of calcium oxide at levels up to 2.25% in sugar cane treatment does not affect concentrations of urea in the urine and in the plasma neither the urine urea excretion and the microbial protein synthesis in dairy heifers.
microbial purines; nitrogen retention; plasma; whitewash
