The objective of this study was to evaluate the effect of different true protein:non-protein nitrogen ratios in supplements on intake and ruminal transit and degradation dynamics of neutral detergent fiber (NDF) in grazing cattle during rainy season. Five crossbred Holstein × Zebu steers, averaging 335±35 kg of body weight and fitted with rumen and abomasum canullaes were used. The treatments were: control (only pasture), and supplements based on urea, 2/3 of nitrogenous compounds from urea and 1/3 of nitrogenous compounds from albumin, 1/3 of nitrogenous compounds from urea and 2/3 of nitrogenous compounds from albumin, and albumin. Two hundred grams/d of crude protein (CP) were supplied from supplements. The experiment was carried out according to a 5 × 5 Latin square design, with five 15-day experimental periods. There were no effects of supplementation on voluntary intake, except for CP intake, which was increased by supplementation. The replacement of urea by albumin in the supplements caused linear effect on the CP intake. The intakes of the other diet components were not affected by the supplement composition. There was no effect on ruminal rate of passage of fibrous compounds. Supplementation increased the estimates of common rate of lag and degradation of NDF. However, no effect of supplement composition alteration was observed on this parameter. Supplementation of cattle with rumen degradable (protein or non-protein) nitrogenous compounds for grazing cattle during rainy season does not affect voluntary intake of pasture.
albumin; pasture intake; supplementation; urea
