Effect of phosphorus supplementation on nutrient intakes and dry matter digestibility by Nellore steers in a feedlot under Brazilian conditions

The indiscriminate use of P in feedlots of Brazil is still common and the consequences need to be investigated. The reduction of P levels in feedlot diets in Brazil may be an important strategy to increase the economic and environmental sustainability of finishing cattle in these systems. Thus, we evaluated the effects of phosphorus supplementation on nutrient intakes and dry matter digestibility. Forty-two animals with an initial body weight of 296 ? 25 kg, were distributed in a completely randomized design consisting of 3 treatments and 14 replicates. The diet, on a dry matter (DM) basis, was comprised of sugarcane bagasse (200 g/kg) plus concentrate (800 g/kg). The concentrate had 474.0 g/kg ground corn, 88.0 g/kg soybean meal, 216.0 g/kg citrus pulp and 8.0 g/kg urea and were balanced for approximately 130 g/kg of crude protein (DM basis). The treatments were without supplementary P (T₁), commercial mineral supplement specific for feedlot cattle (T₂) and dicalcium phosphate (T₃) with 2.4, 4.2 or 5.0 g/kg P on a DM basis, respectively. The variables were analyzed as a completely randomized arrangement using GLM procedure of SAS. The estimated 95% confidence intervals (95% CI) were presented as follows: ?x ? ((U - L)/2); Where ? is the mean of a variable, x; and U and L are the upper and lower limits of the 95% confidence interval, respectively. The DM, crude protein (CP) and neutral detergent fiber assayed with a heat stable amylase and expressed inclusive of residual ash (aNDF) intakes and dry matter digestibility (DMD) were similar between the groups with or without phosphorus supplementation (P > 0.05). Under Brazilian conditions, feedlot beef cattle fed high grain diets do not require P supplements. Phosphorus levels of approximately 2.4 g/kg in DM, as used in the control diet, appears adequate. Lower values may also be appropriate but were not tested here. Phosphorus supplementation did not affect the nutrient intakes and DMD.