Phosphorus supplementation with or without other minerals, ionophore and antibiotic did not affect performance of Nellore bulls receiving high-grain diets, but increased phosphorus excretion and dietary costs

Abstract

This study was conducted to evaluate the effect of phosphorus (P) supplementation, with or without addition of other minerals, ionophore and antibiotic, on performance, P utilisation and profitability in finishing Nellore bulls in a feedlot. Forty-two animals, with an initial bodyweight of 296 ± 25 kg, were distributed in a completely randomised design consisting of three treatments and 14 replicates. The treatments were without P supplementation (T1), commercial mineral supplement specific for feedlot cattle (T2) and supplementation with dicalcium phosphate (T3). The T3 was formulated to achieve a P concentration similar to that of T2, but without adding other additives (e.g. vitamins, ionophores, yeast and chelates) in the mineral mix. The P concentrations were 2.4, 4.2 or 5.0 g P/kg of dry matter (DM), respectively, for T1, T2 and T3. The diet, on a DM basis, comprised sugarcane bagasse (200 g/kg) plus concentrate (800 g/kg). The DM, crude protein and neutral detergent fibre intakes and apparent DM digestibility were similar among the three treatments (P > 0.05). Despite the numerical difference on P concentration in T2 and T3 treatments, P intakes were similar in these treatments. The addition of commercial mineral supplement specific for feedlot cattle or dicalcium phosphate in diets increased P excretion in the faeces and urine, increased P retention and reduced the profitability of the feedlot. Performance and carcass traits were not affected by diet P concentrations (P > 0.05). The profit per head in T1 treatment was US$13.7 and the addition of the dicalcium phosphate and mineral mix in T2 and T3 did not result in profit, these treatments gave economic losses of US$6.80 and US$6.20 per head, respectively. Under Brazilian conditions, feedlot Nellore cattle fed high-grain diets do not require any additional mineral supplements. P concentration of 2.4 g/kg DM, as used in the control diet, was adequate to ensure animal performance and reduce faecal P excretion, which is in agreement with NRC and CSIRO recommendations. Lower values may also be appropriate, but were not tested here.