PSXII-38 Effect of crude protein sources on feedlot performance and carcass traits of Nellore young bulls

Abstract

Abstract In this trial, 120 Nellore young bulls of ± 386kg kg initial weight were used to evaluate the effect of different sources of crude protein on the feedlot performance (finishing phase) and carcass characteristics. Animals were maintained in fifteen pens for 105 days. Animals were individually weighed and blocked by initial body weight. Pens within a block were randomly assigned to one of three treatments: (D14) Control diet including 14% of crude protein (CP) on dry matter; (D12) Inclusion of 12.5% CP/dry matter and (D11), inclusion of 11% of CP/dry matter. Feed offered was monitored daily as well as feed refusals were collected and weighed to determine the DMI and feed efficiency (F:G). Animals were weighed every 28 d after 16 h feed withdrawal for calculating ADG. The D14 and D12 treatments increased the final weight (P = 0.008) when compared to D11 (564.13; 550.96 and 529.73 kg, respectively). The D14 treatment increased the ADG (1.69 kg; P = 0.002) when compared to D12 (1.54 kg) and D11 animals (1.35 kg). The same was observed for DMI (P = 0.001) (10.40kg, 9.77kg e 8.68kg, respectively) and % BW (P = 0.001), when D14 had the greatest value (2.2%), and D11 the worst (1.90%). There were no effect of the treatments for F:G (P = 0.202). Hot carcass weight was increased by the D14 treatment (P = 0.006) (311.97kg; 300.55 and 289.30kg, respectively). However, the cooling losses were not affected (P = 0.0843), as well as were observed for dressing (P = 0.089). Nevertheless, the carcass daily gain was improved by the D14 (P = 0.02), with animals increasing 1.13 kg/d; D12 with 1.01kg/d and D11, 0.91 kg. In conclusion, the sources of crude protein can affect the feedlot cattle performance, in agreement with the Brazilian Nellore requirement program (Br-Corte). However, in this trial, diets with 14% of CP improved the animal’s performance.