PSXII-33 Effects of feed additives on performance of yearling bulls fed high forage diet

Abstract The aim of this study was to compare the effects of three additives (narasin, lasalocid, and virginiamycin) on the performance of bulls fed a high-forage diet. One hundred and sixty Nellore (Bos indicus) yearling bulls were assigned to a randomized completed block design, according to initial BW (212.5 kg ± 3.1; 10 pen/treatment; 4 animals/pen). Yearling bulls were fed daily and diets were composed of 96% of coastcross haylage (12% CP) and 4% of concentrate, used as the delivery vehicle for the additives. Once a day, the concentrate and forage were offered separately. The forage was offered after the entire consumption of the concentrate. The experimental diets consisted of CON: Control (no additives); NAR: 13 ppm of narasin; LAS: 20 ppm of lasalocid; and VIR: 20 ppm of virginiamycin. The experimental period lasted 140 d and the yearling bulls were individually weighed at d 0, 28, 56, 84, 112 e 140 after 14h of feed and water restriction. The orts were recorded to determine the DMI. Data were analyzed as repeated measures over time using the MIXED procedure of SAS and the LSMEANS option was used to generate individual means. There was a treatment effect on DMI (CON: 5.26b: NAR: 5.69a; LAS: 5.16b; VIR: 5.11b kg/d; SEM = 0.14; P = 0.03), ADG (CON: 0.451b; NAR: 0.557a: LAS: 0.498ab; VIR:0.459b kg; SEM = 0.03; P = 0.04), FE (0.080c, 0.095a, 0.092ab and 0.085bc; SEM = 0.0044; P = 0.05) and final BW (CON: 273.9b; NAR: 287.8a; LAS: 277.1b; VIR: 275.7b kg SEM = 3.4; P = 0.03). In conclusion, the inclusion of 13 ppm of narasin improves the performance of yearling bulls fed high-forage diets.