This trial aimed to evaluate the blood parameters and growth of Nellore young bulls finished in pasture in the rainy season supplemented with monensin (MON), virginiamycin (VM) or both associated. Ninety animals were used with the initial BW of 360 kg ± 24.98 kg, receiving daily supplementation in 0.3% of BW, distributed in 12 paddocks of Brachiaria brizantha ‘Xaraés’, with about 2 ha each (3 paddocks/treatment) and fed daily with supplement without additives (SUP), with MON (SUPM - 80 mg/kg), with VM (SUPV - 150 mg/kg) and supplement with MON and VM (SUPMV - 80 and 150 mg/kg, respectively). Supplements had 25% of CP. After 14 d of adaptation, 8 animals were slaughtered as a reference group to obtain the initial dressing percentage (DP) to calculate the carcass gain (CG) at the end of the experiment. The remaining animals (n = 82) were allotted in paddocks (7 animals/paddock). In one paddock were allotted 5 animals, due to the smaller size of the area. Blood was collected after 14 h withdrawal period from feed and water at the 0, 63 and 118 d of feeding. To obtain the ADG, animals were weighted in shrunk. Animals were slaughtered after 140 d of trial. Data were analyzed using the Proc Mixed of SAS with a randomly design (5% of probability). The inclusion of additives in supplements does not affect the insulin (P = 0.81) and glucose (P = 0.29) concentrations. The inclusion of the additives in supplements does not affect the final BW (P = 0.11), hot carcass weight (P = 0.45), DP (P = 0.14) and CG in relation the ADG (P = 0.91). However, the ADG was affected (P = 0.03) by inclusion of additives in supplements. Young bulls fed SUPM had similar ADG (0.867 kg/d) in relation young bulls fed SUPV (0.896 kg/d), but lower ADG than animals fed SUP (0.949 kg/d) and SUPMV (0.969 kg/d). Animals fed SUPV had similar ADG than animals fed SUP, but lower than animals fed SUPMV. The inclusion of MON, VM or both associated in supplements to fed bulls in pasture at the rainy season not promotes additional weight in carcass or BW.