Use of essential oil on feedlot diet

The use of additives in beef cattle diet has shown improvement in the performance of feedlot animals, making them a promising alternative to improve efficiency production. By this sense the aim of this study was evaluate the effect of levels of supplementation and additives during growing on pasture and this effect at finish phase on feedlot. Were used in a 60-d trial, 40 young Nellore bulls with initial body weight of 488? 31 kg kept in individual pens. A blend of virginiamycin plus monensin (V+M) or essential oil (EO) was evaluated. Diets were formulated for gain 1.5 kg d^-1 with 30% of roughage (corn silage) and 70% of concentrate. Animals were fed twice-d and orts adjusted to 5% of dry matter provided. The treatments was: T1 - 0.3% BW of supplementation with monensin during growing phase plus V+M in feedlot diet; T2 - 0.3% BW of supplementation with EO during growing phase plus EO in feedlot diet; T3 - 0.6% BW of supplementation with virginiamycin during growing phase plus V+M in feedlot diet; T4 - 0.6% BW of supplementation with EO during growing phase plus EO in feedlot diet. Animals were evaluated for performance, dry matter intake and carcass yields. Weighing at begging and end of feedlot phase with 14 hours of fasting was conducted. Data were analyzed using a completely randomized design in 2x2 factorial arrangements, two diets with two growing historical. Analysis of variance was applied and averages compared by Tukey test (P<0.05), using Proc Mixed of SAS. Animal performance (kg d^-1) do not differ (P= 0.196) between treatments being which T1, T2, T3 and T4 showed gain of 1.56; 1.78; 1.48 and 1.57 kg d^-1 respectively. However, animal that received EO in the diet achieved higher (P= 0.002) dry matter intake T2 -2.27 % BW (12.05 Kg d^-1) and T4 - 2.20 % BW (11.80 Kg d^-1) compared with V+M treatment T1 - 1.96 % BW (10.36 Kg d^-1) and T3 - 2.02 % BW (11.14 Kg d^-1). Feed efficiency do not differ (P= 0.1690) between treatments. The carcass yields was lower (P= 0.004) for animals that received EO and was supplemented with 0.3% of BW during growing 55.8%, probably due to the lower weight in the feedlot input. The blend of V+M provided better efficiency compared with EO treatments.