PSXI-8 Effects of selected feed additives on feedlot cattle performance when fed diets containing rehydrated corn grain silage during adaptation period

Abstract The ability of some essential oils not to depress dry matter intake (DMI) is recognized, a marked effect when supplementation with sodium monensin is used; favoring DMI in wk 1 in the feedlot has a great impact on ingestive behavior in the subsequent weeks and on average daily gain (ADG) for the total period. The objective of the study was to evaluate performance and feed consumption in the first 30 d of feedlot, using different feed additives. Nelore bulls [n = 48; initial body weight (BWi) = 378.1 kg ± 8.92 kg; 20 mo of age] were used. Bulls were allocated in a collective pen, randomly distributed into two treatments, with the animal being the experimental unit. The treatments were: 1) Sodium Monensin (MON), 26 mg/kg DM; and 2) CRINA + RUMISTAR + Hy-D (CRD), blend of essential oils, 90 mg/kg DM + exogenous α-amylase, 560 mg/kg DM + 25 hydroxy-vitamin D3, 1 mgּ animal-1ּ d-1 . The animals were weighed fasting (± 16h) at the beginning of the experiment and weighed in the fed state on d 31, with 4% shrink deducted to account for the contents of the gastrointestinal tract. DMI was measured daily and individually using electronic troughs with selector doors (Intergado, PONTA, Betim, MG-Brazil), capable of identifying and allowing access to the animals through an earring with a transponder. The adaptation period lasted 15 d, with increasing levels of concentrate inclusion, being 5 d (72% concentrate), 5 d (75.8% concentrate), and 5 d (83.3% concentrate), being that between d 16 and 30 the finishing diet (89.3% concentrate) was offered, consisting of ground corn, rehydrated corn grain silage, cottonseed meal, whole cottonseed, sugarcane bagasse, urea, and vitamin-mineral supplement. The DMI was evaluated in two periods (d 0 to 15 = adaptation; d 0 to 30 = first 30 d). Data were analyzed by SAS PROC ANOVA, using BWi as a covariate when significant. Animals fed CRD had greater BW at d 30 (425 vs 417 kg, P = 0.04) and increased ADG by 0.260 kg/d (1.56 vs 1.30 kg/d, P = 0.04). The DMI at adaptation (7.96 kg/d, P = 0.90), and in the first 30 d (8.67 kg/d, P = 0.33) and in the first 30 d in relation to BW (2.18 % of BW, P = 0.46) were similar between treatments; however, CRD tended to provide a better feed efficiency (0.179 vs 0.153, P = 0.09). These findings suggest that the use of CRD may be an effective strategy to enhance feedlot cattle performance during the adaptation period, when fed diets containing rehydrated corn grain silage.