Abstract
Weaning and transport represent a high stress time for calves. Preconditioning (PC) by weaning before the transport separate these stressors. The stressors generate oxidative stress, which can be reduced by mineral and vitamin supplementation (MVS) with an antioxidant capacity. Our objective was to evaluate the effect of PC and MVS on performance of steers. The experiment used a 2 × 2 factorial arrangement design, considering a 26-d PC treatment from weaning to transport to the feedlot (d 0); and injectable MVS on d -45, -26, and 0. The MVS consisted of Cu, Zn, Mn, Se, vitamin E (0.2, 0.8, 0.2, 0.1, and 1 mg/kg body weight (BW), respectively), and vitamin A (1190 IU/kg). Sixty Angus-crossbred steers (186.4 ± 27.6 kg) were randomly assigned to the four treatments (MVS+PC; N+PC; MVS+N; N+N; n = 15/treatment). Body weight (BW) was recorded on d -45, -26, 0, 8, 15, and 29. On d 0, an additional BW was taken 30 minutes after the 5-hour transportation (d 0.5). Between d 0 to 29, dry matter intake (DMI) and average daily gain (ADG) to DMI ratio (G:F) were measured. Between d -26 to 29 plasma concentrations of glucose, free fatty acids (NEFA), cortisol, insulin, total antioxidant status (TAS), and thiobarbituric acid-reactive substances (TBARS) were evaluated. Data were analyzed using the MIXED procedure of SAS with repeated measures, using treatment, time, and treatment × time as fixed effects, and steer as a random effect. Between d -26 to 0, there was an interaction of MVS × PC (P ˂ 0.01) for ADG. From d -26 to 0, N+N and N+PC had the greatest and lesser ADG, respectively. On d 0.5, no-PC steers tended to lose BW while the PC steers tended to gain BW (P = 0.09). In the period d 0 to 8, there were no differences (P ≥ 0.27) in DMI, but the PC steers had greater G:F and ADG (P < 0.01) compared with no-PC steers. Plasma NEFA concentration on d 0 was affected by MVS×PC (P < 0.01), because MVS decreased plasma NEFA concentration in no-PC steers, but it increased in the PC steers. Plasma concentrations of glucose, insulin, and cortisol did not differ among treatments (P ≥ 0.23). There was a MVS×PC interaction (P = 0.09) for TAS on d 0; N+N had the greatest and MVS+N had the lowest TAS concentrations. In conclusion, a 26-d PC decreased steers BW compared with no-PC steers. The BW loss during preconditioning was not recovered 29-d after feedlot entry. Despite this BW loss, MVS treatment decreased BW loss in the steers allocated to PC treatment on the day of transport.