303 - Effects of Supplementing Plexomin Zn™ on Post-transit Growth Performance and Plasma Zn and Serum Lactate Concentrations of Beef Steers

To determine effects of supplemental Zn on post-transit growth and plasma Zn and serum lactate concentrations, 54 Angus-cross steers (297 kg ± 12) were stratified by body weight to nine GrowSafe-equipped pens. Treatments began 25 d prior to transit and included: control (CON; no supplemental Zn), industry (IND; 70 mg supplemental Zn/kg DM), and supranutritional Zn (SUPZN; 120 mg supplemental Zn/kg DM). Supplemental Zn was provided as bis-glycinate bound Zn (Plexomin Zn; Phytobiotics North America, Cary, NC). On d 0, steers were loaded into a commercial trailer and transported 18 h (1,822 km). Individual BW were recorded on d -26, -25, -1, 0 (pre-transit), 1 (post-transit), 6, 27, and 28. Blood was collected on d -1, 1, 6, and 28. Data were analyzed using Proc Mixed of SAS with fixed effect of diet and steer as the experimental unit (n = 18 steers per treatment). Blood measures were analyzed as repeated measures with the repeated effect of day. Percent of pre-transit dry matter intake (DMI) was calculated relative to DMI for the 5 days prior to transit. Plasma Zn concentrations were greater in IND and SUPZN than CON (P = 0.01) and were greater on d 1 than d -1, 6, and 27 (P < 0.01). By d 2, both IND and SUPZN returned to pre-transit DMI levels while CON did not (P = 0.01). Further, DMI from d 1 to 28 was greatest in IND, intermediate in SUPZN, and least in CON (P = 0.04). Average daily gain from d 6 to 28 linearly improved with increasing Zn supplementation (P = 0.02). Regardless of treatment, serum lactate concentrations were greater post-transit compared to pre-transit values (P = 0.02). Steers supplemented dietary Zn recovered DMI faster and had greater ADG after a transit event.