222 Awardee Talk: What we Know Now: Strategic Zinc Supplementation for Cattle Utilizing Growth Promoting Technologies

Abstract

Abstract A 98-d study examined the effects of increasing supplemental Zn on cattle performance, plasma Zn concentrations, and nitrogen metabolism using 92 Angus-crossbred steers (424 ± 28 kg) administered growth-promoting technologies. Steers were implanted with Component TE-200 (Elanco, Greenfield, IN) on d 0 and fed 300 mg‧steer-1‧d-1 of ractopamine hydrochloride (Zoetis, Parsippany, NJ) from d 70-98. Pens were equipped with GrowSafe bunks (GrowSafe Systems Ltd., Airdrie, AB, Canada), and steer served as the experimental unit (n = 22 or 23 steers/treatment). Dietary Zn treatments included 0, 100, 150, and 180 mg Zn/kg dry matter from ZnSO4 (Zn0, Zn100, Zn150, and Zn180, respectively). Data were analyzed via the Mixed and Corr procedures of SAS. Contrast statements tested linear, quadratic, and cubic effects of Zn supplementation and Zn0 vs. Zn supplementation. Day 10 and 70 body weights and d 0-10 and 0-70 average daily gain were linearly increased with increasing Zn supplementation (P ≤ 0.05), and greater for Zn supplemented steers (P ≤ 0.03). Concurrently, d 10 and 69 plasma Zn concentrations linearly increased (P ≤ 0.03). Final body weight, dressing percentage, ribeye area, 12th rib fat, and marbling were not influenced by Zn supplementation (P ≥ 0.11). Hot carcass weight tended to be 7 kg greater for Zn supplemented steers than Zn0 (P = 0.07). Day 10 liver Mn tended to be positively correlated with d 10 liver arginase activity (r = 0.27; P = 0.07) and was positively correlated with d 10 serum urea nitrogen (r = 0.55; P < 0.0001). Neither d 79 liver arginase activity nor serum urea nitrogen were correlated with d 79 liver Mn (P ≥ 0.21). These data suggest increased supplemental Zn is beneficial to growth directly following implant administration and that implants and beta agonists differentially influence nitrogen metabolism.