Effect of zinc and chromium supplementation on performance and carcass characteristics in feedlot steers

One hundred and sixty-five crossbred steers were used in this experiment to investigate the influence of supplemental zinc (Zn) and chromium (Cr) on performance and carcass characteristics of feedlot steers fed steam-flaked corn-based finishing diet. Steers were blocked by initial BW (518.9 ± 8.4 kg) within cattle source (2 sources) and housed in pens containing 6-7 steers per pen. Pens within blocks were randomly assigned to treatments in a 2 x 2 factorial arrangement, with factors being: 30 or 90 mg of Zn/kg DM and 0.0 or 0.25 mg Cr/kg DM. Treatments consisted of: 1) 30 mg Zn/kg DM; 2) 90 mg Zn/kg DM; 3) 30 mg Zn + 0.25 mg Cr/kg DM; and 4) 90 mg Zn/kg + 0.25 mg Cr/kg DM. Zinc was supplemented as ZnSO4 and Cr supplemented as Cr propionate. Steers were individually weighted on 2 consecutive days prior to initiating dietary treatment and on 2 consecutive days at the end of the experiment. Dietary treatment were initiated 64 days prior to slaughter (total days on feed = 240). All cattle were transported to a commercial abattoir on the same day and slaughtered. Steers receiving supplemental Cr had greater final BW (P < 0.02) and ADG (P < 0.03) when compared to non-Cr supplemented steers. Additionally, hot carcass weight (P < 0.005) and marbling score (P < 0.03) were greater (P < 0.005) for steers receiving 30 mg Zn/kg DM + 0.25 mg Cr/kg DM when compared with all other treatments. Dry matter intake, morbidity and mortality, and all the other carcass measurements were similar across treatments. These data indicate that under the conditions of this experiment, Zn and Cr supplementation may influence feedlot cattle growth and carcass characteristics.