Transportation stress increases serum concentrations of oxidative stress biomarkers that are related to episodes of BRD and mortality in calves.

No abstract

Forty-five Angus steers (avg initial wt 330 kg) were individually fed for 112 d to assess the value of supplemental Zn and source on performance and carcass quality. Steers had ad libitum access to a control diet (81 ppm Zn) of 33% whole corn, 33% ground milo, 15% cottonseed hulls and 13% cottonseed meal, or this control diet with 360 mg Zn/d added from either zinc methionine or zinc oxide. Steers were slaughtered on d 114, and carcass composition was determined by specific gravity. Average daily gain and feed efficiency were not affected by dietary treatments. Steers fed zinc methionine had a higher (P less than .05) USDA quality grade than those fed the control and zinc oxide diets. Marbling score was higher (P less than .05) for steers fed zinc methionine than for those fed control and zinc oxide treatments (4.4 vs 4.0 and 4.0, respectively, where 3 = slight, 4 = small, 5 = modest). Steers fed zinc methionine tended to have more (P less than .10) external fat (13 mm) than steers fed the control diet (10 mm); steers supplemented with zinc oxide had intermediate amounts of external fat (11 mm). Steers fed zinc methionine had 10.5 and 12.8% more (P less than .05) kidney, pelvic and heart (KPH) fat than steers fed control or zinc oxide diets, respectively. The effects of zinc methionine on carcass quality grade and marbling score may be due to Zn and (or) methionine. Regardless of the mechanism, the difference represents a potential economic benefit to producers.

Three experiments were conducted using feedlot steers in a randomized block design to determine the effect of zinc methionine (ZnMet) and zinc oxide (Exp. 3) on feed intake (DMI), rectal temperature, and serum mineral concentrations of feedlot cattle challenged with infectious bovine rhinotracheitis virus (IBRV). All the steers used were seronegative to IBRV. Steers were adapted for 7 d to their respective diets and challenged with 3.7 x 10(5) plaque forming units of IRBV on d 0 of each experiment. Live BW, rectal temperature, and individual daily DMI were recorded for 14 d. Blood samples were taken on d 0, 7, and 14. In Exp. 1, daily DMI of the control steers (Zn = 31 ppm) decreased 50% compared with 15% in the ZnMet (Zn = 90 ppm) steers 3 d after IBRV challenge. By d 6, the ZnMet steers had regained their pretrial mean daily DMI, but the control steers took 11 d. The ZnMet steers had lower (P less than .05) mean rectal temperature than the control steers on d 7 and 12. In Exp. 2, the control (Zn = 35 ppm) steers had lower (P less than .05) daily DMI on d 8 to 12 than the ZnMet (Zn = 89 ppm) steers. In Exp. 3, the mean decrease in daily DMI tended to be more rapid in the ZnO steers than in the control and ZnMet steers. All steers had the lowest daily DMI on d 5 and 6, coinciding with the highest rectal temperature. Serum Zn, P, and Mg concentrations decreased and serum Cu increased in all steers after infection. These data suggest that dietary Zn enhanced the recovery rate of IBRV-stressed cattle.