Dietary zinc and manganese sources administered from the fetal stage onwards affect immune response of transit stressed and virus infected offspring steer calves

Nutritional stress encountered during the marketing and transportation of calves often results in excessive loss of micronutrients including zinc and manganese. The role of dietary zinc (Zn) and manganese (Mn) sources in enhancing the total body immune response of steer calves stressed by transportation and challenged with infectious bovine rhinotracheitis virus (IBRV) was investigated in this study. Forty steer calves (average body weight (BW) = 232 kg) were used in an experiment to determine the effects of the type of Zn and Mn supplementation to dams (100 days pre-partum) and calves (pre- and post-transit), on calf performance, dry matter intake (DMI), rectal temperature (RT) and BW changes after transit and after IBRV challenge. Data were also analyzed for the period after transit and following IBRV challenge. From pregnancy to weaning, the dams and calves received the following mineral supplements: (1) zinc methionine+manganese methionine (ZnMnMet; Zn=50 mg/kg, Mn=40 mg/kg), or (2) ZnO+MnO (ZnMnO; Zn=50 mg/kg, Mn=40 mg/kg). Calves were weaned and shipped approximately 2500 km from Raleigh, NC, to Bushland, TX. At the feedlot, the calves received the same supplements in a complete diet for 28 days (stress phase), and subsequently were challenged with IBRV (IBRV phase). During the 28-day period after transit, steers fed the ZnMnMet had higher (P<0.05) DMI and gained (weight) faster (P<0.05) than those fed ZnMnO. During the IBRV challenge phase, steers fed ZnMnMet averaged 20.4% higher (P<0.05) DMI than the steers fed ZnMnO. These steers also exhibited lower (P<0.05) RT and retained higher (P<0.05) BW than those fed ZnMnO. These data indicate that a dietary organic Zn and Mn combination mitigated transit stress and IBRV infection of steer calves better than its inorganic counterpart.