Effects of suppressing cortisol following castration of bull calves on adrenocorticotropic hormone, in vitro interferon-gamma production, leukocytes, acute-phase proteins, growth, and feed intake

The objective was to determine the effects of reducing the plasma cortisol rise in calves following castration on plasma ACTH concentrations, keyhole limpet hemocyanin (KLH)- and concanavalin A (Con A)-induced in vitro interferon (IFN)-[Gamma] production, white blood cell (WBC) numbers, neutrophil:lymphocyte (N:L) ratio, plasma haptoglobin and fibrinogen concentrations, ADG, and ADFI. Forty 5-mo-old Friesian bull calves (169 [+ or -] 1.7 kg) were assigned to four treatments: 1) control (CON); 2) oral metyrapone administration (MET); 3) surgical castration at 0 h on d 0 (SURG); and 4) oral metyrapone administration and surgical castration (MET + SURG). Cortisol, ACTH, IFN-[Gamma] production, haptoglobin, fibrinogen, ADFI, and ADG were not different between CON and MET animals. The MET + SURG calves had lower (P < .001) peak and mean cortisol during .25 to 1.5 h than SURG animals, but area under the cortisol vs time curve from 0 to 12 h did not differ (P > .39) between SURG and MET + SURG calves. Peak ACTH concentrations and area under the ACTH vs time curve from 0 to 6 h were greater (P < .05) for MET + SURG than for SURG calves. There were no differences between MET + SURG and SURG animals in IFN-[Gamma] production, WBC numbers, and ADFI. On d 1, MET + SURG and SURG animals had lower (P Key Words: Cattle, Stress, Hydrocortisone, Castration, Metyrapone, Interferon