PLASMA-CORTISOL AND WHITE BLOOD-CELL RESPONSES IN DIFFERENT BREEDS OFBULLS - A COMPARISON OF 2 METHODS OF CASTRATION

To determine plasma cortisol and white blood cell response to castrati on, Angus (n = 12, 21.4 mo of age), Hereford (n = 6, 21.2 mo of age), and Brahman (n = 24, 20.3 mo of age) bulls nearing maturity were eithe r left intact as uncastrated controls (CON), surgically castrated (SUR ) after lidocaine, or castrated by latex rubber banding (BAN). Before and through 35 d after castration (castration = d 0), animals were wei ghed and blood samples were collected for analysis of cortisol and tot al white blood cell (WBC) count at 2-, 3-, or 7-d intervals. There was a treatment x breed interaction for ADG from d 0 to 7 (P < .05). From d 0 to 14, 0 to 21, 0 to 28, and 0 to 35, ADG tended to be lower for SUR and BAN animals than for CON animals (castrated vs CON, P less tha n or equal to .13). No significant differences in ADG were observed be tween SUR and BAN animals during these times. On d 0, from just before treatment to just after treatment, plasma cortisol concentration incr eased 3.2 ng/mL for SUR and .1 ng/mL for BAN (SEM = +/- .5 ng/mL; SUR vs BAN, P < .03). From d 0 pretreatment to d 2 after treatment, plasma cortisol concentration increased 1.5 ng/mL for castrated (SUR = 2.0 a nd BAN = 1.1 ng/mL) and decreased 1.6 ng/mL for CON (SEM = +/- .7 ng/m L; P < .04). Plasma cortisol concentration was negatively correlated ( P < .001) with BW (r = -.17) and BW change (r = -.19). Two days after castration, WBC counts were higher (P < .01) in castrated (SUR = 10,81 2 and BAN = 11,498 cells/mu L) than in CON (8,629 cells/mu L) animals (SEM = +/- 278 cells/mu L). Breed affected ADG (P < .05) and WBC (P < .01) but did not affect plasma cortisol concentration. Castration of b ulls nearing maturity by both SUR and BAN procedures elicited short-te rm elevations in cortisol and WBC and reduced ADG compared with CON. T he only difference observed between SUR and BAN treatments was an elev ated plasma cortisol in SUR animals just after castration.