EFFECT OF CASTRATION METHOD AND THE PROVISION OF LOCAL-ANESTHESIA ON PLASMA-CORTISOL, SCROTAL CIRCUMFERENCE, GROWTH, AND FEED-INTAKE OF BULL CALVES

To determine the effects of castration of calves, with or without loca l anesthesia, on plasma cortisol, scrotal circumference, ADG, and ADFI , 56 Friesian bulls (5.5 mo of age; mean +/- SE BW = 173 +/- 2 kg) wer e randomly assigned to each of seven treatments: 1) control (CON); 2) s.c. injection of .1 mg of a human serum albumin-GnRH conjugate with D EAE-dextran adjuvant (HSA-GnRH); 3) burdizzo castration without local anesthetic (BURD); 4) burdizzo castration following local anesthetic a dministration (BURD + LA); 5) surgical castration without local anesth etic (SURG); 6) surgical castration following local anesthetic adminis tration (SURG + LA); and 7) local anesthetic administration alone (LAA ). Blood samples for cortisol analyses were taken via jugular catheter from -2 to 10 h and at 24, 48, and 72 h relative to treatment. Averag e daily feed intakes were recorded for 5-d periods and calves weighed at 7-d intervals before and after treatment. Local anesthetic alone ha d no effect (P > .10) on any variable. The HSA-GnRH calves had elevate d (P < .05) plasma cortisol from 2 to 6 h compared with CON calves. Pe ak plasma cortisol was elevated (P < .01) in BURD, BURD + LA, SURG, an d SURG + LA compared with CON calves. The SURG calves (46.0 ng/mL) had higher (P < .03) peak cortisol than BURD (31.4 ng/mL) and SURG + LA ( 35.4 ng/mL) calves. There was no difference in peak cortisol between B URD and BURD + LA (26.5 ng/mL) calves. The ADG from d 0 to 7 was reduc ed (P < .05) in calves in BURD + LA, SURG, and SURG + LA treatments (- .01, -.83 and -.24 kg, respectively) compared with CON calves (.54 kg) . The ADFI were reduced (P < .05) in BURD and BURD + LA calves during d 1 to 5 and in BURD + LA, SURG, and SURG + LA calves during d 6 to 10 compared with CON calves. The scrotal circumferences of BURD and BURD + LA calves were greater (P < .05) than those of CON calves for 7- an d 35-d periods post-castration, respectively. Castration induced incre ases in cortisol and decreases in ADG and ADFI. Surgical castration in duced a greater plasma cortisol response than burdizzo castration, and the administration of local anesthetic reduced the cortisol response of surgical castrates but was less effective for burdizzo castrates.