PERFORMANCE AND HEALTH OF WEANLING BULLS AFTER BUTORPHANOL AND XYLAZINE ADMINISTRATION AT CASTRATION

A total of 268 crossbred, 6- to 9-mo-old, bull calves [214 +/- 19 kg] were used in two separate 27-d experiments to assess the effects of butorphanol and xylazine administration [BXA] on the subsequent performance and health of beef calves. In each experiment, calves were randomly allotted to four treatment groups: 1] castration with BXA, 2] castration without BXA, 3] no castration with BXA, and 4] no castration without BXA. There were two replicates within each experiment. The intravenous administration of .07 mg/kg of butorphanol and .02 mg/kg of xylazine occurred 90 s before tail hold and castration procedures. Calves were placed in a squeeze chute and manually restrained by tail elevation. In Exp. 2, the cattle also were scored for chute activity [on a 1 to 5 scale with 5 being the most active]. Cattle were weighed at the beginning and end of the experiment, feed intake was recorded daily, and cattle were monitored daily for respiratory disease. There were no castration x BXA interactions [P > .51]. Castration reduced [P < .01] daily gain and gain/feed and tended [P = .13] to reduce feed intake. The administration of BXA had no effect [P > .05] on gain or gain/feed but did tend [P = .13] to reduce feed intake. No differences [P > .45] were observed in morbidity or mortality due to either BXA or castration. Castration and BXA increased [P < .01] blood cortisol levels on d 3, whereas control animals had reduced cortisol levels. Castration increased [P < .05] haptoglobin levels on d 3, but BXA had no effect [P > .05] on serum haptoglobin concentrations on d 3. Chute activity was reduced [P < .05] by castration and BXA. In this study, animal performance was reduced by castration. The administration of BXA did not alter stress indicators or improve performance of castrated bull calves. Serum haptoglobin may be a more specific indicator of the inflammatory process in cattle, whereas serum cortisol may be an indicator of the whole-body stress response.