Papers of the Week

The objective of this study was to determine the effects of flunixin meglumine or meloxicam on behavioral response and performance characteristics associated with surgical castration in crossbred bulls. Intact male Bos taurus calves (n = 252; averaging 176 kg) were randomly allocated into one of three treatment groups within pen: control (CON), flunixin meglumine (FLU; 2.2 mg per kg intravenous injection), or meloxicam (MEL; 2.0 mg per kg per os). Individual animal was the experimental unit. Calves were individually weighed on day (d) 0 and 14 of the trial to evaluate performance outcomes. On study d 0, treatments were administered, according to their random allocation, immediately prior to surgical castration using the Henderson tool method. Visual analog scale (VAS) assessment and categorical attitude score (CAS) were collected on d -1, 0 (6 h post-castration), 1, 2, 3, and 4 in the study. The VAS was assigned using a 100 mm horizontal line with 'normal' labeled at one end of the line and 'moribund' at the other end of the horizontal line. The masked observer assigned a mark on the horizontal line based upon the observed severity of pain exhibited by that individual animal. The CAS was assigned by the same observer using 5 different categories with a score of 0 being "normal". Average daily gain tended (P = 0.09) to be associated with treatment group, and MEL had greater (P = 0.04) average daily gain through day 14 compared to CON. A significant (P < 0.01) treatment by day interaction was indicated for VAS score, and MEL had lower VAS scores on d 0, 1, 2, and 3 post-castration compared to CON; FLU had lower VAS scores on d 0 and 1 compared to CON. A significant treatment by day interaction was not present (P = 0.25) for CAS. The FLU had lesser percent CAS ≥ 1 (17.5%; P = 0.05) compared to CON (29.4%); MEL has lesser percent CAS ≥ 1 observations (14.9%; P = 0.01) compared to CON. The median VAS increased as CAS was more severe. Results indicated MEL and FLU calves temporally improved behavioral responses following surgical castration with positive numerical trends for a 14 d ADG. The VAS system appeared to be an effective method of subjective evaluation of pain in beef calves in this study. Route of administration, duration of therapy, and low relative cost make oral meloxicam a reasonable analgesic treatment in calves when administered at the time of surgical castration.