012 Meloxicam and temperament effects on growth performance and indicators of pain in knife or band castrated calves housed on pasture

The objective of this study was to evaluate the effect of castration method, meloxicam, and temperament on growth performance and indicators of pain in band- or knife-castrated beef calves. Seventy-two crossbred Angus calves (76 ± 2 d of age and 134.5 ± 20.30 kg BW) were randomly assigned to treatments according to a 3 × 2 factorial design assessing castration technique (CAST; knife [K], band [B], or sham castration [S]) and drug administration (DRUG; single subcutaneous injection of meloxicam at the time of castration [0.5 mg Metacam/kg BW] or single subcutaneous injection of saline solution as control). Calves were managed in 2 groups (GROUP) of 36 to be castrated on 2 separate days, 2 wk apart. Calves were housed on pasture with ad libitum access to water. Temperament was assessed by measuring flight speed (FS; m/s); faster animals indicated more excitable temperament. Growth performance was assessed using ADG (kg/d). Substance P (SP; pg/mL) and stride length (SL; cm) were used as physiological and behavioral indicators of pain, respectively; greater SP and SL values indicated greater and lower pain levels, respectively. Initial BW and FS were collected on d −6, −1 (prior to castration day), and 0 (immediately prior to castration) as baseline measurements and on d 6, 13, 20, 34, 48, and 62 after castration (DAY). Calves were blocked by the average FS and BW obtained on d −6 and −1. Data was analyzed using a mixed-effects model including CAST, DRUG, DAY, and their interactions as fixed effects and GROUP as a random effect. The average baseline measurements of BW, the average of all FS measurements, and the average of SP or SL obtained on d −1 and 0 were used as covariates. Growth performance was greater (P < 0.05) in S (1.33 ± 0.03 kg/d) than in K and B (1.21 ± 0.03 and 1.22 ± 0.03 kg/d, respectively). For every 1 m/s increment in FS, SP decreased by 8.7 pg/mL (P < 0.05). There was no effect of CAST, DRUG, or FS on SL. As expected, both knife- and band-castrated calves had reduced ADG compared with S calves. Faster FS was associated with lower pain levels, indicating that temperament can affect physiological measures. A single subcutaneous injection of meloxicam had no effect on growth performance or the indicators of pain used in this study