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 s.c. injection of meloxicam (M) at the time of castration (0.5 mg Metacam®/kg BW) or single s.c. injection of saline solution as control (N). Calves were managed in two groups (GROUP) of 36 to be castrated on two separate days, two weeks apart. Calves were housed on pasture with ad libitum access to water. Temperament was assessed by measuring flight speed (FS, m·s^-1); faster animals indicated more excitable temperament. Growth performance was assessed using ADG (kg·d^-1). Substance P (SP, pg·mL^-1) 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, d -1 (prior to castration day) and d 0 (immediately prior to castration) as baseline measurements; and on d 6, 13, 20, 34, 48 and 62 post castration (DAY). Calves were blocked by the average FS and BW obtained on d -6 and d -1. Data was analyzed using a mixed-effects model including CAST, DRUG, DAY and its interactions as fixed effects, and GROUP as 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 d 0 were used as covariates. Growth performance was greater (P < 0.05) in S (1.33 ± 0.03 kg·d^-1) than K and B (1.21 ± 0.03 and 1.22 ± 0.03 kg.d^-1, respectively). For every 1 m·s^-1 increment in FS SP decreased by 8.7 pg·mL^-1 (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 to S. Faster FS was associated with lower pain levels indicating that temperament can affect physiological measures. A single s.c. injection of meloxicam had no effect on growth performance or the indicators of pain used in this study.