Pain mitigation after band castration of beef calves and its effects on performance, behavior, Escherichia coli, and salivary cortisol1

Abstract

Eighty-nine steer and bull calves (210 +/- 20 d of age) were randomly assigned to a 2 x 2 factorial arrangement of treatments to study the effect of sham or band castration (CAST) with or without pain medication (MED) on performance, behavior, cortisol, and Escherichia coli shedding. Steers (serving as controls; C) were previously castrated at 34 +/- 10 d of age, whereas bulls (B) remained intact until band application on d 20 of the experiment. One-half of the calves in each group received pain medication (M; xylazine epidural and intravenous flunixin meglumine) or saline (NM) solutions at 0.5 h before castration. Feed intake, ADG, and feeding behavior were measured over a 3-wk period before (used as covariates) and a 6-wk period after castration. Fecal and saliva samples were collected from 32 calves for E. coli enumeration at -7 (covariate), 2, 5, and 7 d, and for cortisol concentration at -0.5 (covariate), 0, 0.5, 1, 2, 4, 24, 48, 168, and 336 h relative to castration, respectively. Lying behavior was measured in the home pen and step length at exit from the chute. There were no significant CAST x MED interactions on growth rate or feed intake. Overall ADG was less in B compared with C (P < 0.001), but feed intake was less during wk 4 only (P = 0.01). On average, M had less intake (P = 0.02) and eating rate (P = 0.04) than NM calves. The BM had less fecal E. coli counts than CM (P = 0.05) and castrated and nonmedicated calves (P = 0.08). Salivary cortisol was less in BM compared with the rest of treatments at 1 and 2 h after banding (P <or= 0.05). Castration reduced time spent lying (P = 0.06) and step length (P = 0.01) until d 28 after banding, whereas M reduced lying and step length on day of banding only (P <or= 0.06). Significant CAST x MED interactions were observed for frequency of visits to feeders and meal size, length, and frequency (P < 0.05) independent of the time after castration. This was due to greater values in the noncastrated and non-pain-medicated group compared with the rest, except for reduced meal frequency, indicating that pain medication and castration both affected feeding behavior. The medication protocol used in the present study eliminated the acute cortisol surge, which may be linked to reduced fecal E. coli counts observed during wk 1 after banding. However, feed intake, growth, and behavior suggested that pain was greatest during wk 3 and 4 after band application, which highlights the need for chronic pain mitigation strategies.