Plasma concentrations of substance P and cortisol in beef calves after castration or simulated castration

Objective-To evaluate plasma concentrations of substance P (SP) and cortisol in calves after castration or simulated castration. Animals-10 Angus-crossbred calves. Procedures-Calves were acclimated for 5 days, assigned to a block on the basis of scrotal circumference, and randomly assigned to a castrated or simulated-castrated (control) group. Blood samples were collected twice before, at the time of (0 hours), and at several times points after castration or simulated castration. Vocalization and attitude scores were determined at time of castration or simulated castration. Plasma concentrations of SP and cortisol were determined by use of competitive and chemiluminescent enzyme immunoassays, respectively. Data were analyzed by use of repeated-measures analysis with a mixed model. Results-Mean +/- SEM cortisol concentration in castrated calves (78.88 +/- 10.07 nmol/L) was similar to that in uncastrated control calves (73.01 +/- 10.07 nmol/L). However, mean SP concentration in castrated calves (506.43 +/- 38.11 pg/mL) was significantly higher than the concentration in control calves (386.42 +/- 40.09 pg/mL). Mean cortisol concentration in calves with vocalization scores of 0 was not significantly different from the concentration in calves with vocalization scores of 3. However, calves with vocalization scores of 3 had significantly higher SP concentrations, compared with SP concentrations for calves with vocalization scores of 0. Conclusions and Clinical Relevance-Similar cortisol concentrations were measured in castrated and control calves. A significant increase in plasma concentrations of SP after castration suggested a likely association with nociception. These results may affect assessment of animal well-being in livestock production systems.