Cortisol responses to dehorning of calves given a 5-h local anaesthetic regimen plus phenylbutazone, ketoprofen, or adrenocorticotropic hormone prior to dehorning.

The purpose of this work was to assess whether the non-steroidal anti-inflammatory drugs (NSAIDs) phenylbutazone and ketoprofen, and an adrenocorticotropic hormone (ACTH) induced cortisol surge, reduce the cortisol response which occurs when the local anaesthetic wears off in calves following dehorning. There were four control groups and one dehorned group; also four groups were given local anaesthetic lasting 5h and were dehorned without or with phenylbutazone, ketoprofen or an ACTH injection, one group was injected with ACTH twice (at 0 and 6h) and another received ACTH and 6h later was dehorned. Blood samples were taken before and after dehorning and plasma cortisol concentrations were determined by radio-immunoassay. Dehorning increased the mean plasma cortisol concentrations [max 137 (11)nmoll(-1)] above control values [38 (5)nmoll(-1)] for about 7h, whereas local anaesthesia maintained concentrations at control values until about 5h after dehorning, and then they became elevated until about 10h. The maximum rise in mean concentration which occurred when the local anaesthetic wore off [128 (32)nmoll(-1)] was not affected when phenylbutazone was given before dehorning [141 (28)nmoll(-1)], but was reduced significantly when ketoprofen [65 (17)nmoll(-1)] or ACTH [61 (19)nmoll(-1)] were injected before or at the time of dehorning, respectively. Marked cortisol responses to ACTH injected at 0 and 6h were similar, but the early part of the cortisol response to dehorning 6h after an ACTH injection was reduced. It is suggested that the delayed cortisol response, which began 5h after dehorning, arose both from ketoprofen-sensitive and cortisol-sensitive sensory input as well as from other factors. Phenylbutazone did not affect the sensory input from the amputation wounds in the present calves.