Effects of local anaesthesia of 4 to 8 hours' duration on the acute cortisol response to scoop dehorning in calves.
OBJECTIVE
To determine the effect of a long-acting local anaesthetic on the plasma cortisol response in calves dehorned using a scoop.


METHODS
A physiological study with controls.


METHODS
Seventy female calves, 3 to 4 months old, were divided into seven groups and dehorned by scoop with or without a long acting local anaesthetic (bupivacaine) which provides local anaesthesia for 3 to 4 h. In some treatment groups the local anaesthetic was given a second time, after 4 h, to give 8 h of anaesthesia. Blood samples were taken before and for 9 h after treatment and plasma cortisol concentrations were measured.


RESULTS
Scoop dehorning caused a marked rise in plasma cortisol concentration, which returned to pre-dehorning values after 7 h. The cortisol concentrations of calves given bupivacaine were similar to those of control animals for 4 h after dehorning, but then a significant and protracted rise occurred, with concentrations returning to pretreatment values at about 9 h after dehorning. In calves given a second treatment of bupivacaine 4 h after dehorning, the plasma cortisol concentration remained similar to control values for 8 h after dehorning but then increased sharply.


CONCLUSIONS
During its period of activity long-acting local anaesthetic prevented the rise usually seen after scoop dehorning in plasma cortisol concentrations; by inference it also alleviated the pain-induced distress caused by this procedure. However, when its effects had worn off the plasma cortisol values rose sharply indicating that animals still experienced pain-induced distress despite local anaesthetic being administered.
McMeekan
C M
CM
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Mellor
D J
DJ
Stafford
K J
KJ
Bruce
R A
RA
Ward
R N
RN
Gregory
N G
NG
D000772:Anesthesia, Local / Q000662:veterinary*; D000779:Anesthetics, Local; D000818:Animals; D002045:Bupivacaine; D002417:Cattle / Q000097:blood / Q000601:surgery*; D005260:Female; D006733:Horns / Q000601:surgery*; D006854:Hydrocortisone / Q000097:blood*; D013997:Time Factors
D000779:Anesthetics, Local; D006854:Hydrocortisone; D002045:Bupivacaine