A COMPARISON OF STRESS IN SURGICALLY AND NONSURGICALLY MULESED SHEEP

A comparison has been made in 9- to 10-month-old castrated male Merino sheep of the changes in plasma total cortisol concentration and behav iour after being treated by either the modified Mules operation or by topical application of a quaternary ammonium compound to achieve non-s urgical mulesing. After surgical mulesing, plasma total cortisol conce ntration increased immediately and rapidly and reached a peak value in 15 minutes, whereas after non-surgical treatment an immediate rise di d not occur, but a similar peak value was observed in blood samples co llected 24 hours after treatment. The concentrations were lower in bot h groups at 48 hours. Likewise postural changes indicative of discomfo rt were immediately apparent in the surgically treated sheep, but not until 3 to 4 hours later in those treated non-surgically. Arena testin g revealed that a lasting aversion to the person who restrained them d uring treatment developed in the surgically mulesed sheep, but not in those treated non-surgically. The non-surgical procedure did not creat e large open wounds, as did the surgical operation, but still achieved similar enlargement of the bare area on the breech, and healing was q uicker in the non-surgically treated sheep.