Abstract
Dairy calves are routinely disbudded by cauterization with a hot iron. To mitigate the intra-operative and initial post-operative pain associated with this procedure some farmers provide calves general and local anesthetics, but it is unknown if the procedure remains aversive. We used a place-conditioning paradigm to assess aversion caused by hot-iron cautery with a local anesthetic compared to a sham procedure. A test area was divided into three equally sized pens: two ‘treatment’ pens with distinct visual cues were connected by a central ‘neutral’ pen. Each calf went through the disbudding procedure and a 6-h recovery period in one treatment pen and the control procedure in the other treatment pen. In three tests (48, 72 and 96 h after the second treatment), calves could freely roam among the pens until they chose to lie down, ending the session. Calves spent less time in either of the treatment pens compared to the central pen. When only comparing the two treatment pen, calves spent less time in the disbudding pen, especially during the first test. Calves were also less likely to lie down in the pen associated with the disbudding procedure. We conclude that even with the use of a local anesthetic, hot-iron disbudding is salient and aversive for calves, indicating the need to refine or avoid the procedure.
Highlights
Horned cows can be a safety concern for pen mates and their handlers, so the developing horn buds of dairy calves are typically removed via hot-iron cauterization[1]
Rats will avoid an environment associated with the ingestion of an emetic agent[30] and zebrafish will avoid the side of a tank associated with anesthetic agents[31]
Calves spent less time in the treatment pens compared to the middle pen (Control pen: t2,67 = −3.3, P = 0.001; Disbudding pen: t2,67 = −5.4, P < 0.001; Fig. 2)
Summary
Horned cows can be a safety concern for pen mates and their handlers, so the developing horn buds of dairy calves are typically removed via hot-iron cauterization (known as “disbudding”, or “dehorning” when done at a later age)[1] This procedure is painful[2,3] and methods to reduce or prevent this pain have gathered considerable scientific interest[4,5,6]. Commonly used are “pain-related” behaviors such as ear flicks, head shakes, or head rubs[9,19,20] Such responses can be informative regarding the acute sensory-discriminative aspect of the procedure (i.e. nociception), but similar behaviors are sometimes expressed by anesthetized or decerebrate animals[21,22,23] suggesting some difficulty in drawing strong inferences regarding the affective-motivational component of the experience[24]. Place conditioning has not yet been applied to evaluate pain in cattle
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