Vocalisations by piglets
during castration: Punishing pain or purely protest?
L.A. Braithwaite, D.M. Weary
and D.G. Fraser
Agriculture and Agri-food
Canada, Ottawa, Canada
During the 19th C, the use of anaesthetic was predicated on the belief that sensitivity to pain varied according to the social status of the sufferer. At the bottom of the hierarchy, along with the lower classes, was the place of animals (Phillips, 1993). The use of anaesthetic is now habitual for veterinary animal surgery. However, there is growing concern about invasive procedures, such as piglet castration, that take place on farms without the benefit of anaesthetic. Piglets can be extremely vocal when handled and a commonly-held belief contends that since handling alone elicits so much calling, the actual castration can't be much worse. The aim of this experiment was to use vocalisations produced by piglets to distinguish between the distress caused by the handling necessary to perform a castration and the castration itself. Male piglets (n=26) were obtained from 13 litters (2 pigs/litter) and taken to a visually and acoustically isolated room. Treatments consisted of castration (C) and sham-castration (S-C). The C treatment was divided into 6 stages: "Restraint", "Alcohol", "Incision 1", "Incision 2", "Cut spermatic cords", and "Disinfectant". The S-C treatment also had 6 stages but during the "Incision 1&2" the scalpel was inverted and the dull edge of the blade traced down the scrotum and during the "Cut cords" the piglet was restrained for an equivalent amount of time. No significant differences were found between the 2 groups during the first 3 stages of the treatments. Rate of vocalisation (calls/s) was significantly greater in C vs S-C piglets during "Incision 2" (0.9+0.2 vs 0.5+0.1), "Cut spermatic cords" (1.1+0.1 vs 0.7+0.2) and "Disinfectant" (0.5+0.1 vs 0.3+0.07). During the "Cut cords" stage C piglets produced calls of significantly higher frequency (4483+209 vs 3482+412 Hz), longer duration (650+53 vs 446+65 ms) and larger amplitude (8 dB greater) than S-C piglets. In conclusion, castrated piglets produced more calls during the last 3 stages of castration and they produced louder, longer and higher frequency calls when the spermatic cords were cut. These results suggest that while the handling during castration is stressful, the actual castration procedure and particularly the cutting of the spermatic cords is significantly more distressing.
References
Phillips, M.T., 1993.
Savages, drunks and lab animals: The researcher's perception of pain. Society
and Animals, 1 (1): 61-81.