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ISU scientists pinpoint indicators of acute pain in neonatal pigs

Indicators of acute pain in piglets have been identified by researchers from Iowa State University (ISU).¹

Mounting consumer interest in livestock welfare was the impetus for the study, which was aimed at finding ways to measure pain associated with procedures commonly performed on young pigs, said ISU student Brent Sexton at the 2017 annual meeting of the American Association of Swine Veterinarians.

The researchers randomly allocated 58 gilts and 62 boars, age 3 to 6 days, to one of four groups:

1. Females that were not tail-docked
2. Males that were not tail-docked and castrated
3. Females that were tail-docked
4. Males that were tail-docked and castrated

Groups 1 and 2 served as controls. All pigs in the study received an iron injection.

Sexton and colleagues recorded behaviors before and after treatment. They took activity scans every 2 minutes for the first 20 minutes and then every 5 minutes for the remainder of 2 hours. They also took rectal temperatures immediately before treatment, immediately after treatment and 20 minutes after treatment.

Hunched posture, lethargy, stiff gait and trembling occurred more often in tail-docked, castrated males (Group 4) compared to the other groups. These behaviors may be better indicators of acute pain in neonatal piglets than others, he said.

The frequency and duration of nursing decreased in all groups after treatment, though not significantly.

In addition, there were no observable differences between groups regarding huddling, lying and isolation, indicating these behaviors are poor indicators of acute pain in piglets. There were also no significant differences in mean rectal temperatures before and after treatment, he said.

“Overall, these results identify specific behaviors that should be assessed in future comparisons of pain-mitigation strategies for processed piglets,” Sexton said.

[1] Sexton B, et al. Determination of behavioral and physiological pain indicators associated with castration and tail docking in young piglets.  In: Proceedings of the 48^th Annual Meeting of the American Association of Swine Veterinarians (February 25-28, 2017). Page 268.