Effects of early human handling on the pain sensitivity of young lambs

Abstract

Objective: Pain sensitivity of lambs changes over the first weeks of life. However, the effects of early treatments such as human handling on pain sensitivity are unknown for this species. This study investigated the effects of regular early gentle human handling on the pain sensitivity of lambs, indicated by their behavioural responses to tail docking.

Study design: Prospective part-blinded experimental study.

Animals: Twenty-nine singleton Coopworth lambs (females n=14, males n=15).

Methods: Starting at one day of age, lambs were either handled twice daily for 2 weeks (Handled), were kept in the presence of lambs who were being handled but were not handled themselves (Presence), or were exposed to a human only during routine feeding and care (Control). At 3 weeks of age, all lambs were tail docked using rubber rings. Changes in behaviour due to docking were calculated and change data were analyzed using two-way anova with treatment and test pen as main factors.

Results: All lambs showed significant increases in the frequency and duration of behaviours indicative of pain, including 'abnormal' behaviours, and decreases in the frequency and duration of 'normal' behaviours after docking. Handled lambs showed a smaller increase in the time spent lying abnormally after docking than did Control lambs (mean transformed change in proportion of 30 minutes spent±SE: Control 0.55±0.04; Handled 0.38±0.03; Presence 0.48±0.03; C versus H t=3.45, p=0.007).

Conclusions and clinical relevance: These results provide some evidence that handling early in life may reduce subsequent pain sensitivity in lambs. While the behavioural effects of handling on pain behaviour were subtle, the results suggest, at the very least, that early handling does not increase pain sensitivity in lambs and suggests there is still flexibility postnatally in the pain processing system of a precocial species.