The aim of this study by Marchant-Forde and colleagues at Purdue University was to evaluate stress responses evoked by two alternative methods for performing the following processing procedures:

1. teeth re-section (TR) - clipping versus grinding
2. tail-docking (TD) - cold versus hot-clipping
3. identification (ID) - ear notching versus tagging
4. iron administration (FE) - injection versus oral
5. castration (CA) - cords cut versus torn.

Experiment

Eight to 10 litters of eight, 2- and 3-day-old piglets were assigned to each procedure. Within each litter, 2 piglets were assigned to 1 of 4 possible procedures: the 2 alternative methods, a sham procedure, and a sham procedure plus blood sampling.

Blood was sampled before processing and at 45 min, 4 hours, 48 hours, 1 week and 2 weeks post-procedure and assayed for cortisol and beta-endorphin.

Procedures were video-taped and analyzed to evaluate the time taken to perform the procedure and the number of squeals, grunts and escape attempts. Vocalizations were analyzed to determine mean and peak frequencies and duration.

Piglets were weighed before the procedure and at 24 hours, 48 hours, 1 week and 2 weeks afterwards.

Lesions were scored on a 0 to 5 scale on ID, TD and CA pigs at 24 hours, 1 week, and 2 weeks post-procedure.

Results

For TR, grinding took longer than clipping and resulted in greater cortisol concentration overall, poorer growth rates and longer vocalizations compared to control treatment pigs (P<0.05).

For TD, hot clipping took longer and hot-clipped piglets grew slower than cold-clipped piglets (P<0.05). Hot clipping also resulted in longer and higher frequency squealing than control pigs (P<0.01).

For ID, ear notching took longer than tagging and ear-notched piglets had worse wound scores than tagged piglets (P<0.05). Cortisol concentrations at 4 hours also tended to be greater for notched piglets (P<0.10). Ear notching evoked calls with higher peak frequency than control treatments.

For FE, oral delivery took numerically longer than injecting, but there were no significant differences between injecting and oral delivery in any of the measures.

For CA, tearing took longer than cutting the cords (P < 0.05) but beta-endorphin concentrations at 45 min post-procedure were greater for cut piglets.

Using measures of behaviour, physiology and productivity, the responses to TR, TD and ID can be shown to be altered by method of procedure whereas responses to FE and CA did not differ.

The time taken to carry out the procedure would appear to be an important factor in the strength of the stress response.

Reference:
Marchant-Forde J.N., Lay D.C. Jr, McMunn K.A., Cheng H.W., Pajor E.A. and Marchant-Forde R.M. 2008. J. Anim. Sci., 2008 Nov 7. [Epub ahead of print]