The influence of handling by humans on the behaviour,reproduction and corticosteroids of male and female pigs

The influence of three handling treatments on the behaviour, reproduction and free corticosteroid concentrations was studied in 15 male and 30 female pigs. Two handling treatments, considered as pleasant and unpleasant, were imposed for 5 min, three times per week from 11 weeks of age. The third handling treatment involved minimal contact with humans from 11 weeks of age. In a 3-min test at 18 weeks, pigs in the pleasant treatment were quicker (P<0.01) to enter an area within 0.5 m of the experimenter and had more interactions (P<0.05) with the experimenter than pigs in the unpleasant and minimal treatments. Gilts in the unpleasant treatment had a lower (P<0.05) pregnancy rate at the second oestrus when mated to non-experimental boars than gilts in the pleasant treatment (33.3 and 87.5%, respectively). Boars in the unpleasant treatment had smaller (P<0.05) testicles at 23 weeks of age and attained a coordinated mating response at a later age (P<0.05) than boars in the pleasant treatment (53.2 and 63.3 cm², and 192 and 161 days, respectively). In addition, pigs in the unpleasant treatment had higher (P<0.05) free corticosteroid concentrations in the absence of humans at 20 weeks (gilts) and 27 weeks (boars) than pigs in the pleasant treatment (boars and gilts combined, 2.4 and 1.7 ng ml⁻¹, respectively). For many of the reproductive parameters, the effect of the minimal handling treatment was intermediate to that of the other two treatments. It was concluded that the unpleasant handling treatment resulted in a chronic stress response, with consequent adverse effects on reproduction.