The fighting behaviour of piglets mixed before and after weaning in the presence or absence of a sow

Abrupt weaning of piglets is a stressful event that is often associated with vigorous fighting, a growth check and digestive disorders. Allowing piglets to co-mingle approximately 2 weeks before weaning has been shown to reduce fighting in the post-weaning period although pre-weaning growth rates may be adversely affected due to disrupted suckling behaviour. This study tested the hypothesis that allowing piglets to co-mingle at only 5 days pre-weaning would still reduce fighting in the post-weaning period but would minimise the adverse effects on pre-weaning growth rates. Experiments were conducted on a commercial pig farm in south-west England. Boards were removed from the backs of three adjacent farrowing crates, thereby allowing piglets access to a communal corridor and to the three crates; the piglets in control litters were not allowed to co-mingle. Weight gain and skin lesions were monitored and fighting behaviour was recorded using video cameras. Allowing piglets to co-mingle at 5 days pre-weaning did not affect growth rates in either the pre-weaning or post-weaning periods and mixed piglets showed significantly reduced fighting in the immediate post-weaning period than controls. However, mixed piglets showed significantly increased fighting in the pre-weaning period. The fighting was confined to the communal corridor and did not occur in the areas around the sows, despite the fact that piglets were cross-suckling and were exploring creep box areas other than their own. The results of this study show that pre-weaning mixing can be used to reduce fighting in the post-weaning period and may, at first sight, appear to be a useful technique to reduce post-weaning stressors. However, before such a practice can be fully endorsed, it is important to investigate the full consequences, as simply moving the mixing stressor to the pre-weaning period may actually have a detrimental effect on the welfare of piglets.