Issues and possible intervention strategies relating to early weaning of piglets.

Abstract

Abstract Early weaning of farmed pigs before 25 days of age is a complex multi-factor stressor, often leading to health and welfare issues. The most obvious and crucial feature is that many piglets do not consume food in this period. On this basis, the final stressing impact is derived from a combination of physical, nutritional, immunological and emotional components. On the whole, there is strong evidence that a reduction in the pigs' weaning age can lead to increased adaptation difficulties in terms of behavioural, neuroendocrine and immune responses, as also observed by means of clinical immunology and chemistry analyses. This is the argument underlying the recommended minimum age of 28 days at weaning in EU Directive 2001/93/EC. Inflammatory, stress and innate immune responses sustain the coping efforts of piglets at weaning. Some responses are weaning-specific, whereas others reflect the related social stress of regrouping (mixing) and separation from the sow. An innate immune response to tissue damage at weaning (shorter, atrophic villi and larger, deeper crypts) and relevant control mechanisms are likely to be of paramount importance. In this respect, type I (α/β) interferons (IFNs) were shown to play a major regulatory role of the inflammatory response at weaning. Also, a low-dose, oral IFN-α treatment was shown to sustain the coping efforts of piglets. These results are of some importance in view of a global assessment of food safety 'from farm to fork', and of the related need to reduce the extensive, diarrhoea-related use of drug-supplemented feeds after weaning.