Maintaining the barrier function of the intestine is tantamount to maintaining the health and productivity of pigs at weaning.

Properly functioning intestinal tissue acts as a selective barrier to allow nutrients in and to keep pathogens and antigens out. Loss of this barrier function increases the pigs’ susceptibility to intestinal infections and increases the energy utilized to mount an immune response. Stress reduces the barrier function of the intestine; however, the mechanism by which this occurs is unclear.

The role of stress-induced loss of barrier function is of particular importance to newly weaned pigs, because the weaning process causes both physical and psychological stress. Additionally, intestinal disturbances that occur while the intestine is still developing may have even longer lasting consequences.

Recent work conducted at the College of Veterinary Medicine by Dr Adam Moeser and his collaborators examined the impact of weaning age on intestinal barrier function. A clear effect of increasing weaning age decreasing intestinal permeability was seen in this study (Figure 1).

What was most interesting about this impact of weaning age on intestinal permeability was that differences were still apparent over five weeks after weaning (Figure 2). This suggests that just a few days difference in weaning age can have effects on the intestinal health of pigs throughout the nursery.

Dr Moeser and his research group also identified a potential mechanism for the loss of barrier function that was seen with earlier weaning ages. They found that a type of immune cell (mast cell) was found in greater numbers in the intestinal epithelium of early weaned pigs and that signalling of corticotrophin-releasing factor through these mast cells may result in the loss of barrier function.

By elucidating the mechanism by which stress-induced loss of intestinal barrier function occurs, Dr Moeser hopes to identify novel methods to ameliorate this condition. For now, it is clear that increased weaning age has potential for improving lifetime intestinal health.

This research is reported in its entirety as ‘Early weaning stress impairs development of mucosal barrier function in the porcine intestine’ Am. J. Physiol. Gastrointest. Liver Physiol., 298: G352–G363, 2010.