Effects of sub-clinical post-weaning colibacillosis and dietary protein on acute phase proteins in weaner pigs

There is an increasing body of evidence that plasma acute phase proteins (APP) can be used as a marker to assess pig health. The objective of this study was to assess whether experimentally induced sub-clinical post-weaning colibacillosis (PWC) affects the concentration of two plasma APP, i.e. haptoglobin (Hp) and C-reactive protein (CRP). Since sub-clinical PWC is sensitive to protein supply, we additionally assessed whether these APP responses are sensitive to dietary protein contents. Weaned pigs (6 groups of 9 each) were offered one of the three foods, i.e. H (230 g CP/kg), L (130 g CP/kg) or HA (23% CP with anti-microbial growth promoters). On day 5 post-weaning, pigs were either dosed with 10(8) colony forming units of enterotoxigenic E. coli or were sham-infected. Three days later and across feeding treatments, infection had reduced feed intake. Feeding and infection treatment significantly interacted for both Hp and CRP. Infection increased Hp concentration in H and HA pigs, but not in L pigs, whilst infection increased CRP concentration to a larger extent in HA pigs than in H and L pigs. The results suggest that subclinical PWC leads to changes in APP profiles and that these changes may be sensitive to dietary protein contents. Usefulness of APP to describe health status in pigs may therefore need to be considered in relation to their nutritional environment.