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The objective of this study was to investigate the mechanisms of this disorder by conducting a comprehensive evaluation of gut health and function during early and chronic stages of PFTS. This study was conducted with pigs from a farm experiencing PFTS as previously described. Six treatment groups (n = 6 pigs/group) were designed as follows: 1) weaning baseline (CNT 0); 2) clinically unaffected pigs at day 4 post-weaning (CNT 4); 3) PFTS-affected pigs (early signs) at day 4 post-weaning (PFTS 4); 4) fasted pigs for 4 days (FAST); 5) clinically unaffected pigs at day 11 post-weaning (CNT 11); 6) PFTS-affected pigs (chronic signs) at day 11 post-weaning (PFTS 11). The FAST treatment pigs were used as a control to determine if changes in intestinal function were due to anorexia alone. At each time point described above, pigs were euthanized and samples of ileum were harvested for assessment of intestinal function and morphology. Intestinal function assays included measures of intestinal barrier function; transepithelial electrical resistance (TER) and mucosal to serosal FITC-dextran flux (m-sFD flux) on intestinal tissues mounted on Ussing chambers. Intestinal morphology was assessed in terms villus height and crypt depth.
Intestinal barrier function (intestinal permeability) was severely compromised in PFTS pigs, compared with unaffected controls, as demonstrated by decreased (P < 0.05) TER and increased (P < 0.01) m-sFD flux at day 4 and d11 PW in jejunal and ileal tissues. At d4 PW, fasted pigs also displayed impairment in intestinal barrier function compared with controls (P < 0.05) but the degree of barrier dysfunction was significantly less compared to that of PFTS affected pigs. Histopathologic analysis revealed villous atrophy and mucosal inflammation in both PFTSaffected and fasted pigs compared with controls. This was confirmed by villus height and calculated mucosal surface area analysis which showed reduced villus height (P < 0.05) and reduced surface area (P < 0.05) in PFTS and FAST pigs compared with CNT pigs at both 4 and 11 day post-weaning time points. The intestinal epithelial cells lining the majority of villi in PFTS pigs had an immature cuboidal appearance with diminished brush-border that was distinct from CNT and FAST pigs which had a normal columnar appearance.
This study demonstrates that PFTS is characterized by profound defects in intestinal mucosal barrier function at early and chronic stages of PFTS and distinct morphologic defects in intestinal epithelial cells. Furthermore, these data show that intestinal pathophysiology of PFTS does not appear to be solely attributed to anorexia as indices of mucosal barrier injury and altered epithelial morphology were significantly greater in PFTS pigs compared with FAST pigs.
A. Moeser, J. Pittman. Porcine peri-weaning failure to thrive syndrome (PFTS), Part III: Intestinal function and morphology. 2011 AASV Annual Meeting: 59
