Feed restriction as a model for small intestinal permeability in nursery pigs

Reduced feed intake is a hallmark of many animal diseases and environmental conditions and has been shown to cause intestinal barrier dysfunction. As there are several markers and assays to evaluate intestinal barrier function, feed restriction may present a potential model to validate and compare multiple in vivo, ex vivo, and tissue markers of intestinal integrity. Forty-eight barrows (9.7 kg initial body weight) were fed for 7 d at feed intakes of 100%, 75%, 50%, or 25% of expected ad libitum feed intake. After which urine, and blood were taken for in vivo lactulose:mannitol analysis. Additional ileum samples were taken for examination of intestinal function including ex vivo tissue transepithelial electrical resistance (TEER), tissue fluorescein isothiocyanate-dextran (FD4) transport, as well as small intestinal villus height and crypt depth, and gene expression. Data were analyzed as an ANOVA as well as a contrast where 25% and 50% were combined, as were 75% and 100%. As expected, observed feed intake followed a linear pattern, as did body weight changes. Pigs fed ad libitum (100%) gained 3.8 kg whereas pigs fed at 75% restriction gained 2.5 kg, pigs fed at 50% restriction gained 1.2 kg and pigs fed at 25% lost 0.37 kg (P < 0.05). Results showed tissue changes in morphology in duodenum, jejunum and ileum at 25% and 50% feed restriction (P < 0.05). Specifically, pigs fed at 75% and 100% feed levels had on average a 26% greater villus height compared to pigs fed at 50% and 25% (P < 0.01). There were no significant differences in TEER, however there was also a tendency for a contrast difference for FD4 as well as for a significant increase in urinary lactulose:mannitol at 25% compared to 75% and 100% (P < 0.10). Similarly, pro-inflammatory gene marker, IL17A was increased at 25% feeding level compared to 75% and 100% (P < 0.05). Taken together, these data show that feed restriction may be a good model to compare validation methods for intestinal permeability and function, but that length of feed restriction may have reduced larger impacts on intestinal function observed in other studies.