Effects of low-molecular-weight chitosan on the cleaved caspase contents in the small intestine of weaned pigs challenged with enterotoxigenic Escherichia coli. (A) Cleaved caspase-3, cleaved cysteinyl aspartate-specific protease-3. (B) Cleaved caspase-8, cleaved cysteinyl aspartate-specific protease-8. (C) Cleaved caspase-9, cleaved cysteinyl aspartate-specific protease-9. a, b Means with different letters on vertical bars indicate significant differences (P < 0.05). Values are means (n = 8 pigs/treatment), with standard errors represented by vertical bars. CON: non-infected control (pigs received the basal diet and infused with sterilised Luria–Bertani culture); ETEC: ETEC-infected control (pigs received the basal diet and infused with enterotoxigenic Escherichia coli); ETEC + LMWC: pigs received the basal diet supplemented with 100 mg/kg low-molecular-weight chitosan and infused with enterotoxigenic Escherichia coli.