Although weaning stress has been reported to impair intestinal barrier function, the mechanisms have not yet been elucidated. In the present study, the intestinal morphology and permeability and mRNA expressions of tight junction proteins and cytokines in the intestine of piglets during the 2 wk after weaning were assessed. The phosphorylated (activated) ratios of p38, c-Jun NH(2)-terminal kinase (JNK), and extracellular regulated kinases (ERK1/2) were determined to investigate whether mitogen-activated protein kinase (MAPK) signaling pathways are involved in the early weaning process. A shorter villus and deeper crypt were observed on d 3 and 7 postweaning. Although damaged intestinal morphology recovered to preweaning values on d 14 postweaning, the intestinal mucosal barrier, which was reflected by transepithelial electrical resistance (TER) and paracellular flux of dextran (4 kDa) in the Ussing chamber and tight junction protein expression, was not recovered. Compared with the preweaning stage (d 0), jejunal TER and mRNA expressions of occludin and claudin-1 on d 3, 7, and 14 postweaning and Zonula occludens-1 (ZO-1) mRNA on d 3 and 7 postweaning were reduced, and paracellular flux of dextran on d 3, 7, and 14 postweaning was increased. An increase (P < 0.05) of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) mRNA on d 3 and d 7 postweaning and an increase (P < 0.05) of interferon-γ (IFN-γ) mRNA on d 3 postweaning were observed compared with d 0. No significant increase of transforming growth factor β1 (TGF-β1) and interleukin-10 (IL-10) mRNA after weaning was observed. The phosphorylated (activated) ratios of JNK and p38 on d 3 and 7 postweaning and the phosphorylated ratio of ERK1/2 on d 3 postweaning were increased (P < 0.05) compared with d 0. The results indicated that early weaning induced sustained impairment in the intestinal barrier, decreased mRNA expression of tight junction proteins, and upregulated the expression of proinflammatory cytokines, but anti-inflammatory cytokines were not affected in the intestine of piglets. The recovery of the intestinal barrier function was slower than that of the intestinal mucosal morphology. The weaning stress activated MAPK signaling pathways in the intestine, which may be an important mechanism of weaning-associated enteric disorders of piglets.

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One hundred-eighty piglets (Duroc × Landrace × Yorkshire), with an average initial weight of 7.4 kg weaned at 27 ± 1 days of age, were used to evaluate the effects of dietary zinc oxide-montmorillonite hybrid (ZnO-MMT) on growth performance, diarrhea, intestinal mucosal integrity, and digestive enzyme activity. All pigs were allotted to five treatments and fed with the basal diets supplemented with 0, 250, 500, and 750 mg/kg of Zn as ZnO-MMT or 2,000 mg/kg of Zn as ZnO. The results showed that supplementation with 500 or 750 mg/kg of Zn from ZnO-MMT and 2,000 mg/kg of Zn from ZnO improved average daily gain, enhanced average daily feed intake, decreased fecal scores at 4, 8, and 14 days postweaning, reduced intestinal permeability which was evident from the reduced lactulose recovery and urinary lactulose/mannitol ratio, and improved the activities of protease, amylase, lipase, trypsin, and chymotrypsin both in pancreas and small intestinal contents of pigs as compared with the control. Supplemental 250 mg/kg of Zn from ZnO-MMT also decreased fecal scores at 8 and 14 days postweaning, decreased urinary lactulose/mannitol ratio, and improved chymotrypsin activity in pancreas and small intestinal contents as well as protease activity in small intestinal contents compared with control. Moreover, the above indexes of weanling pigs fed with 500 or 750 mg/kg of Zn as ZnO-MMT did not differ from those fed with 2,000 mg/kg of Zn as ZnO. The results demonstrated that supplementation with 500 or 750 mg/kg of Zn from ZnO-MMT was as efficacious as 2,000 mg/kg of Zn from ZnO in improving growth performance, alleviating postweaning diarrhea, and enhancing intestinal mucosal integrity and the digestive enzyme activities in pancreas and small intestinal contents of pigs. The results that feeding lower concentrations of ZnO-MMT to weanling pigs maintained performance will be beneficial for the environment and for sustaining swine production.

A total of 450 one-day-old Arbor Acres male chickens were used to investigate the effects of zinc oxide-montmorillonite hybrid (ZnO-MMT) on growth performance, intestinal structure, and function. The birds were allotted to 5 dietary treatments for 21 d, each of which was replicated 6 times with 15 chicks per replicate. The dietary treatments were 1) corn-soybean meal diet (basal, containing 42.35 mg of Zn/kg); 2) basal diet + 600 mg of MMT/kg (equivalent to the MMT in the ZnO-MMT treatment); 3) basal diet + 60 mg of Zn/kg as ZnO; 4) basal diet + 60 mg of Zn/kg as ZnO-MMT; and 5) basal diet + 60 mg of Zn/kg as ZnSO(4)•7H(2)O. The results showed that chicks fed ZnO-MMT had higher (P < 0.05) ADG and feed intake than those fed the basal diet, MMT, or ZnO. Compared with the control, MMT, ZnO, or ZnSO(4), supplementation with ZnO-MMT decreased (P < 0.05) viable counts of Clostridium in small intestinal and cecal contents, increased (P < 0.05) colonic transepithelial electrical resistance (TER) values, and reduced (P < 0.05) colonic probe mannitol permeability as well as ileal or colonic inulin permeability. Compared with the control, supplemental ZnO-MMT increased (P < 0.05) villus height, the ratio of villus height to crypt depth at the small intestinal mucosa, the trypsin activity in the pancreas, and the digestive enzyme activities in small intestinal contents. Compared with the control, supplementation with ZnO increased (P < 0.05) the villus height and the villus height to crypt depth ratio at the duodenum. Supplementation with ZnSO(4) increased the trypsin activity in pancreas and small intestinal contents. However, supplemental MMT, ZnO, or ZnSO(4) did not affect (P > 0.05) growth performance, ileal and colonic barrier function, and intestinal microflora. The results indicated that supplementing 60 mg of Zn/kg as ZnO-MMT in broiler chickens improved growth performance, intestinal microflora, intestinal morphology, and barrier function as well as the digestive enzyme activities.