Biology and pathogenicity of Eimeria neodebliecki Vetterling, 1965 in experimentally infected pigs

The endogenous development and pathogenicity of Eimeria neodebliecki Vetterling, 1965 are described in weaned pigs inoculated with 250 000 oocysts. The endogenous stages developed within the apical cytoplasm of the enterocytes of the middle and posterior jejunum. The asexual development comprised two generations of meronts. Immature and mature meronts were found in groups up to five per host cell. The first fully developed macrogametes and mature microgamonts were seen at 9 days post-infection (DPI). The prepatent period was 10 days, and the patent period lasted 6–8 days. Sporulation of oocysts was completed within 12 days at 25°C, and 16 days at 20°C. E. neodebliecki infection produced clinical signs of coccidiosis in weaned pigs which developed frothy or mucoid diarrhea from 9 to 12 DPI. Pathological changes were situated in the second half of the small intestine, with the predilection for the posterior jejunum. At 9 and 10 DPI, macroscopically, ranged from catarrhal to focal, pseudomembranous inflammatory lesions. Histopathological and SEM examinations revealed moderate villous atrophy with focal epithelial erosions and fibrinonecrotic material at the villous tips. E. neodebliecki is pathogenic for pigs and can be associated with clinical manifestation of diarrhea, stunted growth and poor condition in pigs.     

An Enzyme Histochemical Investigation of the Intestinal Mucosa in Diarrheic Calves

Selected enzymes were examined in the small intestine of twelve 2–5 week-old calves, 8 with diarrhea and 4 convalescents. The diarrheic calves showed a reduction of enzyme reactions mainly in the duodenum and middle small intestine, and the crypt reactions appeared most severely affected. In the duodenum, villous alkaline phosphatase, adenosine triphosphate-(ATP)-splitting enzyme, and β-D-galactosidase were reduced in 3 calves; the reaction in the corresponding crypts was decreased in 6 calves for the ATP-splitting enzyme and in 4 calves for the β-D-galactosidase. Six calves showed decrease of villous brush border acid phosphatase, and 3 of villous non-specific esterase. In the middle jejunum, villous ATP-splitting enzyme was reduced in 3 calves, while 5 showed decrease of the corresponding crypt reaction. Convalescents had no enzyme reduction in the duodenum, whereas 1 showed marked reduction of the ATP-splitting enzyme and aminopeptidase in the middle and posterior jejunum. The decreased enzyme reactions in the present material may be caused by immaturity of epithelial cells associated with regenerative crypt hyperplasia and/or microbial destruction of enzymes.     

Effect of Weaning on Small Intestinal Structure and Function in the Piglet

Fifty-four piglets were selected from 12 litters weaned at 17 (Treatment 1), 21 (Treatment 2), 28 (Treatment 3) and 35 (Treatment 4) days old, respectively, to determine the effect of weaning age on small intestinal villus morphology, immunology and histochemistry. From proximal duodenum, proximal jejunum, distal jejunum and middle ileum, intestinal samples with three replicates (piglets) in each treatment were taken at 18, 22, 28 and 36; 22, 28, 36 and 43; 28, 36, 43, and 50; and 18, 22, 28, 36, 43 and 50d of age in Treatment 1, 2, 3 and 4, respectively. This was equivalent to 12h, 3d, 1 week, 2 week postweaning in Treatment 1; 12h, 1 week, 2 week, 3 week postweaning in Treatment 2 and 3, and all the same age in Treatment 4 as in Treatment 1, 2, 3, respectively. The results showed that villous height of duodenum and proximal jejunum decreased significantly in Treatment 1 and 3. Crypt depth in the duodenum, proximal jejunum and ileum also decreased significantly in Treatment 1. Date had significant effect on villous height of the duodenum, distal jejunum and ileum with the shortest on day 29 and crypt depth of all positions increased with piglet age except the crypt depth in proximal jejunum decreased on day 50. Weaning age and day of age had significant effects on intraepithelial lymphocyte (IEL) number and goblet cell (GC) number at all positions of small intestinal mucosa in piglets. The number of IEL at all segments of small intestinal mucosa in Treatment 3 increased significantly compared to those in other treatments, but IEL number at all locations of small intestinal mucosa in Treatment 2 decreased significantly compared to those in other treatments. The number of GC in small intestinal mucosa increased significantly in early-weaned (< day 21) piglets. It appears that providing fluid milk replacer for a few days postweaning could dramatically reduce the negative impact of weaning on villous morphology and digestive and absorptive function, especially in pigs weaned prior to 3 week of age. Finally, as weaning age was reduced, GC had a greater role in intestinal duct protection.     

Viremia and nasal and rectal shedding of rotavirus in gnotobiotic pigs inoculated with Wa human rotavirus

Respiratory symptoms with rotavirus shedding in nasopharyngeal secretions have been reported in children with and without gastrointestinal symptoms (Zheng et al., 1991, J. Med. Virol. 34:29-37). To investigate if attenuated and virulent human rotavirus (HRV) strains cause upper respiratory tract infections or viremia in gnotobiotic pigs, we inoculated them with attenuated or virulent HRV intranasally, intravenously, or orally or via feeding tube (gavage) and assayed virus shedding. After oral or intranasal inoculation with attenuated HRV, the pigs remained asymptomatic, but 79 to 95% shed virus nasally and 5 to 17% shed virus rectally. After inoculation by gavage, no pigs shed virus nasally or rectally, but all pigs seroconverted with antibodies to HRV. No viremia was detected through postinoculation day 10. Controls inoculated intranasally with nonreplicating rotavirus-like particles or mock inoculated did not shed virus. In contrast, 100% of pigs inoculated with virulent HRV (oral, intranasal, or gavage) developed diarrhea, shed virus nasally and rectally, and had viremia. The infectivity of sera from the viremic virulent HRV-inoculated pigs was confirmed by inoculating gnotobiotic pigs orally with pooled HRV-positive serum. Serum-inoculated pigs developed diarrhea and fecal and nasal virus shedding and seroconverted with serum and intestinal HRV antibodies. Pigs inoculated intravenously with serum or intestinal contents from the viremic virulent HRV-inoculated pigs developed diarrhea, virus shedding, and viremia, similar to the orally inoculated pigs. This study provides new evidence that virulent HRV causes transient viremia and upper respiratory tract infection in addition to gastrointestinal infection in gnotobiotic pigs, confirming previous reports of rotavirus antigenemia (Blutt et al., Lancet 362:1445-1449, 2003). Our data also suggest that intestinal infection might be initiated from the basolateral side of the epithelial cells via viremia. Additionally, virus shedding patterns indicate a different pathogenesis for attenuated versus virulent HRV.     

Binding patterns of human norovirus-like particles to buccal and intestinal tissues of gnotobiotic pigs in relation to A/H histo-blood group antigen expression

Histo-blood group antigen (HBGA) phenotypes have been associated with susceptibility to human noroviruses (HuNoVs). Our aims were: (i) to determine the patterns of A/H HBGA expression in buccal and intestinal tissues of gnotobiotic (Gn) pigs; (ii) to determine if virus-like particles (VLPs) of HuNoV genogroup I (GI) and GII bind to A- or H-type tissues; (iii) to compare A/H expression and VLP binding patterns and confirm their binding specificities by blocking assays; (iv) to develop a hemagglutination inhibition test using buccal cells from live pigs to determine the Gn pig's A/H phenotype and to match viral strains with previously determined HuNoV VLP binding specificities; and (v) to determine the A/H phenotypes and compare these data to the infection outcomes of a previous study of 65 Gn pigs inoculated with HuNoV GII/4 strain HS66 and expressing A and/or H or neither antigen on their buccal and intestinal tissues (S. Cheetham, M. Souza, T. Meulia, S. Grimes, M. G. Han, and L. J. Saif, J. Virol. 80:10372-10381, 2006). We found that the HuNoV GI/GII VLPs of different clusters bound to tissues from four pigs tested (two A+ and two H+). The GI/1 and GII/4 VLPs bound extensively to duodenal and buccal tissues from either A+ or H+ pigs, but surprisingly, GII/1 and GII/3 VLPs bound minimally to the duodenum of an A+ pig. The VLP binding was partially inhibited by A-, H1-, or H2-specific monoclonal antibodies, but was completely blocked by porcine mucin. Comparing the A/H phenotypes of 65 HS66-inoculated Gn pigs from our previous study, we found that significantly more A+ and H(+) pigs (51%) than non-A+ and non-H+ pigs (12.5%) shed virus. From the 22 convalescent pigs, significantly more A+ or H+ pigs (66%) than non-A+ or H+ pigs (25%) seroconverted.     

PAT-1 (Slc26a6) is the predominant apical membrane Cl-/HCO3- exchanger in the upper villous epithelium of the murine duodenum

Basal HCO(3)(-) secretion across the duodenum has been shown in several species to principally involve the activity of apical membrane Cl(-)/HCO(3)(-) exchanger(s). To investigate the identity of relevant anion exchanger(s), experiments were performed using wild-type (WT) mice and mice with gene-targeted deletion of the following Cl(-)/HCO(3)(-) exchangers localized to the apical membrane of murine duodenal villi: Slc26a3 [down-regulated in adenoma (DRA)], Slc26a6 [putative anion transporter 1 (PAT-1)], and Slc4a9 [anion exchanger 4 (AE4)]. RT-PCR of the isolated villous epithelium demonstrated PAT-1, DRA, and AE4 mRNA expression. Using the pH-sensitive dye BCECF, anion exchange rates were measured across the apical membrane of epithelial cells in the upper villus of the intact duodenal mucosa. Under basal conditions, Cl(-)/HCO(3)(-) exchange activity was reduced by 65-80% in the PAT-1(-) duodenum, 30-40% in the DRA(-) duodenum, and <5% in the AE4(-) duodenum compared with the WT duodenum. SO(4)(2-)/HCO(3)(-) exchange was eliminated in the PAT-1(-) duodenum but was not affected in the DRA(-) and AE4(-) duodenum relative to the WT duodenum. Intracellular pH (pH(i)) was reduced in the PAT-1(-) villous epithelium but increased to WT levels in the absence of CO(2)/HCO(3)(-) or during methazolamide treatment. Further experiments under physiological conditions indicated active pH(i) compensation in the PAT-1(-) villous epithelium by combined activities of Na(+)/H(+) exchanger 1 and Cl(-)-dependent transport processes at the basolateral membrane. We conclude that 1) PAT-1 is the major contributor to basal Cl(-)/HCO(3)(-) and SO(4)(2-)/HCO(3)(-) exchange across the apical membrane and 2) PAT-1 plays a role in pH(i) regulation in the upper villous epithelium of the murine duodenum.     

Alternative migration routes of Ascaris suum in the pig

Experiments were conducted to investigate possible alternative routes of extraintestinal migration of Ascaris suum larvae in the pig. Pigs were infected with A. suum via injection of newly hatched larvae into cecal veins (i.v.), into cecal lymph nodes (LN), or intraperitoneally (i.p.), and control animals were inoculated orally with infective eggs (p.o.). Two pigs per inoculation route were necropsied on days 1, 4, and 13 postinoculation. The numbers of liver lesions and the percentage of larvae recovered was considerably greater in pigs inoculated i.v. or p.o. on each necropsy day. However, irrespective of inoculation route, at least a proportion of larvae passed through the livers and were able to complete migration to the small intestine by day 13. The results indicate that larval penetration of the intestinal wall is not necessary for liver-lung migration and that passage through the liver may be favorable for migrating A. suum larvae, although a delayed arrival in the small intestine cannot be ruled out for larvae following alternative routes.     

Systematic and intestinal antibody-secreting cell responses and correlates of protective immunity to human rotavirus in a gnotobiotic pig model of disease.

Neonatal gnotobiotic pigs orally inoculated with virulent (intestinal-suspension) Wa strain human rotavirus (which mimics human natural infection) developed diarrhea, and most pigs which recovered (87% protection rate) were immune to disease upon homologous virulent virus challenge at postinoculation day (PID) 21. Pigs inoculated with cell culture-attenuated Wa rotavirus (which mimics live oral vaccines) developed subclinical infections and seroconverted but were only partially protected against challenge (33% protection rate). Isotype-specific antibody-secreting cells (ASC were enumerated at selected PID in intestinal (duodenal and ileal lamina propria and mesenteric lymph node [MLN]) and systemic (spleen and blood) lymphoid tissues by using enzyme-linked immunospot assays. At challenge (PID 21), the numbers of virus-specific immunoglobulin A (IgA) ASC, but not IgG ASC, in intestines and blood were significantly greater in virulent-Wa rotavirus-inoculated pigs than in attenuated-Wa rotavirus-inoculated pigs and were correlated (correlation coefficients: for duodenum and ileum, 0.9; for MLN, 0.8; for blood, 0.6) with the degree of protection induced. After challenge, the numbers of IgA and IgG virus-specific ASC and serum-neutralizing antibodies increased significantly in the attenuated-Wa rotavirus-inoculated pigs but not in the virulent-Wa rotavirus-inoculated pigs (except in the spleen and except for IgA ASC in the duodenum). The transient appearance of IgA ASC in the blood mirrored the IgA ASC responses in the gut, albeit at a lower level, suggesting that IgA ASC in the blood of humans could serve as an indicator for IgA ASC responses in the intestine after rotavirus infection. To our knowledge, this is the first report to study and identify intestinal IgA ASC as a correlate of protective active immunity in an animal model of human-rotavirus-induced disease.     

Stereological studies on the small intestinal epithelium of the rat

Summary Quantitative macroscopic, light-microscopic and electron-microscopic studies were performed on the small intestine of fasted and non-fasted adult, male Sprague-Dawley rats. In non-fasted rats the small intestine was longer than in fasted rats. Due to the presence of villi the surface area in the duodenum and the jejunum was enlarged about six times. The microvilli on the villous crests caused a surface enlargement by 13 times in the duodenum (value corrected for overestimation due to section thickness), and 19 times in the jejunum of the fasted rats. At the base of the villi these values were about 50% lower. It was calculated that, in the fasted rats, the total enlargement of the luminal surface area — due to villi and microvilli — was 63 times in the duodenum and 81 times in the jejunum (corrected for section thickness).Differences between the villous crest epithelium and the villous base epithelium were also found with regard to the mean cell height, and the volume densities of the absorptive cell nuclei, the mitochondria, and the paracellular channels.Supported by grants from the Swedish Medical Research Council (Project No. 12X-2298), from the Swedish Group-Insurance Co. Förenade Liv, from Tore Nilson's Fund for Medical Research and from the Medical Faculty, University of Umeå     

Small bowel biopsy for malabsorption: comparison of the diagnostic adequacy of endoscopic forceps and capsule biopsy specimens.

Biopsy specimens of the small bowel were obtained from 40 patients suspected of having malabsorption. Four different techniques were used at a single session--namely, endoscopic biopsy of the descending duodenum using paediatric and standard size forceps and suction capsule biopsy of the descending duodenum and the proximal jejunum. Specimens were compared for size, adequacy, and ability to confirm or exclude mucosal abnormality. Fourteen patients had villous atrophy. In all patients four biopsy specimens were obtained with paediatric endoscopic forceps and four with standard endoscopic forceps. No capsule biopsy specimen was retrieved from the duodenum in three patients and from the jejunum in five patients. Specimens were considered to be adequate in 36 patients when paediatric forceps were used, in 39 when standard forceps were used, in 28 on duodenal capsule biopsy, and in 32 on jejunal capsule biopsy. This study indicates that the most reliable method for diagnosing or excluding villous atrophy is endoscopic forceps biopsy of the descending duodenum, provided that at least four specimens are obtained with standard size forceps.     

Intranasal administration of 2/6-rotavirus-like particles with mutant Escherichia coli heat-labile toxin (LT-R192G) induces antibody-secreting cell responses but not protective immunity in gnotobiotic pigs

We investigated the immunogenicity of recombinant double-layered rotavirus-like particle (2/6-VLPs) vaccines derived from simian SA11 or human (VP6) Wa and bovine RF (VP2) rotavirus strains. The 2/6-VLPs were administered to gnotobiotic pigs intranasally (i.n.) with a mutant Escherichia coli heat-labile toxin, LT-R192G (mLT), as mucosal adjuvant. Pigs were challenged with virulent Wa (P1A[8],G1) human rotavirus at postinoculation day (PID) 21 (two-dose VLP regimen) or 28 (three-dose VLP regimen). In vivo antigen-activated antibody-secreting cells (ASC) (effector B cells) and in vitro antigen-reactivated ASC (derived from memory B cells) from intestinal and systemic lymphoid tissues (duodenum, ileum, mesenteric lymph nodes [MLN], spleen, peripheral blood lymphocytes [PBL], and bone marrow lymphocytes) collected at selected times were quantitated by enzyme-linked immunospot assays. Rotavirus-specific immunoglobulin M (IgM), IgA, and IgG ASC and memory B-cell responses were detected by PID 21 or 28 in intestinal and systemic lymphoid tissues after i.n. inoculation with two or three doses of 2/6-VLPs with or without mLT. Greater mean numbers of virus-specific ASC and memory B cells in all tissues prechallenge were induced in pigs inoculated with two doses of SA11 2/6-VLPs plus mLT compared to SA11 2/6-VLPs without mLT. After challenge, anamnestic IgA and IgG ASC and memory B-cell responses were detected in intestinal lymphoid tissues of all VLP-inoculated groups, but serum virus-neutralizing antibody titers were not significantly enhanced compared to the challenged controls. Pigs inoculated with Wa-RF 2/6-VLPs (with or without mLT) developed higher anamnestic IgA and IgG ASC responses in ileum after challenge compared to pigs inoculated with SA11 2/6-VLPs (with or without mLT). Three doses of SA 11 2/6-VLP plus mLT induced the highest mean numbers of IgG memory B cells in MLN, spleen, and PBL among all groups postchallenge. However, no significant protection against diarrhea or virus shedding was evident in any of the 2/6-VLP (with or without mLT)-inoculated pigs after challenge with virulent Wa human rotavirus. These results indicate that 2/6-VLP vaccines are immunogenic in gnotobiotic pigs when inoculated i.n. and that the adjuvant mLT enhanced their immunogenicity. However, i.n. inoculation of gnotobiotic pigs with 2/6-VLPs did not confer protection against human rotavirus challenge.     

Rumenectomy-induced proliferation in duodenal villous epithelium is mechanistically related to the disappearance of statin, a non-proliferation-specific nuclear protein

We undertook this study to determine the effect of rumenectomy (a known cause of duodenal crypt cell hyperplasia) on the epithelial growth kinetics of the crypt-villus axis in rat duodenum. Ten rats were randomly assigned to control (gastrotomy) and experimental (rumenectomy) groups. After 14 days rats were sacrificed and representative sections were stained with the monoclonal antibody to statin, a non-proliferation-specific protein, by the immunoperoxidase procedure. In the control group, the mean percentages of statin-positive cells in the proximal duodenum, distal duodenum, proximal jejunum, and distal jejunum were 79 +/- 8.5, 79.5 +/- 5.7, 85 +/- 1.4, and 83.5 +/- 0.7, respectively. In the rumenectomy group, statin-positive nuclei were found in the region of the villous apices only, and the corresponding values for the above four areas were 26.2 +/- 4.9, 24.5 +/- 3.5, 31.7 +/- 4.5, and 80.5 +/- 2.1. Except for distal jejunum, the differences in statin expression in the control and experimental groups were significant (p less than 0.001). Rumenectomy leads to the disappearance of statin from the villous column cells of the duodenum and proximal small bowel. The lack of expression of statin in the rumenectomy group documents the potential usefulness of this measure in future studies in neoplasia were understanding of the proliferative status is of crucial importance.     

Cytokine and antibody responses in gnotobiotic pigs after infection with human norovirus genogroup II.4 (HS66 strain)

A human norovirus genogroup II.4 strain HS66 (HuNoV-HS66) infects and causes mild diarrhea in gnotobiotic (Gn) pigs (S. Cheetham, M. Souza, T. Meulia, S. Grimes, M. G. Han, and L. J. Saif, J. Virol. 80:10372-10381, 2006). In this study we evaluated systemic and intestinal humoral and cellular immune responses to HuNoV-HS66 in orally inoculated pigs. Antibodies and type I interferon (IFN-I or IFN-alpha), proinflammatory interleukin-6 (IL-6), Th1 (IL-12 and IFN-gamma), Th2 (IL-4), and Th2/regulatory T ([T(reg)] IL-10) cytokine profiles in serum and intestinal contents (IC) of the HuNoV-HS66-inoculated pigs and controls were assessed by enzyme-linked immunosorbent assay at selected postinoculation days (0 to 28). Using an enzyme-linked immunospot assay, we evaluated immunoglobulin M (IgM), IgA, and IgG antibody-secreting cells (ASC) and cytokine-secreting cells (CSC) in intestine, spleen, and blood. In the HuNoV-inoculated pigs, antibody titers in serum and IC were generally low, and 65% seroconverted. Pigs with higher diarrhea scores were more likely to seroconvert and developed higher intestinal IgA and IgG antibody titers. The numbers of IgA and IgG ASC were higher systemically than in the gut. In serum, HuNoV induced persistently higher Th1 (low transient IFN-gamma and high IL-12) than the other cytokines, but also low Th2 (IL-4) and Th2/T(reg) (IL-10) levels; low, transient proinflammatory (IL-6) cytokines; and, notably, a delayed IFN-alpha response. In contrast, intestinal innate (IFN-alpha early and late) and Th1 (IL-12 late) cytokines were significantly elevated postinfection. HuNoV-HS66 also elicited higher numbers of Th1 (IL-12 and IFN-gamma) CSC than Th2 (IL-4) and proinflammatory (IL-6) CSC, with the latter responses low in blood and intestine, reflecting low intestinal inflammation in the absence of gut lesions. These data provide insights into the kinetics of cytokine secretion in serum and IC of HuNoV-inoculated Gn pigs and new information on intestinal humoral and cellular immune responses to HuNoV that are difficult to assess in human volunteers.     

Regional variation in ontogeny of class II antigens in enterocytes of mouse small intestine.

The ontogeny of major histocompatibility class II antigens in small intestine enterocytes of postnatal C3H/He mice was investigated. Cryosections of duodenal, jejunal, and ileal segments from 7-, 14-, 16-, 20-, 21-, 23-, 25-, 27-, 28-day-old and 7-week-old mice were stained for the class II antigens with MRC OX6 monoclonal antibodies by peroxidase-antiperoxidase labelling. In adults, the duodenum exhibited least expression of class II antigens that increased progressively towards the ileum. The expression in the villous epithelium was first seen in the duodenum and jejunum 21 days after birth but the ileal enterocytes did not exhibit any class II antigens. The earliest appearance (21 days postnatal) of class II antigens in the enterocytes coincides with the age of weaning which suggests that immunologic stimulation by ingested antigens after weaning may influence expression of these antigens. At day 28 after birth, the duodenum and jejunum expressed levels comparable to those in the adults. The first expression of the antigens seen in the ileum was at day 28 postpartum. Crypt epithelium of the three regions of the small intestine showed expression similar to that of corresponding regional villous enterocytes. We conclude that there is an age-dependent regional variation in the expression of class II antigens in enterocytes, and the expression increases with age. The variation in expression of the class II antigens in enterocytes of postnatal mice is attributed to the developmental status of the tissue. The nature of postnatal expression of the antigens is important since an early appearance of these antigens may have implications in autoimmunity.     

Gluten-sensitive enteropathy in a cynomolgus monkey

A malabsorption syndrome was observed in a cynomolgus macaque. Clinical signs included weight loss despite increased appetite, and diarrhea, characterized by an increased volume of soft, tan, malodorous feces. Clinicopathologic findings included hypoalbuminemia, generalized dilation of bowel loops with a prolonged transit time, steatorrhea and markedly diminished absorption of D-xylose. Biopsies of the duodenum and jejunum had total villous atrophy, crypt hyperplasia and a plasmacytic-lymphocytic infiltrate of the lamina propria. The monkey's diet was changed to a semi-synthetic diet containing no grain products. Subsequently, stool characteristics, body weight and intestinal villous morphology returned to normal. This response to removal of grain products from the diet suggests a syndrome similar to gluten-sensitivity enteropathy in human beings.     

Dietary alanyl-glutamine improves growth performance of weaned piglets through maintaining intestinal morphology and digestion–absorption function

Alanyl-glutamine (Ala-Gln), a highly soluble and stable glutamine dipeptide, is known to improve gut integrity and function. The aim of this study was to evaluate whether dietary Ala-Gln supplementation could improve growth performance, intestinal development and digestive-absorption function in weaned piglets. A total of 100 purebred Yorkshire piglets weaned at 21 days of age were assigned randomly to four dietary treatment groups and fed a basal diet (control group) or a basal diet containing 0.15%, 0.30% and 0.45% Ala-Gln, respectively. Compared with the control group, piglets fed the Ala-Gln diets had higher average daily gain and lower feed : gain and diarrhea rate (P < 0.05). Moreover, dietary Ala-Gln supplementation increased villous height and villous height : crypt depth ratio in duodenum and jejunum (P < 0.05), as well as the activities of maltase and lysozyme in jejunum mucosa (P < 0.05). In addition, a decrease in serum diamine oxidase activity and crypt depth in duodenum and jejunum was observed in piglets fed the Ala-Gln diets (P < 0.05). Serum cytosolic phospholipase A2 (cPLA2) concentration and gene expression of cPLA2, Na⁺-dependent glucose transporter 1, glucose transporter 2 and peptide transporter 1 in jejunum were increased by feeding Ala-Gln diets relative to control diet (P < 0.05). These results indicated that feeding Ala-Gln diet has beneficial effects on the growth performance of weaned piglets, which associated with maintaining intestinal morphology and digestive-absorption function.