Intestinal epithelial homeostasis plays an important role in intestinal morphology and function. However, the developmental changes in intestinal epithelial cell turnover in piglets during early weaning are unknown so far. Thus, the aim of this work was to detect changes in piglet gut development from weaning to post-weaning d 14. Accordingly, 40 piglets were used in the present study, and 8 piglets were randomly selected for sampling at d 0, 1, 3, 7 and 14 post-weaning, respectively. The results showed that weaning stress significantly affected small intestinal morphological architecture, and this impact was the worst on d 3, and then returned to normal on d 14. Furthermore, the number of the marker of proliferation Ki-67 (Ki67) positive cells was decreased on d 1 and 3, and then recovered on d 14 (P < 0.001). Also, weaning strikingly increased jejunal epithelial cell shedding on d 1 to 7 compared on d 0 (P < 0.05). Moreover, weaning remarkably affected the number of small intestinal enterocytes, goblets and endocrine cells (P < 0.05), and there were also significant differences in genes expression related to proliferation and differentiation (P < 0.05). Additionally, the mechanistic target of rapamycin (mTOR) phosphorylation level was higher on d 3 (P < 0.05). However, the Wingless/Int1 (WNT)/β-catenin pathway was not influenced by post-weaning days. Taken together, weaning induced noteworthy changes in intestinal epithelial cell proliferation, differentiation and shedding, and the mTOR signaling pathway was involved in this process. Our findings provide a cellular mechanism for intestinal developmental changes during weaning periods. This may provide nutritionists with better insight into designing efficient in-feed alternatives for preventing the unfavorable gut development in weaning piglets.

Epidermal growth factor (EGF) has been shown to improve piglet intestinal morphology and epithelial recovery. In an attempt to further understand the mechanisms behind these improvements, this study tested the hypothesis that dietary EGF may affect intestinal morphology by stimulating the proliferation and differentiation of enterocytes in weaning piglets. In piglets receiving 200 µg kg−1 EGF, crypt depth and villus height increased (P<0.05). Adding 400 µg kg−1 EGF increased villus height-to-crypt depth ratio (P<0.05), but reduced crypt depth (P<0.05). Dietary supplementation with 200 µg kg−1 EGF significantly increased the number of Ki67-positive cells (P<0.01) and tended to increase the mRNA level of proliferating cell nuclear antigen (P<0.10). However, this supplementation decreased the expression level of intestinal fatty acid-binding protein (P<0.05). Piglets fed with 400 µg kg−1 EGF had an increased mRNA level of intestinal alkaline phosphatase (P<0.05). The phosphorylation of mTOR (mammalian target of rapamycin) was observed in the 200 µg kg−1 EGF group. These results suggest that dietary supplementation with a low level of EGF improved piglet intestinal morphology through stimulating the proliferation and differentiation of enterocytes, and the mTOR signaling pathway may partly be involved in this process.

The abnormalities in intestinal morphology and digestive function during weaning are associated with the loss of milk-borne growth factors. Epidermal growth factor (EGF) has been shown to stimulate the growth of animals. This study was to determine the effect of dietary EGF on nutrient digestibility, intestinal development and the expression of genes encoding nutrient transporters in weaned piglets. Forty-two piglets were weaned at 21 days and assigned to one of three treatment groups: (1) basal diet (control), (2) basal diet + 200 µg/kg EGF or (3) basal diet + 400 µg/kg EGF. Each treatment consisted of 14 replicates, and seven piglets from each treatment were sampled on day 7 and 14. The EGF supplementation significantly elevated (p < 0.05) the coefficients of total tract apparent digestibility of crude protein, calcium and phosphorus, but tended to decrease sucrase activity (p < 0.10) than the control group. At day 7 post-weaning, animals receiving EGF diets showed a tendency (p < 0.10) towards greater ileal villus height (VH), jejunal crypt depth (CD) and duodenal VH:CD when compared with the control group. Moreover, the mRNA levels of glucose transporter 2 (Slc2a2), neutral amino acid transporter (Slc6a19) and calbindin D9k (S100G) tended to be higher (p < 0.10) for EGF groups than the control group. By day 14, EGF supplementation markedly enhanced (p < 0.05) the VH, CD and VH:CD in the jejunum compared to the control group. This addition also up-regulated (p < 0.05) the mRNA level and the protein abundance of peptide transporter 1 than the control group. These findings demonstrated that dietary EGF beneficially enhanced nutrient digestibility, improved intestinal development and increased the mRNA expression of nutrient transporters in weaned piglets.

Oxidative stress is more likely to occur in the intestine compared to other organs because it is located at the interface between an organism and its luminal environment. Tannic acid (TA) is reported to serve as an antioxidant, antimicrobial, anticarcinogenic and antimutagenic agent in various models. In the present study, we evaluated the effects of TA on body weight, intestinal morphology, antioxidative activity, and intestinal barrier in diquat-induced oxidative stress mouse model. The results showed that TA had failed to affect antioxidative enzymes in diquat-challenged mice, while the concentration of 2.5 mg kg(-1) to 10 mg kg(-1) TA had no negative effect on body weight and enhanced the colon length in mice. The dose of 2.5 mg kg(-1) TA ameliorated the morphological damage in the jejunum by increasing the villus height and crypt depth, activated the antioxidative pathway by decreasing jejunal protein expression of Kelch like-ECH-associated protein 1 (KEAP1) and increasing protein expression of Nuclear factor erythroid 2-related factor 2 (NRF2), and affected the intestinal barrier by inhibiting the jejunal mRNA expression of claudin and promoting mRNA expression of zonula occludens (zo-1). In conclusion, the pretreatment of TA in a mouse model of oxidative stress failed to change the antioxidative enzymes but modulated the jejunal morphology, colon length, antioxidative pathway and intestinal barrier in the diquat oxidative model.

Weaning process widely affects the small intestinal structure and function in piglets, while the responses of large intestine to weaning stress are still obscure. The purpose of this study was to determine the developmental changes (i.e., short chain fatty acids (SCFAs) concentrations, growth parameters, crypt-related indices and antioxidant capacity) in colon of piglet during weaning. Forty piglets were weaned at day 21 and euthanized to collect colonic tissues and digesta samples on day 0, 1, 3, 7 and 14 post-weaning (n = 8). Piglet growth performance was improved (p < .001) on day 7 and 14 post-weaning. The concentrations of acetate, propionate, butyrate, valerate, isobutyrate, isovalerate and total SCFAs were higher (p < .001) during the late post-weaning period. The mRNA abundances of SCFAs transporters were greater (p < .001) on day 7 and 14. The absolute and relative weights, absolute length and perimeter of colon were greater (p < .001) on day 7 and 14. Similarly, post-weaning increases (p < .001) in colonic crypt depth and Ki67 positive cells numbers per crypt were observed during the same period. Colonic crypt fission indices decreased (p < .01), while total crypt numbers increased (p < .001) on day 14 after weaning. Moreover, total SCFAs concentration was significantly associated with colonic growth parameters and Ki67 cells/crypt (p < .001). In addition, catalase content was decreased on day 3, 7, and 14, whereas, the concentrations of total superoxide dismutase (T-SOD) and manganese-containing superoxide dismutase (MnSOD) were higher (p < .05) on day 1 and 3 post-weaning. These results showed that weaning process has a significant effect on colonic growth and development, which might be associated with the change of SCFAs concentrations in colon.

Enterotoxigenic Escherichia coli K88 (E. coli K88) are considered as a major cause of diarrhea and death in newly weaned piglets. Oral passive immunization with chicken egg yolk immunoglobulins (IgY) have attracted considerable attention for treatment of gastrointestinal infection due to its high specificity. In this study it was estimated the protective effect of anti-K88 fimbriae IgY against E. coli K88 adhesion to piglet intestinal mucus in vitro and to investigate the potential use of IgY for controlling E. coli-induced diarrhea in weaned piglets in vivo. E. coli K88 was incubated with IgY for 24 h, and the bacterial growth profiles showed that specific IgY with a concentration higher than 5 mg/mL was observed to significantly inhibit the growth of E. coli K88 compared to nonspecific yolk powder in a liquid medium. Moreover, pretreatment with 50 mg/mL of IgY was found to significantly decrease the adhesion ability of E. coli K88 to porcine jejunal and ileal mucus, further supported by the observations from our immunofluorescence microscopic analysis. In vivo, administration of IgY successfully protected piglets from diarrhea caused by E. coli K88 challenge. Additionally, IgY treatment efficiently alleviated E. coli-induced intestinal inflammation in piglets as the gene expression levels of inflammatory cytokines TNF-α, IL-22, IL-6 and IL-1β in IgY-treated piglets remained unchanged after E. coli K88 infection. Furthermore, IgY significantly prevented E. coli K88 adhering to the jejunal and ileal mucosa of piglets with E. coli infection and significantly decreased E. coli and enterotoxin expression in colonic contents. Outcome of the study demonstrated that IgY against the fimbrial antigen K88 was able to significantly inhibit the growth of E. coli K88, block the binding of E. coli to small intestinal mucus, and protect piglets from E. coli-induced diarrhea. These results indicate that passive immunization with IgY may be useful to prevent bacterial colonization and to control enteric diseases due to E. coli infection. The study has great clinical implication to provide alternative therapy to antibiotics in E coli induced diarrhea.

本试验旨在研究饲粮中添加表皮生长因子(EGF)对断奶仔猪血清生化指标、血清游离氨基酸和小肠黏膜水解氨基酸含量的影响.选取体重相近、健康的21日龄断奶仔猪42头,随机分成3组,每组14个重复,每个重复1头仔猪.Ⅰ组为对照组,饲喂基础饲粮;Ⅱ组和Ⅲ组分别饲喂在基础饲粮中添加200和400μg/kg EGF的试验饲粮.试验期为14 d.结果表明:1)饲粮中添加EGF对断奶仔猪平均日增重、平均日采食量和料重比没有显著影响(P＞0.05).2)断奶后7d,Ⅱ组血清尿酸含量显著高于Ⅰ组(P＜0.05),而Ⅱ组和Ⅲ组血清免疫球蛋白A含量显著低于Ⅰ组(P＜0.05).断奶后14 d,Ⅲ组血清肌酐含量显著低于Ⅰ组(P＜0.05),且Ⅲ组血清谷草转氨酶/谷丙转氨酶值显著低于Ⅰ组和Ⅱ组(P＜0.05).饲粮中添加EGF对断奶仔猪血清尿素氮、葡萄糖、总蛋白、白蛋白、球蛋白、免疫球蛋白M、免疫球蛋白G、胰岛素样生长因子-1、生长激素含量,白蛋白/球蛋白,谷草转氨酶、谷丙转氨酶活性没有显著影响(P＞0.05).3)断奶后7d,Ⅱ组血清牛磺酸、丙氨酸、瓜氨酸和组氨酸含量显著低于Ⅲ组(P＜0.05),Ⅱ组血清精氨酸、谷氨酸和丝氨酸含量显著低于Ⅰ组和Ⅲ组(P＜0.05),各组之间其他血清氨基酸含量无显著差异(P＞0.05).4)断奶后14d,与Ⅰ组和Ⅲ组比,Ⅱ组空肠黏膜缬氨酸和回肠黏膜半胱氨酸含量显著升高(P＜0.05),Ⅱ组空肠黏膜丝氨酸、谷氨酸、丙氨酸、半胱氨酸、异亮氨酸、苯丙氨酸和组氨酸含量也有升高趋势(P＜0.10).综上所述,饲粮中添加高剂量EGF能够降低断奶仔猪血清免疫球蛋白A等生化指标含量,而饲粮中添加低剂量EGF能够降低血清和小肠黏膜部分氨基酸含量.

The object of this study was to investigate the effects of oral administration with glutamate on organ indices, blood biochemical indexes, blood lipid levels and antioxidant capacities of the suckling piglets. Forty-eight healthy pig-lets (Duroc × Large White × Landrace;1 d of age) with similar initial weight and birth date (1. 55 ± 0. 20 kg;1 d of age) were selected from six sows (8 piglets per sow) and randomly assigned to 4 dietary groups in terms of body weight (BW). Pigltes were marked by ear tags after birth. The piglets were oral administration with 0. 18 g/kg BW of sodium chloride (CN group), 0. 06 g/kg BW monosodium glutamate (LMG group), 0. 50 g/kg BW monosodium glutamate ( MMG group) and 1. 00 g/kg BW monosodium glutamate ( HMG group) , respectively. On day 7 of the trial, one piglet was randomly selected from each group, and the samples were collected after blood collection, and the others were slaughtered on the day 21. The results showed that there were no significant differences on the heart, liver, spleen and kidney index at day 7 and day 21. Oral administration with high dose of glutamate increased serum glutamine synthetase activity and hemoglobin content in suckling piglets on day 7 as well as serum glutamine synthetase activity on day 21. Serum endotoxin ET content and ATPase activity in sucking piglets were significantly reduced by oral administration with high dose of glutamate. Oral administration with medium dose of glutamate reduced the serum free fatty acid content on day 7 and 21, and also affected the serum HDL levels on 21 days. Oral administration with medium dose of glutamate increased serum total antioxidant capacity and reduced the activities of serum glutathione transferase and superoxide dis-mutase and the content of malondialdehyde on day 7. On day 21, the MMG and HMG groups had lower serum glutathi-one transferase activity and malondialdehyde content and greater serum superoxide dismutase activity than CN group. The results of the present experiment indicate that oral administration with glutamate can affect blood biochemical indices, blood lipid levels and improve the antioxidant capacities of suckling piglets.

Understanding the regulatory mechanisms of intestinal morphology and function is essential for improving postweaning growth in pigs. The objective of this study was to identify the relationships of enterocyte proliferation with intestinal villus height, crypt depth, and nutrient digestibility in piglets. Sixty-four 21-d-old weaned piglets were used. Gastrointestinal cell proliferation was evaluated via Ki-67 immunohistochemistry. Villus height and crypt depth were measured using hematoxylin and eosin (H&E)-stained sections. The apparent total tract digestibility (ATTD) of CP and GE was determined by chemical analysis. The activities of lactase and sucrase were determined with commercial kits. Western blot was carried out to assess the expression of nutrient transporters. The number of Ki-67 positive cells was associated with villus height (r = 0.548, P < 0.001) and crypt depth (r = 0.759, P < 0.001) in the jejunum. The number of Ki-67 positive cells was also associated with the ATTD of CP (r = 0.715, P = 0.001). Furthermore, a positive relationship between Ki-67 positive cell populations and lactase activity (r = 0.559, P < 0.001) was observed. Additionally, the number of Ki-67 positive cells was associated with the protein expression levels of nutrient transporters PEPT1 (r = 0.511, P = 0.030) and SGLT1 (r = 0.601, P = 0.014). Weak relationships were found between Ki-67 positive cell numbers and the ATTD of GE (r = 0.401, P = 0.099) and the activity of sucrase (r = 0.313, P = 0.087). In conclusion, enterocyte proliferation was positively associated with intestinal villus height, crypt depth, and nutrient digestibility in weaning piglets. Our findings suggested that intestinal morphology and function can be improved by regulating epithelial cell proliferation in piglets.