The effects of dietary sulfur amino acids on growth performance, intestinal morphology, enzyme activity, and nutrient transporters in weaning piglets

Development of small intestinal barrier function and underlying mechanism in Chinese indigenous and Duroc piglets during suckling and weaning periods

This study explored the developmental changes in small intestinal barrier function and the potential regulatory roles of intestinal microbiota and metabolites in different breeds of piglets during suckling and weaning periods. Taoyuan black (TB), Xiangcun black (XB), and Duroc (DR) piglets (10 litters per breed; half male and half female) were selected for sampling to evaluate the intestinal barrier-related indexes and intestinal microbiota and metabolites at 1, 10, 21 (weaned), and 24 (3 d after weaning) d old. The results showed that weaning led to severe shedding of small intestinal microvilli and sparse microvilli arrangement. D-lactate level in the ileum of TB and XB piglets during suckling and weaning periods was lower (P < 0.01) than that of DR piglets, as well as the ileal diamine oxidase level at 1 d old. The expression level of mucin 1 was higher (P < 0.05) in the ileum of TB and XB piglets than that of DR piglets, and it was the highest in the ileum of TB piglets at 21 d old. The expression levels of mucin 2 and mucin 13 were higher (P < 0.10) in TB and XB piglets than those of DR piglets at 21 d old, whereas mucin 2 and mucin 13 in the ileum of TB and XB piglets were higher (P < 0.05) than those of DR piglets at 24 d old. TB and XB piglets had a lower relative abundance of Escherichia_Shigella at 21 and 24 d old, but they had higher Streptococcus at 1 and 24 d old than DR piglets (P < 0.01). Differential metabolites between the three breeds of piglets were mainly related to oxidative phosphorylation, steroid biosynthesis, and bile acid synthesis. Collectively, these findings suggest that different pig breeds present differences in the development of the small intestinal barrier function. Compared with DR piglets, TB and XB piglets had higher intestinal permeability during the suckling period and a stronger intestinal mechanical barrier after weaning. Moreover, intestinal microbiota and metabolites are the key factors for developing small intestinal barrier functions in different breeds of piglets.

Gut microbiome signatures of extreme environment adaption in Tibetan pig

Tibetan pigs (TPs) can adapt to the extreme environments in the Tibetan plateau implicated by their self-genome signals, but little is known about roles of the gut microbiota in the host adaption. Here, we reconstructed 8210 metagenome-assembled genomes from TPs (n = 65) living in high-altitude and low-altitude captive pigs (87 from China-CPs and 200 from Europe-EPs) that were clustered into 1050 species-level genome bins (SGBs) at the threshold of 95% average nucleotide identity. 73.47% of SGBs represented new species. The gut microbial community structure analysis based on 1,048 SGBs showed that TPs was significantly different from low-altitude captive pigs. TP-associated SGBs enabled to digest multiple complex polysaccharides, including cellulose, hemicellulose, chitin and pectin. Especially, we found TPs showed the most common enrichment of phyla Fibrobacterota and Elusimicrobia, which were involved in the productions of short- and medium-chain fatty acids (acetic acid, butanoate and propanoate; octanomic, decanoic and dodecanoic acids), as well as in the biosynthesis of lactate, 20 essential amino acids, multiple B vitamins (B1, B2, B3, B5, B7 and B9) and cofactors. Unexpectedly, Fibrobacterota solely showed powerful metabolic capacity, including the synthesis of acetic acid, alanine, histidine, arginine, tryptophan, serine, threonine, valine, B2, B5, B9, heme and tetrahydrofolate. These metabolites might contribute to host adaptation to high-altitude, such as energy harvesting and resistance against hypoxia and ultraviolet radiation. This study provides insights into understanding the role of gut microbiome played in mammalian high-altitude adaptation and discovers some potential microbes as probiotics for improving animal health.

Effects of dietary supplementation with multispecies probiotics on intestinal epithelial development and growth performance of neonatal calves challenged with Escherichia coli K99

BACKGROUND

Probiotics exhibit antibiotic properties and are capable of treating certain bacterial infections, including diarrhea. Therefore, the aim of this study is to investigate the effects of dietary supplementation with multispecies probiotic (MSP) on diarrhea, average daily gain (ADG) and intestinal development of neonatal calves challenged with Escherichia coli K99.

RESULTS

Thirty-six neonatal Holstein calves were randomly assigned to three treatment groups. After E. coli K99 challenge, calves in the control (C) and MSP treatment groups had significantly higher ADG and feed efficiency, and significantly lower fecal scores than those of calves in the diarrhea (D) group. The mean time of diarrhea resolution was 4.5 and 3.1 days for calves in the D and MSP treatment groups, respectively. Furthermore, the structures of the various segments (duodenum, jejunum and ileum) of the small intestine of the calves, activities of several small intestinal enzymes, and expression of several energy metabolism-related genes in the small intestine segments were significantly affected by MSP treatments.

CONCLUSION

Dietary supplementation of MSP had a positive effect in treating calf diarrhea; it improved ADG and feed efficiency and promoted development of the small intestine. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Dietary Amylose-Amylopectin Ratio on Growth Performance and Intestinal Digestive and Absorptive Function in Weaned Piglet Response to Lipopolysaccharide

This study investigated the effects of diet with different amylose−amylopectin ratios (AAR) on the growth performance, intestinal morphology, digestive enzyme activities and mRNA expression of nutrients transporters in piglets with short-term lipopolysaccharide (LPS) intraperitoneal injections. Sixty 21 days-old piglets (Landrace × Yorkshire; 6.504 ± 0.079) were randomly assigned based on their body weight (BW) and litters of origins to five groups with experimental diets with an AAR of 0.00, 0.20, 0.40, 0.60, or 0.80 (namely, the 0.00, 0.20, 0.40, and 0.80 groups), respectively. Each treatment included 12 piglets (one piglet per pen). This experiment lasted for 28 days. On the 28th day, six piglets in each treatment were randomly selected for an LPS intraperitoneal injection (100 μg/kg BW), and other piglets were injected with normal saline. Twelve hours after LPS injection, all piglets were sacrificed to collect small intestinal mucosa for analysis. Although different AAR did not influence the final BW in piglets, the piglets in the 0.40 group represented the poorest feed-to-gain ratio (F/G) in the first, second and fourth week (p < 0.05) and the lowest average daily gain (ADG) in the fourth week (p < 0.05) compared with other groups. In terms of the small intestinal morphology, piglets in the 0.20 and 0.60 groups showed better ileal villous width (p < 0.05). Piglets in the 0.60 group presented greater activities of jejunal maltase, sucrase and alkaline phosphatase (p < 0.05) than those of 0.20 and 0.40. However, a low amylose diet increased the mRNA expression of jejunal glucose and amino acid transporters (p < 0.05). In addition, compared to saline injection, the LPS challenge significantly lessened jejunal digestive enzyme activities (p < 0.01) and, ileal villous width and downregulated the gene expression of glucose and amino acid transporters (p < 0.05) in piglets. Interestingly, certain diet -LPS interactions on duodenal VH/CD, jejunal maltase activity (p < 0.05) and the expression of glucose transporters (p < 0.05) were observed. Taken together, in terms of small intestinal digestion and absorption capacity, these results demonstrated that a diet with an AAR of 0.60 diets could improve the intestinal digestive and absorptive capability by affecting small intestinal morphology, digestive enzymes, and nutrients absorptions in piglets. In addition, the diets containing an AAR of 0.40−0.60 were more likely to resist the damage of LPS stress to intestinal morphology and nutrient absorption.

Distribution of free amino acids and mRNA expression of their corresponding transporters in the intestinal mucosa of goats feeding on a corn grain versus corn gluten diet

BACKGROUND

Intestinal amino acid (AA) chemosensing has been implicated in the regulation of AA absorption, nitrogen metabolism and hormone release, thereby playing an indispensable role in maintaining metabolic homeostasis in mammals. The objective of this experiment was to study the distribution of free AA and the expression of AA transporting related genes along the small and large intestines of Liuyang black goats, together with the effects of dietary corn grain replaced by dietary corn gluten feed (CGF).

RESULTS

The CGF replacement did not alter (P > 0.05) AA profiles and the expression of AA transporting related genes in the intestinal mucosa. Intriguingly, in terms of gut regions, the concentrations of aspartic acid and glutamic acid in the mucosa of ileum were remarkably less (P < 0.001) than those in the large intestine. Moreover, the concentrations of most cationic and neutral AAs shared the same distribution pattern, with the jejunum and ileum holding the greatest and least levels (P < 0.05), respectively. It was notable that the expression of both anionic and cationic AA transporters in the small intestine was exceedingly greater (P < 0.001) than those in the large intestine. As for transporters of neutral AA, system ASC, L, and A showed an extremely distinctive expression pattern.

CONCLUSION

The jejunum would be the primary site of transporting AA, while CGF substitution does not exert a disadvantageous influence on the AA chemosensing systems of the first-pass metabolism. © 2021 Society of Chemical Industry.

Effects of iron, vitamin A, and the interaction between the two nutrients on intestinal development and cell differentiation in piglets

This study aimed to investigate the effects of iron, vitamin A (VA) and their interaction on intestinal development and differentiation of cells in suckling piglets. Therefore, 32 Duroc × Landrace × Yorkshire 0-d-old newborn boars with similar body weights were randomly divided into four groups, with eight replicates in each group and one pig in each replicate. All the piglets were breastfed. In addition, the piglets were given normal saline (CON group) or ferrous sulfate (OAFe group) or VA (VA group) or ferrous sulfate and VA (OAFe + VA group) on the 2nd, 7th, 12th, and 17th day, respectively. The piglets were then slaughtered on the 21st day, and intestinal samples were collected. The results showed that: 1) iron (P < 0.001) significantly increased the length, weight, relative weight, and the length to weight ratio of the small intestine. On the other hand, VA had a significant effect on the weight to length ratio (P = 0.015) and relative weight (P < 0.001) of the small intestine; 2) with regard to intestinal morphology, supplementation with iron (P <0.05) had obvious effects on the villus height (VH), crypt depth (CD), villus width (VW), and surface area. Additionally, both VA and interaction of VA and iron increased the VH (P < 0.05) and surface area (P = 0.001). The results also showed that iron (P < 0.01) increased the number of crypt goblet cells, Ki67-positive cells, and endocrine cells. Moreover, both VA and the interaction between VA and iron increased the number of endocrine cells in the villi (P = 0.05); 3) With regard to the mRNA expression levels of stem cell differentiation marker genes, iron (P < 0.05) decreased the expression of trophinin 2 (Trop2), leucine-rich repeat containing G protein-coupled receptor 5 positive (Lgr5+), male-specific lethal 1(Msl1), BMI 1 proto-oncogene, polycomb ring finger (Bmi1), and achaete-scute family bHLH transcription factor 2 (Ascl2). On the other hand, VA increased the expression of Ascl2 (P = 0.001) although the interaction of VA and iron (P < 0.05) had an effect on the expression of secreted phosphoprotein 1 (Spp1) and Bmi1. In addition, VA decreased the gene or mRNA expression of aconitase 1 (Aco1; P < 0.001), transferrin receptor (TFRC; P = 0.001), and solute carrier family 11 member 2 (DMT1; P = 0.003) in the Iron Reactive Element/Iron Regulatory Protein (IRE/IRP) signaling pathway although iron and the interaction of VA and iron had no effect on the genes' expression. The results therefore showed that VA, iron, and their interaction can promote intestinal development and epithelial cell differentiation in piglets.

Nano chitosan-zinc complex improves the growth performance and antioxidant capacity of the small intestine in weaned piglets

The present study was conducted to test the hypothesis that dietary supplementation with a nano chitosan-zinc complex (CP-Zn, 100 mg/kg Zn) could alleviate weaning stress in piglets challenged with enterotoxigenic Escherichia coli K88 by improving growth performance and intestinal antioxidant capacity. The in vivo effects of CP-Zn on growth performance variables (including gastrointestinal digestion and absorption functions and the levels of key proteins related to muscle growth) and the antioxidant capacity of the small intestine (SI) were evaluated in seventy-two weaned piglets. The porcine jejunal epithelial cell line IPEC-J2 was used to further investigate the antioxidant mechanism of CP-Zn in vitro. The results showed that CP-Zn supplementation increased the jejunal villus height and decreased the diarrhoea rate in weaned piglets. CP-Zn supplementation also improved growth performance (average daily gain and average daily feed intake), increased the activity of carbohydrate digestion-related enzymes (amylase, maltase, sucrase and lactase) and the mRNA expression levels of nutrient transporters (Na+-dependent glucose transporter 1, glucose transporter type 2, peptide transporter 1 and excitatory amino acid carrier 1) in the jejunum and up-regulated the expression levels of mammalian target of rapamycin (mTOR) pathway-related proteins (insulin receptor substrate 1, phospho-mTOR and phospho-p70S6K) in muscle. In addition, CP-Zn supplementation increased glutathione content, enhanced total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-px) activity, and reduced malondialdehyde (MDA) content in the jejunum. Furthermore, CP-Zn decreased the content of MDA and reactive oxygen species, enhanced the activity of T-SOD and GSH-px and up-regulated the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway-related proteins (Nrf2, NAD(P)H:quinone oxidoreductase 1 and haeme oxygenase 1) in lipopolysaccharide-stimulated IPEC-J2 cells. Collectively, these findings indicate that CP-Zn supplementation can improve growth performance and the antioxidant capacity of the SI in piglets, thus alleviating weaning stress.

Herbal Extract Mixture Modulates Intestinal Antioxidative Capacity and Microbiota in Weaning Piglets

Recently, herbal extracts have been applied in multiple aspects, such as medicine and animal feed. Different compositions of herbal extract mixture (HEM) have various components and diverse functions. This study aimed to evaluate the effects of HEM (Lonicera japonica, Astragalus membranaceus, Eucommia folium, and Codonopsis pilosula) on intestinal antioxidant capacity and colonic microbiota in weaned pigs. A total of 18 piglets [Duroc × (Landrace × Yorkshire)] with the initial body weight of 5.99 ± 0.13 kg (weaned at 21 days) were randomly divided into two groups (n = 9): the control group (CON, basal diet) and the HEM treatment group (HEM, 1,000 mg/kg HEM + basal diet). The experiment period lasted for 14 days. Our results showed that dietary supplementation with HEM modulated the antioxidant capacity through decreasing the activity of superoxide dismutase (SOD) in the ileum and glutathione peroxidase (GSH-PX) in the serum, and decreasing the mRNA expression of Kelch like-ECH-associated protein 1 (Keap1) in the jejunum and the protein level of Keap1 in the ileum. Moreover, the HEM group modified the composition of colonic microbiota with affecting relative abundances of the Firmicutes and Bacteroidetes at the phylum level. Taken together, supplementation of HEM can regulate the antioxidant capacity and modify the composition of colonic bacteria in weaning piglets. This study provides new insights into the combination effects of herbal extracts on weaning piglets.

Invited Review: Maintain or Improve Piglet Gut Health around Weanling: The Fundamental Effects of Dietary Amino Acids

Gut health has significant implications for swine nutrient utilization and overall health. The basic gut morphology and its luminal microbiota play determinant roles for maintaining gut health and functions. Amino acids (AA), a group of essential nutrients for pigs, are not only obligatory for maintaining gut mucosal mass and integrity, but also for supporting the growth of luminal microbiota. This review summarized the up-to-date knowledge concerning the effects of dietary AA supplementation on the gut health of weanling piglets. For instance, threonine, arginine, glutamine, methionine and cysteine are beneficial to gut mucosal immunity and barrier function. Glutamine, arginine, threonine, methionine and cysteine can also assist with relieving the post-weaning stress of young piglets by improving gut immunological functions, antioxidant capacity, and/or anti-inflammatory ability. Glutamine, glutamate, glycine and cysteine can assist to reconstruct the gut structure after its damage and reverse its dysfunction. Furthermore, methionine, lysine, threonine, and glutamate play key roles in affecting bacteria growth in the lumen. Overall, the previous studies with different AA showed both similar and different effects on the gut health, but how to take advantages of all these effects for field application is not clear. It is uncertain whether these AA effects are synergetic or antagonistic. The interactions between the effects of non-nutrient feed additives and the fundamental effects of AA warrant further investigation. Considering the global push to minimize the antibiotics and ZnO usage in swine production, a primary effort at present may be made to explore the specific effects of individual AA, and then the concert effects of multiple AA, on the profile and functions of gut microbiota in young pigs.

Imbalanced dietary methionine-to-sulfur amino acid ratio can affect amino acid profiles, antioxidant capacity, and intestinal morphology of piglets

Animal protein sources such as fishmeal and plasma powder are excellent and indispensable sources of energy, amino acids, and minerals in animal production. Amino acid imbalance, especially methionine-to-sulfur amino acid (Met:SAA) ratio, caused by an imbalance of animal protein meal leads to growth restriction. This study was conducted to evaluate the effects of imbalanced Met:SAA ratio supplementation of different animal protein source diets on growth performance, plasma amino acid profiles, antioxidant capacity and intestinal morphology in a piglet model. Twenty-four weaned piglets (castrated males; BW = 10.46 ± 0.34 kg), assigned randomly into 3 groups (8 piglets/group), were fed for 28 d. Three experimental diets of equal energy and crude protein levels were as follows: 1) a corn-soybean basal diet with a Met:SAA ratio at 0.51 (BD); 2) a plasma powder diet with a low Met:SAA ratio at 0.41 (L-MR); 3) a fishmeal diet with a high Met:SAA ratio at 0.61 (H-MR). Results revealed that compared to BD, L-MR significantly decreased (P < 0.05) the activities of plasma total antioxidant capacity and glutathione peroxidase, plasma amino acid profiles, and significantly reduced (P < 0.05) villus height and crypt depth in the duodenum and jejunum. Additionally, L-MR significantly reduced (P < 0.05) the mRNA expression level of solute carrier family 7 member 9 (SlC7A9) in the ileum, and significantly increased (P < 0.05) mRNA expression levels of zonula occludens-1 (ZO-1) in the duodenum, and Claudin-1, ZO-1, sodium-coupled neutral amino acid transporters 2 (SNAT2) and SlC7A7 in the jejunum. H-MR significantly increased (P < 0.05) plasma SAA levels, and significantly reduced (P < 0.05) average daily feed intake, villus height, and villus height-to-crypt depth (VH:CD) ratio in the ileum compared to BD. In conclusion, L-MR may result in oxidative stress and villous atrophy but proves beneficial in improving intestinal barrier function and the activity of amino acid transporters for compensatory growth. H-MR may impair intestinal growth and development for weaned piglets. The research provides a guidance on the adequate Met:SAA ratio (0.51) supplementation in diet structure for weaned piglets.

Effect of antibiotic-free, low-protein diets with specific amino acid compositions on growth and intestinal flora in weaned pigs

This study investigated the effects of modulation of the amino acid profile on growth performance and gut health in weaned pigs fed an antibiotic-free, low-protein diet. In experiment 1, 5 treatments were included: a control diet with antibiotics; a low-protein diet with antibiotics; a low-protein diet without antibiotics (LP); a LP diet with 10% more dietary essential amino acids (LP110); and an LP110 diet with 12% more dietary Met + Cys, Thr and Trp. The intestinal digestive enzyme activity and morphology were improved with the increase in dietary essential amino acid levels, while the growth performance was decreased, indicating that the dietary amino acid level was too high. In experiment 2, all 5 treatments of experiment 1 were included, plus a LP diet with 5% more dietary essential amino acids (LP105) and an LP105 diet with 6% more dietary Met + Cys, Thr and Trp. The LP105 treatment showed optimal feed efficiency, a reduced plasma endotoxin concentration, and an increased fecal lactate concentration and increased abundances of Prevotellaceae and Roseburia bacteria. Our results demonstrate that the optimal amino acid profile in an antibiotic-free, low-protein diet can efficiently improve growth performance and gut health and modulate the fecal microbial structure in weaned pigs.

Effects of dietary supplementation with herbal extract mixture on growth performance, organ weight and intestinal morphology in weaning piglets

BACKGROUND

Many countries are increasingly prohibiting the addition of antibiotics in livestock diets. Therefore, herb extracts have gradually drawn attention to substitute antibiotics. Our present study aimed to determine the effects of herbal extract mixture (HEM) in dietary on growth performance, organ weight, intestinal morphology and intestinal nutrient transporters in weaned pigs.

METHODS

27 piglets (Duroc × [Landrace × Yorkshire]; Body Weight (BW) = 5.99 ± 0.13 kg) were weaned at day 21 and randomly divided into three groups (n = 9 piglets/group). All piglets received a basal diet containing similar amounts of nutrients for 14 days. The three groups were the control (no additive), the antibiotics (375 mg/kg chlortetracycline, 20%, 500 mg/kg enramycin, 4%, 1,500 mg/kg oxytetracycline calcium, 50%) and the HEM group (1000 mg/kg extract mixture of golden-and-silver honeysuckle, huangqi, duzhong leaves and dangshen). After 14 d of treatment, we collected tissue samples to measure organ weight, intestinal parameters, intestinal morphology, digestive enzyme activities and intestinal mRNA expression of nutrient transporters.

RESULTS

The HEM group had no effects on growth performance and organ weight of weaned pigs. But compared with the control group, both HEM and antibiotics improved intestinal morphology, and HEM elevated the expression of nutrient transporters in ileum (SLC6A9, SLC15A1, and SLC5A1). HEM significantly decreased the activities of maltase in ileum and the ratio of small intestinal weight to BW than control group.

CONCLUSIONS

These results indicate benefit effects of the supplementation of HEM in diet, including modulating intestinal morphology and increasing the mRNA expression of nutrients transporters. These findings suggest that HEM provides novel insights into a variety of herbal extract mixtures to replace antibiotics in animal production.

Postnatal growth retardation is associated with intestinal mucosa mitochondrial dysfunction and aberrant energy status in piglets

Individuals with postnatal growth retardation (PGR) are prone to developing chronic disease. Abnormal development in small intestine is casually implicated in impaired growth performance. However, the exact mechanism is still unknown. In this present study, PGR piglets (aged 42 days) were employed as a good model to analyse changes in nutrient absorption and energy metabolism in the intestinal mucosa. The results showed lower serum concentrations of free amino acids, and lipid metabolites in PGR piglets, which were in accordance with the down‐regulated mRNA expressions involved in fatty acid and amino acid transporters in the jejunal and ileal mucosa. The decreased activities of digestive enzymes and the marked swelling in mitochondria were also observed in the PGR piglets. In addition, it was found that lower ATP production, higher AMP/ATP ratio, deteriorated mitochondrial complex III and ATP synthase, and decreased manganese superoxide dismutase activity in the intestinal mucosa of PGR piglets. Furthermore, altered gene expression involved in energy metabolism, accompanied by decreases in the protein abundance of SIRT1, PGC‐1α and PPARγ, as well as phosphorylations of AMPKα, mTOR, P70S6K and 4E‐BP1 were observed in intestinal mucosa of PGR piglets. In conclusion, decreased capability of nutrient absorption, mitochondrial dysfunction, and aberrant energy status in the jejunal and ileal mucosa may contribute to PGR piglets.

Changes in cecal morphology, cell proliferation, antioxidant enzyme, volatile fatty acids, lipopolysaccharide, and cytokines in piglets during the postweaning period

Weaning stresses often induce markedly structural and functional changes in the small intestine. However, little data are available on the changes of the morphology, function, and health in the cecum of piglets post-weaning. This study was conducted to measure the effects of weaning on the cecum in piglets. Forty piglets were weaned at 21 d and samples were collected at different time points (days 0, 1, 3, 7, and 14) post-weaning. The crypt depth, crypt width, and total epithelial cell numbers increased on days 7 and 14, compared with days 0, 1, and 3 (P < 0.001). The value of Ki67/total epithelial cells was highest on day 0 compared with all other days (P < 0.05). Besides, a higher concentration of malondialdehyde was observed on day 3 (P < 0.001). The activity of CuZn-superoxide dismutase (P < 0.05) enhanced from day 0 to 1 and the activity of catalase increased from day 1 to 3 (P < 0.001). In addition, days 3, 7, and 14 had greater acetic, propanoic, and butyric acid contents than on day 1 (P < 0.001). The pH and monocarboxylate transporter 1 (MCT1) expression increased from day 0 to 1 and from day 3 to 7 and decreased between days 1 and 3 (P < 0.001). The mRNA expression of solute carrier family 9 member A3 (SLC9A3) decreased on day 1 compared to all other postweaning days (P < 0.05). The abundance of toll-like receptor 4 (TLR4) and interferon-γ (IFN-γ) mRNA expression increased (P < 0.05) during the first 24 h after weaning. The concentration of lipopolysaccharide increased from day 3 to 7, then decreased on day 14 (P < 0.05). The mRNA expression of tumor necrosis factor-α (TNF-α) enhanced from day 7 to 14 (P < 0.05). The abundance of phosphorylated mammalian target of rapamycin protein was lower on day 14 than day 0 (P < 0.05). Taken together, these results show that weaning in piglets influences intestinal morphology, function, and health in the cecum.

Effects of vitamin B6 on the growth performance, intestinal morphology, and gene expression in weaned piglets that are fed a low-protein diet1

Vitamin B6 (VB6), which is an essential functional substance for biosome, plays an irreplaceable role in animal health. However, there are few studies that focus on the correlation between VB6 and intestinal health in weaned piglets. This study was conducted to investigate the effects of VB6 on the growth performance, intestinal morphology, and inflammatory cytokines and amino acid (AA) transporters mRNA expression in weaned piglets that are fed a low crude-protein (CP, 18%) diet. Eighteen crossbred piglets with initial body weights of 7.03 ± 0.17 kg (means ± SEM), weaned at 21-d age, were randomly assigned three diets with 0, 4, and 7 mg/kg VB6 supplementation, respectively. The experimental period lasted 14 days. Our results showed that there were no significant differences in growth performance, diarrhea rate, and biochemical parameters among the three treatments. In the jejunum, dietary VB6 supplementation did not affect the morphology and positive Ki67 counts. Dietary supplementation with 4 mg/kg VB6 decreased the mRNA expression of COX-2, IL-10, and TGF-β (P < 0.05). Dietary supplementation with 7 mg/kg VB6 increased the mRNA expression of SLC7A1, SLC7A6, SLC16A14, and SLC38A5 (P < 0.05) and 4 or 7 mg/kg VB6 decreased SLC36A1 mRNA expression (P < 0.05). In the ileum, VB6 supplementation did not affect positive Ki67 counts but significantly decreased villus area (P < 0.05) and tended to decrease villus height (P = 0.093). Dietary supplementation with 4 mg/kg VB6 had significantly increased the mRNA expression of IL-1β, TNF-α, COX-2, IL-10, and TGF-β (P < 0.05). Dietary supplementation with 4 or 7 mg/kg VB6 had significantly decreased SLC6A20, SLC7A1, SLC7A6, SLC16A14, and SLC38A5 mRNA expression (P < 0.05). These findings suggest that dietary supplementation of VB6 mainly down-regulated inflammatory cytokines and up-regulated AA transporters mRNA expression in jejunum, while up-regulated (4 mg/kg) inflammatory cytokines and down-regulated AA transporters mRNA expression in ileum, which may provide a reference for the intestinal development of weaned piglets that are fed a low-CP diet.

Effects of dietary microencapsulated tannic acid supplementation on the growth performance, intestinal morphology, and intestinal microbiota in weaning piglets

Antibiotics are commonly overused to reduce weaning stress that leads to economic loss in swine production. As potential substitutes of antibiotics, plant extracts have attracted the attention of researchers. However, one of the plant extracts, tannic acid (TA), has an adverse effect on the growth performance, palatability, and intestinal absorption in weaning piglets when used at a large amount. Thus, this study aimed to investigate the effects of a proper dose of microencapsulated TA on the growth performance, organ and intestinal development, intestinal morphology, intestinal nutrient transporters, and colonic microbiota in weaning piglets. Forty-five Duroc × [Landrace × Yorkshire] (initial body weight = 5.99 ± 0.13 kg, weaned days = 21 d) piglets were randomly divided into five treatment groups (n = 9) and raised in 14 d. The piglets in the control group were raised on a basal diet; the piglets in the antibiotic test group were raised on a basal diet with three antibiotics (375 mg/kg Chlortetracycline 20%, 500 mg/kg Enramycin 4%, 1,500 mg/kg Oxytetracycline calcium 20%); and the other three groups were raised on a basal diet with three doses of microencapsulated TA (TA1, 500 mg/kg; TA2, 1,000 mg/kg; TA3, 1,500 mg/kg). All the piglets were raised in the same environment and given the same amount of nutrients for 2 wk. The results showed that both TA1 and TA2 groups had no adverse effect on the growth performance, organ weight and intestinal growth, and the pH value of gastrointestinal content. TA2 treatment improved the duodenal morphology (P < 0.05), increased the gene expression level of solute carrier family 6, member 19 and solute carrier family 15, member 1 (P < 0.05) in the ileum, and modulated the colonic bacteria composition (P < 0.05), but inhibited the activity of maltase in the ileum (P < 0.05) and the jejunal gene expression level of solute carrier family 5, member 1 (P < 0.05). In conclusion, our study suggests that a dosage between 500 and 1,000 mg/kg of microencapsulated TA is safe to be included in the swine diet and that 1,000 mg/kg of microencapsulated TA has beneficial effects on intestinal morphology, intestinal nutrient transporter, and intestinal microbiota in weaning piglets. These findings provide new insights into suitable alternatives to antibiotics for improving growth performance and colonic microbiota.

Effects of vitamin B6 on growth, diarrhea rate, intestinal morphology, function, and inflammatory factors expression in a high-protein diet fed to weaned piglets1

Vitamin B6 (VB6) is an important coenzyme factor which participates in many metabolic reactions, especially amino acid metabolism. There are few reports on how VB6 mediates weaned piglet intestinal health. This study purposed to investigate dietary VB6 effects on growth, diarrhea rates, and intestinal morphology and function in weaned piglets fed a high-crude protein (22% CP) diet. Eighteen 21-d-old weaned [(Yorkshire × Landrace) × Duroc] piglets with body weights of 7.03 ± 0.15 (means ± SEM) kg were randomly assigned into 3 VB6-containing dietary treatments. Vitamin B6 content was: 0, 4, and 7 mg/kg, respectively. The feeding period lasted 14 d. The results showed that no significant difference existed for the growth performance. The 7 mg/kg VB6 group had a tendency to decrease diarrhea rate (P = 0.065). Blood biochemical parameters analysis demonstrated that total protein, cholesterol, and high-density lipoprotein significantly increased in the 7 mg/kg VB6 group (P < 0.05). In the jejunum, no significant differences were detected for villus height, villus width, crypt depth, villus height and crypt depth ratios, and positive Ki67 counts and the mRNA expression of inflammatory cytokines. Vitamin B6 significantly increased the mRNA expression of SLC6A19 and SLC6A20 (P < 0.05) and decreased the mRNA expression of SLC36A1 (P < 0.05). In the ileum, VB6 significantly increased villus height and villus width (P < 0.05) while decreased positive Ki67 cell counts for 7 mg/kg VB6 group (P < 0.05). Vitamin B6 had significantly increased the mRNA expression of interleukin-1β, tumor necrosis factor-α,cyclo-oxygen-ase-2, and transforming growth factor-β (P < 0.05). Vitamin B6 also had significantly increased mRNA expression of SLC6A19, SLC7A6, SLC7A7, and SLC36A1 (P < 0.05). These findings suggest that dietary supplementation with VB6 may affect the intestinal morphology and absorption and metabolism of protein in weaned piglets fed a high-protein diet by altering the expression of intestinal inflammatory cytokines and amino acid transporters.

Dietary xylo-oligosaccharide improves intestinal functions in weaned piglets

This study aimed at investigating the effects of dietary xylo-oligosaccharide (XOS) on intestinal functions (i.e., intestinal morphology, tight junctions, gut microbiota and metabolism) and growth performance in weaned piglets. 19 weaned piglets were randomly divided into two groups (n = 9/10): a control group (basic diet) and a XOS treated group in which piglets were fed 0.01% XOS for 28 days. Growth performance, blood cells and biochemical parameters, serum cytokines, intestinal morphology, tight junctions, gut microbiota, and the metabolic profiles of the gut digesta were analyzed. The results showed that dietary supplementation with XOS had little effects on growth performance, blood cells and biochemical parameters, and intestinal morphology. However, the inflammatory status and intestinal barrier were improved in XOS-fed piglets evidenced by the reduction of IFN-γ and upregulation of ZO-1. Microbiota analysis showed that XOS enhanced α-diversity and affected the relative abundances of Lactobacillus, Streptococcus, and Turicibacter at the genus level. The alterations in the microbiota might be further involved in carbohydrate metabolism, cell motility, cellular processes and signaling, lipid metabolism, and metabolism of other amino acids by functional prediction. A metabolomics study identified three differentiated metabolites, including coenzyme Q6, zizyphine A, and pentadecanal, which might be produced by the microbiota and further affect host metabolism. In conclusion, dietary XOS improved the inflammatory status, gut barrier, and microbiota communities, which might be used as a potential feed additive to prevent gut dysfunction caused by weaning in the pig industry.

Dietary sulfur amino acids affect jejunal cell proliferation and functions by affecting antioxidant capacity, Wnt/β-catenin, and the mechanistic target of rapamycin signaling pathways in weaning piglets

Intestinal epithelial cells undergo rapid renewal along the crypt-villus axis (CVA), which ensures intestinal functions. Weaning stress differentially effects intestinal epithelial cell metabolism and physiological states along the CVA. Sulfur amino acids (SAA) play a key role in intestinal epithelial cell functioning. This study evaluated the effects of SAA dietary supplementation on weaning pig jejunal epithelial cells along the CVA. Sixteen Duroc × Landrace × Yorkshire piglets (6.16 ± 0.22 kg BW) were weaned at 21 d of age and were blocked by BW and gender and the randomly assigned to 1 of 2 groups fed diets consisting of low (0.53%) or high (0.85%) levels of SAA for a 7-d period. All piglets were euthanized for tissue sampling on day 7 postweaning. Jejunal epithelial cells were isolated along the CVA to yield 3 "cell fractions" (upper villus, middle villus, and crypt cells). The number of proliferating cells per crypt of piglets fed the high SAA diet was lower (P < 0.05) than that for low SAA diet. High SAA diet piglets tended to have decreased (P = 0.059) sucrase activities compared low SAA diet piglets. A high SAA diet increased (P < 0.05) total antioxidant capacity, catalase, and superoxide dismutase activities compared with a low SAA diet. mRNA expression levels of claudin-1, Slc5a1, and Slc7a9 in high SAA diet piglets were lower (P < 0.05) than for low SAA diet piglets. There were no interactions between dietary SAA and cell sections along the CVA for enzyme activities and mRNA expression in any of the weaned piglets. Protein amounts and phosphorylation levels related to Wnt/β-catenin and mechanistic targeting of rapamycin (mTOR) signaling pathways were affected by SAA in weaning piglets. These findings indicate that dietary SAA affects jejunal cell proliferation and functions in weaning piglets. There appears to be no interactions between dietary SAA and cell sections along the CVA. The effects of SAA may be partly through affecting antioxidant capacity, and Wnt/β-catenin and mTOR signaling pathway.

Nutritional Intervention for the Intestinal Development and Health of Weaned Pigs

Weaning imposes simultaneous stress, resulting in reduced feed intake, and growth rate, and increased morbidity and mortality of weaned pigs. Weaning impairs the intestinal integrity, disturbs digestive and absorptive capacity, and increases the intestinal oxidative stress, and susceptibility of diseases in piglets. The improvement of intestinal development and health is critically important for enhancing nutrient digestibility capacity and disease resistance of weaned pigs, therefore, increasing their survival rate at this most vulnerable stage, and overall productive performance during later stages. A healthy gut may include but not limited several important features: a healthy proliferation of intestinal epithelial cells, an integrated gut barrier function, a preferable or balanced gut microbiota, and a well-developed intestinal mucosa immunity. Burgeoning evidence suggested nutritional intervention are one of promising measures to enhance intestinal health of weaned pigs, although the exact protective mechanisms may vary and are still not completely understood. Previous research indicated that functional amino acids, such as arginine, cysteine, glutamine, or glutamate, may enhance intestinal mucosa immunity (i.e., increased sIgA secretion), reduce oxidative damage, stimulate proliferation of enterocytes, and enhance gut barrier function (i.e., enhanced expression of tight junction protein) of weaned pigs. A number of feed additives are marketed to assist in boosting intestinal immunity and regulating gut microbiota, therefore, reducing the negative impacts of weaning, and other environmental challenges on piglets. The promising results have been demonstrated in antimicrobial peptides, clays, direct-fed microbials, micro-minerals, milk components, oligosaccharides, organic acids, phytochemicals, and many other feed additives. This review summarizes our current understanding of nutritional intervention on intestinal health and development of weaned pigs and the importance of mechanistic studies focusing on this research area.

Physiological Effects of Dietary Amino Acids on Gut Health and Functions of Swine

Gut health has significant implications for swine overall health status and nutrient utilization, due to its various functions including digestion and absorption of nutrients, secretion of mucins and immunoglobulins, and selective barrier protection against harmful antigens and pathogens. Both the basic anatomical structure of the gut (such as epithelial cells) and its luminal microbiota play important roles for maintaining gut health and functions. The interactions between epithelial cells and luminal microbiota have significant impact on host nutrition and health through the metabolism of dietary components. Amino acids, which are major nutrients for pigs, are not only obligatory for maintaining the intestinal mucosal mass and integrity, but also for supporting the growth of microorganisms in the gut. Dietary amino acids are the major fuel of the small intestinal mucosa. Particularly, glutamate, glutamine, and aspartate are the major oxidative fuel of the intestine. Emerging evidence shows that arginine activates the mTOR signaling pathway in the small intestine. Utilization of glycine by the small intestinal mucosa to synthesize glutathione is a very important physiological pathway, and the role of glycine as a powerful cytoprotectant has also been recognized. The major end products of methionine and cysteine metabolism are glutathione, homocysteine and taurine, which play important roles in the intestinal immune and anti-oxidative responses. Threonine is highly utilized by the gut and is particularly important for mucin synthesis and maintenance of gut barrier integrity. Moreover, either a deficiency or an excess of dietary threonine can reduce the synthesis of intestinal mucosal proteins and mucins in young pigs. Various new functions of amino acids on gut health and functions have been discovered in recent years. Thus, this review is to provide some up-to-date knowledge for industry application of dietary amino acids in order to enhance swine gut health and functions, and also it is to provide a comprehensive reference for further scientific research in this regard.