Dietary fiber sources and non-starch polysaccharide-degrading enzymes modify mucin expression and the immune profile of the swine ileum

Fecal microbial and metabolic characteristics of swine from birth to market

Introduction

Recently, the research on pig intestinal microbiota has become a hot topic in the field of animal husbandry. There are few articles describing the dynamic changes of porcine fecal microbiota and metabolites at different time points from birth to market.

Methods

In the present study, 381 fecal samples were collected from 633 commercial pigs at 7 time points, including the 1st day, the 10th day, the 25th day, the 45th day, the 70th day, the 120th day, and the 180th day after the birth of swine, were used for microbiome analysis by Illumina MiSeq sequencing methods while 131 fecal samples from 3 time points, the 10th day, the 25th day, and 70th day after birth, were used for metabolome analysis by LC-MS methods.

Results

For the microbiome analysis, the fecal microbial richness increased over time from day 1 to 180 and the β-diversity of fecal microbiota was separated significantly at different time points. Firmicutes were the main phyla from day 10 to 180, followed by Bacteroides. The abundance of Lactobacillus increased significantly on day 120 compared with the previous 4 time points. From day 120 to day 180, the main porcine fecal microbes were Lactobacillus, Clostridium_sensu_stricto_1, Terrisporobacter and Streptococcus. Clostridium_sensu_stricto_1 and Terrisporobacter increased over time, while Lactobacillus, Escherichia-Shigella, Lachnoclostridium decreased with the time according to the heatmap, which showed the increase or decrease in microbial abundance over time. For the metabolome analysis, the PLS-DA plot could clearly distinguish porcine fecal metabolites on day 10, 25, and 70. The most different metabolic pathways of the 3 time points were Tryptophan metabolism, Sphingolipid signaling pathway, Protein digestion and absorption. Some metabolites increased significantly over time, such as Sucrose, L-Arginine, Indole, 2,3-Pyridinedicarboxylic acid and so on, while D-Maltose, L-2-Aminoadipic acid, 2,6-diaminohexanoic acid, L-Proline were opposite. The correlation between fecal metabolites and microbiota revealed that the microbes with an increasing trend were positively correlated with the metabolites affecting the tryptophan metabolic pathway from the overall trend, while the microbes with a decreasing trend were opposite. In addition, the microbes with an increasing trend were negatively correlated with the metabolites affecting the lysine pathway.

Discussion

In conclusion, this study elucidated the dynamic changes of porcine fecal microbiota and metabolites at different stages from birth to market, which may provide a reference for a comprehensive understanding of the intestinal health status of pigs at different growth stages.

β-mannanase supplemented in diets saved 85 to 100 kcal of metabolizable energy/kg, supporting growth performance and improving nutrient digestibility in grower pigs

The effects of β-mannanase supplementation in metabolizable energy (ME)-reduced diets containing xylanase-phytase were investigated on growth performance, fecal score, ultra-sounded backfat thickness and loin depth, blood profile, apparent total tract digestibility (ATTD), digesta passage rate, and fecal microbiome in grower pigs (n = 40, 26.09 ± 0.96 kg) randomly assigned within 4 treatments: a control diet containing isolated phytase and xylanase valued at 40 kcal of ME/kg (CD0), CD0 + β-mannanase (0.3 g/kg valued at 30 kcal of ME/kg) (CD70), CD0 + β-mannanase (0.3 g/kg valued at 45 kcal of ME/kg) (CD85), and CD0 + β-mannanase (0.3 g/kg valued at 60 kcal of ME/kg) (CD100). Growth performance was not affected in pigs fed ME-reduced diets containing β-mannanase. Pigs with CD100 had lower serum IL-1β concentration, and higher IL-10 was observed in pigs on CD0 than those fed β-mannanase. Coefficients of ATTD, and ATTD of DM and CP were higher in animals fed CD85 or CD100. Pigs with CD85 had higher alpha diversity richness but lower Firmicutes:Bacteroidota ratio. Acidaminococcaceae and Ruminococcaceae were more abundant in pigs fed CD0, but lower for Christensenellaceae NSJ-63 and NSJ-63 sp014384805. Pigs in CD85 showed higher Bacteroidaceae and Prevotella abundance, and lower for Streptococcaceae and Streptococcus. In conclusion, supplementation of β-mannanase in diets containing xylanase-phytase saved 85 to 100 kcal of ME/kg by supporting growth performance and improving nutrient digestibility in grower pigs.

Acute infection with Brachyspira hyodysenteriae affects mucin expression, glycosylation, and fecal MUC5AC

Introduction

Infection with strongly β-hemolytic strains of Brachyspira hyodysenteriae leads to swine dysentery (SD), a production-limiting disease that causes mucohemorrhagic diarrhea and typhlocolitis in pigs. This pathogen has strong chemotactic activity toward mucin, and infected pigs often have a disorganized mucus layer and marked de novo expression of MUC5AC, which is not constitutively expressed in the colon. It has been shown that fucose is chemoattractant for B. hyodysenteriae, and a highly fermentable fiber diet can mitigate and delay the onset of SD.

Methods

We used lectins targeting sialic acids in α-2,6 or α-2,3 linkages, N-acetylglucosamine (GlcNAc), α-linked L-fucose, and an immunohistochemical stain targeting N-glycolylneuraminic acid (NeuGc) to investigate the local expression of these mucin glycans in colonic tissues of pigs with acute SD. We used a commercial enzyme-linked immunosorbent assay (ELISA) to quantify fecal MUC5AC in infected pigs and assess its potential as a diagnostic monitoring tool and RNA in situ hybridization to detect IL-17A in the colonic mucosa.

Results

Colonic mucin glycosylation during SD has an overall increase in fucose, a spatially different distribution of GlcNAc with more expression within the crypt lumens of the upper colonic mucosa, and decreased expression or a decreased trend of sialic acids in α-2,6 or α-2,3 linkages, and NeuGc compared to the controls. The degree of increased fucosylation was less in the colonic mucosa of pigs with SD and fed the highly fermentable fiber diet. There was a significant increase in MUC5AC in fecal and colonic samples of pigs with SD at the endpoint compared to the controls, but the predictive value for disease progression was limited.

Discussion

Fucosylation and the impact of dietary fiber may play important roles in the pathogenesis of SD. The lack of predictive value for fecal MUC5AC quantification by ELISA is possibly due to the presence of other non-colonic sources of MUC5AC in the feces. The moderate correlation between IL-17A, neutrophils and MUC5AC confirms its immunoregulatory and mucin stimulatory role. Our study characterizes local alteration of mucin glycosylation in the colonic mucosa of pigs with SD after B. hyodysenteriae infection and may provide insight into host-pathogen interaction.

Dietary zinc restriction affects the expression of genes related to immunity and stress response in the small intestine of pigs

Zinc (Zn) is an essential mineral and its deficiency manifests in non-specific clinical signs that require long time to develop. The response of swine intestine to Zn restriction was evaluated to identify early changes that can be indicative of Zn deficiency. Twenty-seven pigs (body weight = 77⋅5 ± 2⋅5 kg) were assigned to one of three diets: diet without added Zn (Zn-restricted diet, ZnR), and ZnR-supplemented with either 50 (Zn50) or 100 mg of Zn/kg of diet (Zn100) of Zn supplied by ZnCl₂. After 32 d consuming the diets, serum Zn concentration in ZnR pigs was below the range of 0⋅59-1⋅37 μg/ml considered sufficient, thereby confirming subclinical Zn deficiency. Pigs showed no obvious health or growth changes. RNA-seq analysis followed by qPCR showed decreased expression of metallothionein-1 (MT1) (P < 0⋅05) and increased expression of Zn transporter ZIP4 (P < 0⋅05) in jejunum and ileum of ZnR pigs compared with Zn-supplemented pigs. Ingenuity pathway analysis revealed that Zn50 and Zn100 induced changes in genes related to nucleotide excision repair and integrin signalling pathways. The top gene network in the ZnR group compared with Zn100 was related to lipid and drug metabolism; and compared with Zn50, was related to cellular proliferation, assembly and organisation. Dietary Zn concentrations resulted in differences in genes related to immune pathways. Our analysis showed that small intestine presents changes associated with Zn deficiency after 32 d of Zn restriction, suggesting that the intestine could be a sentinel organ for Zn deficiency.

Identification of Independent and Shared Metabolic Responses to High-Fiber and Antibiotic Treatments in Fecal Metabolome of Grow-Finish Pigs

Feeding high-fiber (HF) coproducts to grow–finish pigs as a cost-saving practice could compromise growth performance, while the inclusion of antibiotic growth promoters (AGPs) may improve it. The hindgut is a shared site of actions between fiber and AGPs. However, whether the metabolic interactions between them could occur in the digestive tract of pigs and then become detectable in feces have not been well-examined. In this study, wheat middling (WM), a HF coproduct, and bacitracin, a peptide antibiotic (AB), were fed to 128 grow–finish pigs for 98 days following a 2 × 2 factorial design, including antibiotic-free (AF) + low fiber (LF); AF + HF; AB + LF, and AB + HF, for growth and metabolic responses. The growth performance of the pigs was compromised by HF feedings but not by AB. A metabolomic analysis of fecal samples collected on day 28 of feeding showed that WM elicited comprehensive metabolic changes, especially in amino acids, fatty acids, and their microbial metabolites, while bacitracin caused selective metabolic changes, including in secondary bile acids. Limited metabolic interactions occurred between fiber and AB treatments. Moreover, the correlations between individual fecal metabolites and growth support the usage of fecal metabolome as a source of biomarkers for monitoring and predicting the metabolic performance of grow–finish pigs.

Farm and Companion Animal Organoid Models in Translational Research: A Powerful Tool to Bridge the Gap Between Mice and Humans

Animal organoid models derived from farm and companion animals have great potential to contribute to human health as a One Health initiative, which recognize a close inter-relationship among humans, animals and their shared environment and adopt multi-and trans-disciplinary approaches to optimize health outcomes. With recent advances in organoid technology, studies on farm and companion animal organoids have gained more attention in various fields including veterinary medicine, translational medicine and biomedical research. Not only is this because three-dimensional organoids possess unique characteristics from traditional two-dimensional cell cultures including their self-organizing and self-renewing properties and high structural and functional similarities to the originating tissue, but also because relative to conventional genetically modified or artificially induced murine models, companion animal organoids can provide an excellent model for spontaneously occurring diseases which resemble human diseases. These features of companion animal organoids offer a paradigm-shifting approach in biomedical research and improve translatability of in vitro studies to subsequent in vivo studies with spontaneously diseased animals while reducing the use of conventional animal models prior to human clinical trials. Farm animal organoids also could play an important role in investigations of the pathophysiology of zoonotic and reproductive diseases by contributing to public health and improving agricultural production. Here, we discuss a brief history of organoids and the most recent updates on farm and companion animal organoids, followed by discussion on their potential in public health, food security, and comparative medicine as One Health initiatives. We highlight recent evolution in the culturing of organoids and their integration with organ-on-a-chip systems to overcome current limitations in in vitro studies. We envision multidisciplinary work integrating organoid culture and organ-on-a-chip technology can contribute to improving both human and animal health.

Decreased nutrient digestibility due to viscosity is independent of the amount of dietary fibre fed to growing pigs

Fibre content and its effect on chyme viscosity are associated with changes in the digestive system of humans and pigs. It is unclear if fibre content and viscosity affect digestive function independently or interactively. We evaluated apparent ileal digestibility (AID) of nutrients and intestinal function in thirty-six ileal-cannulated barrows fed for 29 d either maize-soyabean meal (MSBM) or high-fibre MSBM + 30 % distillers dried grains with solubles (MSBM + DDGS) modified to three levels of viscosity by adding 5 % non-viscous cellulose (CEL), 6·5 % medium-viscous carboxymethylcellulose (MCMC) or 6·5 % high-viscous CMC (HCMC). Digesta were collected on days 27 and 28 and intestinal samples on day 29. Feeding CMC, regardless of fibre content, increased viscosity of whole digesta (P = 0·003) and digesta supernatant (P < 0·0001) compared with CEL. Feeding MSBM + DDGS or CMC decreased AID of DM (P = 0·003; P < 0·0001) and crude protein (P = 0·02; P < 0·0001) compared with MSBM or CEL. Feeding CMC regardless of fibre content increased jejunal crypt depth (P = 0·02) and ileal goblet cell area (P = 0·004) compared with CEL. Adding DDGS or CMC did not affect villus height and gene expression of jejunal monosaccharide and amino acid transporters. Feeding HCMC, regardless of fibre content, elevated amylase activity by 46 and 50 % in jejunal (P = 0·03) and ileal digesta (P = 0·01) compared with CEL. In summary, diets with increased viscosity decreased nutrient digestibility and induced intestinal changes that were independent of the amount of fibre fed.

The Probiotic Properties of Lactic Acid Bacteria and Their Applications in Animal Husbandry

The intestinal tract of animals is a complex ecosystem in which nutrients, microbiota and host cells interact extensively. Probiotics can be considered as part of the natural microbiota of the gut and are involved in improving homeostasis. Lactic acid bacteria (LAB) is a general term for a class of non-spore forming, gram-positive bacteria whose main product of fermented sugar is lactic acid. LAB are considered to be a type of probiotic due to their health-promoting effects on the host, and are very effective in the treatment of human and animal diseases. LAB have been widely used as a class of microbial agents in the field of livestock and poultry breeding. They are also considered to be the best substitutes for antibiotics to improve animal health. Here, we review the biological functions, probiotic characteristics and applications of LAB in livestock and poultry breeding. This review is designed to provide a theoretical base for the in-depth exploration and promotion of LAB use in animal diets.

Comparative Effects of Compound Enzyme and Antibiotics on Growth Performance, Nutrient Digestibility, Blood Biochemical Index, and Intestinal Health in Weaned Pigs

This experiment aims to explore the effects of compound enzyme preparation substituting chlortetracycline on growth performance, serum immune markers, and antioxidant capacity and intestinal health in weaned piglets. A total of twenty-four 28-day-old “Duroc × Landrace × Yorkshire” weaned piglets with an average initial weight of 7.25 ± 0.25 kg were randomly divided into three groups according to their body weight, with eight replicates in each group and one pig in each replicate. The three dietary treatments were basal diet (CON), basal diet + 1,000 mg/kg compound enzyme preparation (cellulase 4,000 IU/g, α-amylase 1,000 IU/g, β-glucanase 150 IU/g, and neutral protease 3,000 IU/g, CE), and basal diet + 75 mg/kg chlortetracycline (CTC). The animal experiment lasted for 28 days and was divided into two stages: the early stage (0–14 days) and the late stage (15–28 days). The results showed that (1) compared with the CON, the CE and CTC significantly increased the ADG of weaned piglets during the early and whole period of experiment (p < 0.05), decreased the F:G in the whole experiment period (p < 0.05), and diarrhea rate in the early stage (p < 0.01). (2) Compared with the CON, the apparent total tract digestibility of ADF and NDF was significantly increased in pigs fed the CE diet in the early and late stages of experiment (p < 0.05) with no significant difference compared with the CTC. (3) Compared with the CON, the concentrations of serum IgA and SOD in weaned piglets were significantly increased in the CE group in the early stage of the experiment (p < 0.05). (4) Compared with the CON group, the acetic acid, propionic acid, and total VFA contents in cecum and colon segments were elevated in the CE group (p < 0.05) with no significant difference compared with the CTC. (5) Compared with the CON group, the villus height of duodenum and jejunum and the ratio of villus height to recess depth of ileum were increased in the CE and CTC group (p < 0.05). (6) Compared with the CON group, the abundance of Lactobacillus significantly increased (p < 0.01) while the abundance of Escherichia coli decreased in the CE group and CTC group (p < 0.01). In conclusion, CE preparation instead of CTC can significantly improve the nutrient digestibility, the immunity, antioxidant capacity, and intestinal health of pigs, which may contribute to the improved growth performance of piglets.

Porcine small intestinal organoids as a model to explore ETEC-host interactions in the gut

Small intestinal organoids, or enteroids, represent a valuable model to study host–pathogen interactions at the intestinal epithelial surface. Much research has been done on murine and human enteroids, however only a handful studies evaluated the development of enteroids in other species. Porcine enteroid cultures have been described, but little is known about their functional responses to specific pathogens or their associated virulence factors. Here, we report that porcine enteroids respond in a similar manner as in vivo gut tissues to enterotoxins derived from enterotoxigenic Escherichia coli, an enteric pathogen causing postweaning diarrhoea in piglets. Upon enterotoxin stimulation, these enteroids not only display a dysregulated electrolyte and water balance as shown by their swelling, but also secrete inflammation markers. Porcine enteroids grown as a 2D-monolayer supported the adhesion of an F4⁺ ETEC strain. Hence, these enteroids closely mimic in vivo intestinal epithelial responses to gut pathogens and are a promising model to study host–pathogen interactions in the pig gut. Insights obtained with this model might accelerate the design of veterinary therapeutics aimed at improving gut health.

Effect of dietary crude protein level on growth performance, blood characteristics, and indicators of intestinal health in weanling pigs

An experiment was conducted to test the hypothesis that reducing crude protein (CP) in starter diets for pigs reduces post-weaning diarrhea and improves intestinal health. In total, 180 weanling pigs were allotted to 3 diets containing 22, 19, or 16% CP. Fecal scores were visually assessed every other day. Blood samples were collected from 1 pig per pen on days 1, 6, 13, 20, and 27, and 1 pig per pen was euthanized on day 12. Results indicated that reducing dietary CP reduced (P < 0.01) overall average daily gain, gain to feed ratio, final body weight, and fecal scores of pigs. Pigs fed the 16% CP diet had reduced (P < 0.01) serum albumin compared with pigs fed other diets. Blood urea nitrogen, haptoglobin, interleukin-1β, and interleukin-6 concentrations in serum were greatest (P < 0.01) on day 13, whereas tumor necrosis factor-α and interleukin-10 concentrations were greatest (P < 0.01) on day 6. Villus height in the jejunum increased (P < 0.05) and crypt depth in the ileum was reduced (P < 0.01) if the 19% CP diet was fed to pigs compared with the 22% CP diet. A reduction (P < 0.05) in mRNA abundance of interferon-γ, chemokine ligand 10, occludin, trefoil factor-2, trefoil factor-3, and mucin 2 was observed when pigs were fed diets with 16% CP. In conclusion, reducing CP in diets for weanling pigs reduces fecal score and expression of genes associated with inflammation.

Measures Matter-Determining the True Nutri-Physiological Value of Feed Ingredients for Swine

Many types of feed ingredients are used to provide energy and nutrients to meet the nutritional requirements of swine. However, the analytical methods and measures used to determine the true nutritional and physiological ("nutri-physiological") value of feed ingredients affect the accuracy of predicting and achieving desired animal responses. Some chemical characteristics of feed ingredients are detrimental to pig health and performance, while functional components in other ingredients provide beneficial health effects beyond their nutritional value when included in complete swine diets. Traditional analytical procedures and measures are useful for determining energy and nutrient digestibility of feed ingredients, but do not adequately assess their true physiological or biological value. Prediction equations, along with ex vivo and in vitro methods, provide some benefits for assessing the nutri-physiological value of feed ingredients compared with in vivo determinations, but they also have some limitations. Determining the digestion kinetics of the different chemical components of feed ingredients, understanding how circadian rhythms affect feeding behavior and the gastrointestinal microbiome of pigs, and accounting for the functional properties of many feed ingredients in diet formulation are the emerging innovations that will facilitate improvements in precision swine nutrition and environmental sustainability in global pork-production systems.

Organoids: a promising new in vitro platform in livestock and veterinary research

Organoids are self-organizing, self-renewing three-dimensional cellular structures that resemble organs in structure and function. They can be derived from adult stem cells, embryonic stem cells, or induced pluripotent stem cells. They contain most of the relevant cell types with a topology and cell-to-cell interactions resembling that of the in vivo tissue. The widespread and increasing adoption of organoid-based technologies in human biomedical research is testament to their enormous potential in basic, translational- and applied-research. In a similar fashion there appear to be ample possibilities for research applications of organoids from livestock and companion animals. Furthermore, organoids as in vitro models offer a great possibility to reduce the use of experimental animals. Here, we provide an overview of studies on organoids in livestock and companion animal species, with focus on the methods developed for organoids from a variety of tissues/organs from various animal species and on the applications in veterinary research. Current limitations, and ongoing research to address these limitations, are discussed. Further, we elaborate on a number of fields of research in animal nutrition, host-microbe interactions, animal breeding and genomics, and animal biotechnology, in which organoids may have great potential as an in vitro research tool.

Alteration of Colonic Mucin Composition and Cytokine Expression in Acute Swine Dysentery

Swine dysentery (SD) is an enteric disease associated with strongly β-hemolytic Brachyspira spp. that cause mucohemorrhagic diarrhea primarily in grower-finisher pigs. We characterized alteration of colonic mucin composition and local cytokine expression in the colon of pigs with acute SD after B. hyodysenteriae (Bhyo) infection and fed either a diet containing 30% distillers dried grains with solubles (DDGS) or a control diet. Colonic tissue samples from 9 noninoculated pigs (Control, N = 4; DDGS, N = 5) and 10 inoculated pigs experiencing acute SD (Bhyo, N = 4; Bhyo-DDGS, N = 6) were evaluated. At the apex of the spiral colon, histochemical staining with high-iron diamine-Alcian blue revealed increased sialomucin (P = .008) and decreased sulfomucin (P = .027) in Bhyo pigs relative to controls, with a dietary effect for sulfomucin. Noninoculated pigs fed DDGS had greater expression of sulfomucin (P = .002) compared to pigs fed the control diet. Immunohistochemically, there was de novo expression of mucin 5AC (MUC5AC) in the Bhyo group while mucin 2 (MUC2) expression was not significantly different between groups. RNA in situ hybridization to detect the pro-inflammatory cytokine IL-1β often showed increased expression in the Bhyo group although without statistical significance, and this was not correlated with MUC5AC or MUC2 expression, suggesting IL-1β is not a major regulator of their secretion in acute SD. Expression of the anti-inflammatory cytokine TGF-β1 was significantly suppressed in the Bhyo group compared to controls (P = .005). This study reveals mucin and cytokine alterations in the colon of pigs with experimentally induced SD and related dietary effects of DDGS.

Intestinal organoids in farm animals

In livestock species, the monolayer of epithelial cells covering the digestive mucosa plays an essential role for nutrition and gut barrier function. However, research on farm animal intestinal epithelium has been hampered by the lack of appropriate in vitro models. Over the past decade, methods to culture livestock intestinal organoids have been developed in pig, bovine, rabbit, horse, sheep and chicken. Gut organoids from farm animals are obtained by seeding tissue-derived intestinal epithelial stem cells in a 3-dimensional culture environment reproducing in vitro the stem cell niche. These organoids can be generated rapidly within days and are formed by a monolayer of polarized epithelial cells containing the diverse differentiated epithelial progeny, recapitulating the original structure and function of the native epithelium. The phenotype of intestinal organoids is stable in long-term culture and reflects characteristics of the digestive segment of origin. Farm animal intestinal organoids can be amplified in vitro, cryopreserved and used for multiple experiments, allowing an efficient reduction of the use of live animals for experimentation. Most of the studies using livestock intestinal organoids were used to investigate host-microbe interactions at the epithelial surface, mainly focused on enteric infections with viruses, bacteria or parasites. Numerous other applications of farm animal intestinal organoids include studies on nutrient absorption, genome editing and bioactive compounds screening relevant for agricultural, veterinary and biomedical sciences. Further improvements of the methods used to culture intestinal organoids from farm animals are required to replicate more closely the intestinal tissue complexity, including the presence of non-epithelial cell types and of the gut microbiota. Harmonization of the methods used to culture livestock intestinal organoids will also be required to increase the reproducibility of the results obtained in these models. In this review, we summarize the methods used to generate and cryopreserve intestinal organoids in farm animals, present their phenotypes and discuss current and future applications of this innovative culture system of the digestive epithelium.

Growth performance, nutrient digestibility, and fecal microbial composition of weaned pigs fed multi-enzyme supplemented diets

A study determined the effects of supplementing corn-based diets for weaned pigs with multi-enzymes on growth performance, apparent total tract digestibility (ATTD) of nutrients, fecal score, and fecal microbial composition. A total of 132 pigs (initial body weight = 7.23 kg) that had been weaned at 21 d of age and fed a drug-free nursery diet for 7 d were housed in 33 pens of 4 barrows or gilts, blocked by body weight and gender, and fed 3 experimental diets at 11 pens per diet. The diets were corn-based diet without or with multi-enzyme A or B. Multi-enzyme A supplied 4,000 U of xylanase, 150 U of β-glucanase, 3,500 U of protease, and 1,500 U of amylase per kilogram of diet. Multi-enzyme B was the same as multi-enzyme A except that it supplied amylase at 150 U/kg, and that its source of amylase was different from that of multi-enzyme A. All diets contained phytase at 1,000 U/kg. The diets were fed for 35 d in 2 phases; phase 1 for the first 14 d and phase 2 for the last 21 d of the trial. Fecal score was determined daily during the first 7 d of the trial. Fecal samples were collected from rectum of 1 pig per pen on days 2, 7, 14, and 35 of the trial for determining bacterial composition. Also, fresh fecal samples were collected from each pen on days 41 and 42 to determine ATTD of nutrients. Multi-enzyme B increased (P < 0.05) average daily gain (ADG) for phases 1 and 2. For the overall study period, multi-enzyme B increased (P < 0.05) ADG from 262 to 313 g, and average daily feed intake (ADFI) from 419 to 504 g. Multi-enzyme A increased (P < 0.05) overall ADG from 262 to 290 g, but did not affect ADFI. Multi-enzyme A or B did not affect ATTD of gross energy, but increased (P < 0.05) the ATTD of ether extract from 30% to 36% or 37%, respectively. Multi-enzyme A did not affect fecal score; however, multi-enzyme B tended to decrease (P = 0.09) fecal score, implying that it tended to decrease diarrhea. Firmicutes were the most abundant phylum of fecal bacteria (its relative abundance ranged from 58% to 72%). Bacteroidetes and Actinobacteria were the 2nd and 3rd most abundant phyla of fecal bacteria. Neither multi-enzyme affected fecal bacterial composition. In conclusion, the addition of multi-enzyme A or B to phytase-supplemented corn-based diet for weaned pigs can improve their growth performance and fat digestibility. However, multi-enzyme B was more effective than multi-enzyme A in terms of improving the growth performance of weaned pigs fed corn-based diet.

Swine gut microbiota and its interaction with host nutrient metabolism

Gut microbiota is generally recognized to play a crucial role in maintaining host health and metabolism. The correlation among gut microbiota, glycolipid metabolism, and metabolic diseases has been well reviewed in humans. However, the interplay between gut microbiota and host metabolism in swine remains incompletely understood. Given the limitation in conducting human experiments and the high similarity between swine and humans in terms of anatomy, physiology, polyphagy, habits, and metabolism and in terms of the composition of gut microbiota, there is a pressing need to summarize the knowledge gained regarding swine gut microbiota, its interplay with host metabolism, and the underlying mechanisms. This review aimed to outline the bidirectional regulation between gut microbiota and nutrient metabolism in swine and to emphasize the action mechanisms underlying the complex microbiome-host crosstalk via the gut microbiota-gut-brain axis. Moreover, it highlights the new advances in knowledge of the diurnal rhythmicity of gut microbiota. A better understanding of these aspects can not only shed light on healthy and efficient pork production but also promote our knowledge on the associations between gut microbiota and the microbiome-host crosstalk mechanism. More importantly, knowledge on microbiota, host health and metabolism facilitates the development of a precise intervention therapy targeting the gut microbiota.

Effect of phytase on nutrient digestibility and expression of intestinal tight junction and nutrient transporter genes in pigs

The study was conducted to determine the effects of high levels of phytase on growth performance, nutrient digestibility, phytate breakdown, and expression of mucosal tight junction and nutrient transporter genes in weanling pigs. A total of 128 barrows were penned in groups of four and used in a randomized completely block design and assigned to four treatments for a 28-d study. A two-phase feeding was implemented (phase 1: day 1 to 14; phase 2: day 15 to 28). The diets differed in dietary calcium (Ca) and phosphorus (P) levels (positive control [PC]: 8.1 to 7.1 g/kg Ca and 6.5 to 6.8 g/kg P; negative control [NC]: 6.6 to 5.5 g/kg Ca and 5.6 to 5.3 g/kg P) from phase 1 to phase 2, respectively. NC diets were supplemented with phytase at 0 (NC), 1,500 (NC + 1,500), or 3,000 (NC + 3,000) phytase units (FTU)/kg. Blood was collected after fasting (day 27) or feeding (day 28) for the measurement of plasma inositol concentrations. On day 28, two pigs per pen were euthanized. Duodenal-jejunal and ileal digesta samples and feces were collected to determine inositol phosphates (InsP3-6) concentrations. Phytase supplementation increased the body weight on days 14 and 28 (P < 0.05). Average daily gain and feed efficiency compared with NC were increased by phytase with the majority of its effect in phase 1 (P < 0.05). The apparent ileal digestibility and apparent total tract digestibility of P were increased in piglets fed phytase-supplemented diets (P < 0.01) compared with NC piglets. Disappearance of InsP6 and total InsP3-6 up to the duodenum-jejunum, ileum, and in feces was increased by both phytase application rates (P < 0.01). Plasma concentrations of myo-inositol were higher (P < 0.001) in the phytase-supplemented diets than PC and NC diets, irrespective of whether pigs were fed or fasted. Expression of claudin 3 was higher in pigs fed both phytase-supplemented diets in the duodenum and jejunum compared with PC and NC. Mucin 2 expression was lower in the ileum of NC + 3,000 fed piglets compared with PC (P < 0.05), whereas expression of GLUT2 (solute carrier family 2-facilitated glucose transporter member 2) was increased (P < 0.05) by the NC + 3,000 treatment in all sections. In summary, high phytase supplementation increased the growth performance of nursery pigs. The increased expression of GLUT2 by phytase may indicate an upregulation of glucose absorption from the intestine by phytase.

Analysis of Gastrointestinal Responses Revealed Both Shared and Specific Targets of Zinc Oxide and Carbadox in Weaned Pigs

Antibiotics and pharmacological zinc supplementation were commonly used as growth promoters for several decades in the swine industry before being limited because of public health and environmental concerns. Further, the physiological and metabolic responses associated with their growth promotion effects are unclear. To characterize these responses induced by pharmacological zinc supplementation (2500 mg/kg) and carbadox (55 mg/kg), 192 post-weaning pigs were fed basal and test diets for 43 days. Compared with basal, pharmacological zinc and carbadox independently improved growth performance. Pharmacological zinc increased gastric mucosa thickness compared with basal zinc, while carbadox increased intestinal villus:crypt ratio compared with non-carbadox. Pharmacological zinc and carbadox independently reduced interleukin (IL)-1β concentration compared with basal zinc and non-carbadox. Pharmacological zinc increased IL-1RA:IL-1 ratio by 42% compared with basal zinc, while carbadox tended to increase the IL-10 and IL10:IL-12 ratio compared with non-carbadox. Carbadox increased fecal concentrations of histidine and lysine compared with non-carbadox. The independent effect of pharmacological zinc and carbadox on morphology and nutrient metabolism, and their shared effect on immunity may contribute to the additive effect on growth promotion. These results further confirmed the concept that growth promotion is multifactorial intervention. Therefore, elucidating growth-promoting effects and searching for alternatives should include wide-spectrum evaluation.

Pectin and inulin stimulated the mucus formation at a similar level: An omics-based comparative analysis

Mucin 2 (MUC2) is the skeleton of colonic mucus that comprises the physical intestinal barrier. Different dietary polysaccharides may affect colonic mucus at different extents. The effect of pectin on MUC2 production is contradictory. To investigate whether and how pectin affected hosts' colonic mucus, the amount of MUC2 in colon, the cecal, mucosal microbiota, and metabolites profiles were analyzed and compared with inulin. The results showed pectin stimulated the production of MUC2 at a similar level to inulin. Both interventions increased the abundance of cecal Lachnospira and Christensenellaceae_R-7_group, and enhanced the production of specific metabolites including soyasapogenol B 24-O-b-d-glucoside, lucyoside Q, trans-EKODE-(E)-Ib, and 1,26-dicaffeoylhexacosanediol. Additionally, pectin increased the relative abundance (RA) of cecal Lactobacillus, and induced less RA of potentially harmful bacteria such as Helicobacter in mucosal microbiota than inulin. In conclusion, we first reported that pectin and inulin stimulated the mucus formation at a similar level. Two genera of cecal bacteria and four metabolites may play an important role in enhancing the production of MUC2. Moreover, the MUC2 production may be unrelated to several traditional health-beneficial bacteria; pectin possibly performed as good as or better than the inulin in rats' gut.

Evaluation of swine enteroids as in vitro models for Lawsonia intracellularis infection1,2

The enteric pathogen Lawsonia intracellularis is one of the main causes of diarrhea and compromised weight gain in pigs worldwide. Traditional cell-line cultures have been used to study L. intracellularis pathogenesis. However, these systems fail to reproduce the epithelial changes observed in the intestines of L. intracellularis-infected pigs, specifically, the changes in intestinal cell constitution and gene expression. A more physiologically accurate and state-of-the-art model is provided by swine enteroids derived from stem cell-containing crypts from healthy pigs. The objective of this study was to verify the feasibility of two-dimensional swine enteroids as in vitro models for L. intracellularis infection. We established both three- and two-dimensional swine enteroid cultures derived from intestinal crypts. The two-dimensional swine enteroids were infected by L. intracellularis in four independent experiments. Enteroid-infected samples were collected 3 and 7 d postinfection for analysis using real-time quantitative PCR and L. intracellularis immunohistochemistry. In this study, we show that L. intracellularis is capable of infecting and replicating intracellularly in two-dimensional swine enteroids derived from ileum.

Interleukin-4 suppresses the proliferation and alters the gene expression in enteroids

Interleukin (IL)-4 is known as a cytokine mainly involved in allergy and inflammation, but recent studies have suggested that IL-4 plays a part in the differentiation process of various cells. Since the effect of IL-4 on intestinal epithelial cells, particularly cryptic cells including stem cells, is poorly understood, we investigated IL-4-induced changes in intestinal epithelial cells using mouse jejunal organoids called enteroids. IL-4 treatment decreased cell proliferation, the expression of the stem cell markers leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) and olfactomedin 4 (Olfm4), and Lgr5-positive cells in enteroids. Among the differentiation markers, IL-4 significantly decreased the gene expression levels of the Paneth cell markers lysozyme 1 (Lyz1) and regenerating islet-derived protein 3 gamma (Reg3γ). A fluorescent immunostaining showed that IL-4 attenuated the emission and fluorescence intensity derived from lysozyme, which is enriched in Paneth cells. These results suggest that functional changes in Paneth cells caused by IL-4 may contribute to the reduction in Lgr5-positive cells and proliferative activity. IL-4 may affects gut function by altering the proliferation and the gene expression in enteroids.

TGF-β1 promoted the infection of bovine mammary epithelial cells by Staphylococcus aureus through increasing expression of cells' fibronectin and integrin β1

Mastitis is a disease that affects dairy cattle and causes a decline in milk quality as well as economic loss worldwide. TGF-β1 levels are usually increased during mastitis; however, it is unknown whether TGF-β1 is involved in bovine mastitis. Therefore, this study evaluated the effects of TGF-β1 on the susceptibility of bovine mammary epithelial cells (BMECs) to Staphylococcus aureus (S. aureus). The results revealed that S. aureus adhesion to and invasion of BMECs was significantly increased after cells were treated with TGF-β1. Adhesion of S. aureus to BMECs was increased dramatically by upregulation of fibronectin (Fn) and integrin β1 (ITGB1), while the increase in the susceptibility of BMECs to S. aureus was blocked by specific antibodies against either Fn or ITGB1. These results indicated that adhesion and invasion were increased by TGF-β1-induced upregulation of both Fn and ITGB1. Furthermore, TGF-β1 treatment prior to S. aureus infection significantly increased S. aureus colonization as well as Fn and ITGB1 expression in the mammary glands of mice. These results suggest that TGF-β1 promoted the expression of Fn and ITGB1 on the surface of BMECs and contributed to mammary gland infection in vitro and in vivo. The results of this study imply that Fn and ITGB1 may be useful therapeutic targets for the treatment of mastitis in dairy cows.

Evaluation of mouse enteroids as a model for Lawsonia intracellularis infection

Lawsonia intracellularis, an obligate intracellular bacterium, is an important enteric pathogen in pig herds and horse farms worldwide. The hallmark feature of L. intracellularis infection is the proliferation of epithelial cells in intestinal crypts. A major limitation to the study of L. intracellularis infection is the lack of an in vitro model that reproduces the changes observed in proliferative enteropathy. Here we investigated the suitability of mouse enteroids as a model to study L. intracellularis infection. Mouse enteroids were microinjected with L. intracellularis, filter-sterilized L. intracellularis culture supernatant, or sterile cell culture media (DMEM). L. intracellularis antigen was detected in mouse enteroids by immunohistochemistry and was located mostly in the basal region of the epithelium. There was no differential growth of enteroids among treatment groups, and cellular proliferation was not increased in L. intracellularis-infected enteroids in relation to non-infected enteroids based on immunofluorescence staining. L. intracellularis infection did not induce changes in gene expression of Ki-67 (proliferation marker), Sox9 (marker for transit amplifying cells) and Muc2 (marker for goblet cells). These results indicate that although L. intracellularis antigen is detectable in mouse enteroids, indicating susceptibility to infection, mouse enteroids fail to replicate the cellular proliferation and gene expression changes observed in proliferative enteropathy. Nevertheless, we have successfully demonstrated that mouse enteroids can be used to model days-long intracellular pathogen infection, serving as potential models for the study of other pathogens of interest in veterinary medicine.