Calf intestinal mucin: isolation, partial characterization, and measurement in ileal digesta with an enzyme-linked immunosorbent assay

Host innate immune responses and microbiome profile of neonatal calves challenged with Cryptosporidium parvum and the effect of bovine colostrum supplementation

Introduction

Calves are highly susceptible to gastrointestinal infection with Cryptosporidium parvum (C. parvum), which can result in watery diarrhea and eventually death or impaired development. With little to no effective therapeutics, understanding the host's microbiota and pathogen interaction at the mucosal immune system has been critical to identify and test novel control strategies.

Methods

Herein, we used an experimental model of C. parvum challenge in neonatal calves to describe the clinical signs and histological and proteomic profiling of the mucosal innate immunity and microbiota shifts by metagenomics in the ileum and colon during cryptosporidiosis. Also, we investigated the impact of supplemental colostrum feeding on C. parvum infection.

Results

We showed that C. parvum challenged calves experienced clinical signs including pyrexia and diarrhea 5 days post challenge. These calves showed ulcerative neutrophil ileitis with a proteomic signature driven by inflammatory effectors, including reactive oxygen species and myeloperoxidases. Colitis was also noticed with an aggravated mucin barrier depletion and incompletely filled goblet cells. The C. parvum challenged calves also displayed a pronounced dysbiosis with a high prevalence of Clostridium species (spp.) and number of exotoxins, adherence factors, and secretion systems related to Clostridium spp. and other enteropathogens, including Campylobacter spp., Escherichia sp., Shigella spp., and Listeria spp. Daily supplementation with a high-quality bovine colostrum product mitigated some of the clinical signs and modulated the gut immune response and concomitant microbiota to a pattern more similar to that of healthy unchallenged calves.

Discussion

C. parvum infection in neonatal calves provoked severe diarrheic neutrophilic enterocolitis, perhaps augmented due to the lack of fully developed innate gut defenses. Colostrum supplementation showed limited effect mitigating diarrhea but demonstrated some clinical alleviation and specific modulatory influence on host gut immune responses and concomitant microbiota.

From Static to Dynamic: A Review on the Role of Mucus Heterogeneity in Particle and Microbial Transport

Mucus layers (McLs) are on the front line of the human defense system that protect us from foreign abiotic/biotic particles (e.g., airborne virus SARS-CoV-2) and lubricates our organs. Recently, the impact of McLs on human health (e.g., nutrient absorption and drug delivery) and diseases (e.g., infections and cancers) has been studied extensively, yet their mechanisms are still not fully understood due to their high variety among organs and individuals. We characterize these variances as the heterogeneity of McLs, which lies in the thickness, composition, and physiology, making the systematic research on the roles of McLs in human health and diseases very challenging. To advance mucosal organoids and develop effective drug delivery systems, a comprehensive understanding of McLs' heterogeneity and how it impacts mucus physiology is urgently needed. When the role of airway mucus in the penetration and transmission of coronavirus (CoV) is considered, this understanding may also enable a better explanation and prediction of the CoV's behavior. Hence, in this Review, we summarize the variances of McLs among organs, health conditions, and experimental settings as well as recent advances in experimental measurements, data analysis, and model development for simulations.

Modulation of Mucin Secretion in the Gut of Young Pigs by Dietary Threonine and Non-Essential Amino Acid Levels

Simple Summary

The mucus layer is an important part of the system protecting the gut against injuries and bacterial infections. The main components of mucus responsible for its properties are mucins. They are large glycoproteins with a protein core rich in threonine (Thr) and many sugar side chains that differ in structure and affect mucin functions. Diet composition affects the amount of secreted mucins and their quality. Therefore, the aim of the study was to determine the effect of Thr and wheat gluten (WG) protein, added as a source of non-essential amino acids, on the content of tissue and luminal mucins in different parts of the intestine of young pigs. Results showed that tissue and luminal mucin content was only affected by WG levels in the duodenum and middle jejunum, and in the proximal colon, respectively. The effect of WG on luminal mucin content in the proximal colon depended on the analytical method applied.

Abstract

The aim of the study was to determine the effect of threonine (Thr) and non-essential amino acid (NEAA) levels on mucin secretion and sugar composition of digesta and crude mucin preparations analyzed in different segments of the gut in young pigs. A two-factorial experiment was conducted on 72 pigs using the following factors: Thr level (5.1, 5.7, 6.3 and 6.9 g standardized ileal digestible(SID) Thr/kg) and wheat gluten (WG) level used as a source of NEAA (20.4, 40.4 and 60.4 g WG protein in WG20, WG40 and WG60 diets, respectively). Mucin content was affected only by WG level. Tissue mucin content in the duodenum was higher in WG60 pigs than in WG20 and WG40 pigs, whereas in the middle jejunum was higher in WG40 and WG60 pigs than in WG20 pigs. In contrast, luminal crude mucin content in the proximal colon was lower in WG60 pigs compared to WG40 pigs. The lowest and highest Thr levels reduced arabinose and xylose contents and increased glucose content in ileal digesta. The highest WG level reduced arabinose and xylose contents and increased glucose content in ileal digesta. The lowest WG level increased mannose content in ileal digesta. WG60 level decreased the content of arabinose and galactose compared to lower WG levels in colonic digesta. Arabinose content was higher, while glucose and galactose contents were lower in crude mucin preparations isolated from colonic digesta in pigs fed diets containing the highest Thr level. The content of tissue mucin was higher in the ileum and proximal colon and lower in the duodenum than in the middle jejunum, whereas luminal mucin content was lower in the proximal colon than in the ileum. Ileal digesta contained less arabinose and glucose and more galactose as compared to colonic digesta. In conclusion, no effect of dietary Thr levels on mucin secretion in the gut of young pigs was found. Wheat gluten added to the diet with adequate Thr content positively affected mucin secretion only in the duodenum and middle jejunum.

Purified mucins in drug delivery research

One of the main challenges in the field of drug delivery remains the development of strategies to efficiently transport pharmaceuticals across mucus barriers, which regulate the passage and retention of molecules and particles in all luminal spaces of the body. A thorough understanding of the molecular mechanisms, which govern such selective permeability, is key for achieving efficient translocation of drugs and drug carriers. For this purpose, model systems based on purified mucins can contribute valuable information. In this review, we summarize advances that were made in the field of drug delivery research with such mucin-based model systems: First, we give an overview of mucin purification procedures and discuss the suitability of model systems reconstituted from purified mucins to mimic native mucus. Then, we summarize techniques to study mucin binding. Finally, we highlight approaches that made use of mucins as building blocks for drug delivery platforms or employ mucins as active compounds.

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 2. Inositol phosphate esters hydrolysis, intestinal permeability, hematology, jejunal gene expression and intestinal morphology

This study investigated the hypothesis that feeding broilers over-processed meat and bone meal (MBM) would impair gut health in the absence of phytase and in turn, affect inositol phosphate (inositol x-phosphate, IPx: IP3, IP4, IP5 and IP6) ester hydrolysis, intestinal permeability, hematology, jejunal gene expression and intestinal morphology during necrotic enteritis (NE). Ross 308 male broilers (n = 768) were assigned to one of 8 dietary treatments in a 2 × 2 × 2 factorial arrangement, with 6 replicate pens per diet and 16 birds per pen in a completely randomized design. Factors were: NE challenge (no or yes), phytase level (500 or 5,000 FTU/kg) and MBM processing (as-received or over-processed). For the NE challenge, half of the birds were challenged with field strains of Eimeria spp. on d 9 and 10⁸ CFU/mL of Clostridium perfringens strain EHE-NE18 on d 14 and 15. A 3-way challenge, phytase and MBM processing interaction was detected for IP5 (P < 0.05) and IP6 (P < 0.05) levels in the ileum. Birds fed low phytase had increased IP5 and IP6 in unchallenged birds only when diets contained over-processed MBM. Challenge with NE increased intestinal permeability as measured by serum fluorescein isothiocyanate dextran (FITC-d; P < 0.001), increased white blood cells (WBC; P < 0.001), decreased mean corpuscular volume (MCV; P < 0.001) and mean corpuscular hemoglobin (MCH; P < 0.05), and decreased crypt-to-villi ratio (P < 0.05). The over-processed MBM reduced the villi-to-crypt ratio (P < 0.05). A 3-way challenge × phytase × MBM processing interaction was detected for mucin 2 (MUC-2) expression (P < 0.05) where only in unchallenged birds fed over-processed MBM did high phytase reduce MUC-2 expression. A lower expression of aminopeptidase N (APN; P < 0.001) and vitamin D receptor (VDR; P < 0.001) were recorded in NE challenged birds. In conclusion, NE has a negative impact on the gut and hematology of broilers, but its effect on phytate hydrolysis is minimal.

Technical note: Evaluation of 3 methods to determine mucin protein concentration in ileal digesta of young preweaning calves

The use of alternative sources of protein to substitute for milk proteins in milk replacers (MR) can increase the synthesis of endogenous proteins and therefore alter ileal or total-tract digestibility calculations. Mucin is the main component of gastrointestinal mucus and represents the greatest contribution to total endogenous protein. Mucin is difficult to isolate and has not been extensively studied in dairy calves. We explored 3 different procedures to analyze and estimate mucin protein (MUP) in ileal digesta of young dairy calves. Ileal digesta samples were collected from nine 30-d-old ileal-cannulated calves that were enrolled in a 3 × 3 replicated Latin square with 5-d periods. The 3 diets were a control whey protein-based MR (WPC), an isonitrogenous MR in which 50% of the protein was from enzyme-treated soybean meal (ESBM), and an N-free MR (NFREE). Mucin protein concentration and flow were analyzed by fractionation of the digesta and ethanol precipitation; this process served as the reference method. Alternative methods to estimate MUP consisted of using commercial enzymatic kits to analyze glucosamine (N-acetylglucosamine, GlcNAc) and galactosamine (N-acetylgalactosamine, GalNAc), 2 amino-sugars that are highly enriched in mucin. Before GlcNAc determination, samples were processed using 3 different procedures: sample clarification (GLCL), clarification plus hydrolysis (GLCH), and hydrolysis alone (GLHL). The MUP was estimated by regression of the GlcNAc and GalNAc values using previously validated equations. According with the bias and agreement analysis, none of the methods yielded MUP values similar to the reference method. However, GLHL showed a strong association with the reference method (ρ = 0.73). It allowed identifying the smaller MUP flows with NFREE compared with the other 2 diets and detecting the greater flow of ESBM than WPC, as observed with the reference method. Using the GlcNAc values from GLHL and the MUP measured with the reference method, we were able to establish a linear relationship between both methods (adjusted R2 = 0.75). We found that the GLHL method enabled detecting differences in MUP ileal flows between diets differing in protein level and source. Inferences about MUP secretions must be done cautiously because many dietary and physiological factors are involved. The adoption of practical techniques to determine MUP can help to increase our knowledge about gastrointestinal tract function and to improve the accuracy of MR digestibility calculations.

An Overview of the Elusive Passenger in the Gastrointestinal Tract of Cattle: The Shiga Toxin Producing Escherichia coli

For approximately 10,000 years, cattle have been our major source of meat and dairy. However, cattle are also a major reservoir for dangerous foodborne pathogens that belong to the Shiga toxin-producing Escherichia coli (STEC) group. Even though STEC infections in humans are rare, they are often lethal, as treatment options are limited. In cattle, STEC infections are typically asymptomatic and STEC is able to survive and persist in the cattle GIT by escaping the immune defenses of the host. Interactions with members of the native gut microbiota can favor or inhibit its persistence in cattle, but research in this direction is still in its infancy. Diet, temperature and season but also industrialized animal husbandry practices have a profound effect on STEC prevalence and the native gut microbiota composition. Thus, exploring the native cattle gut microbiota in depth, its interactions with STEC and the factors that affect them could offer viable solutions against STEC carriage in cattle.

Ileal digestibility and endogenous protein losses of milk replacers based on whey proteins alone or with an enzyme-treated soybean meal in young dairy calves

Our objective was to measure and compare apparent ileal digestibility, standard ileal digestibility, and true ileal digestibility of crude protein (CP) and amino acids (AA) in milk replacers (MR) containing all milk proteins (WPC) or with 50% of the CP provided by an enzyme-treated soybean meal (ESBM). A T-cannula was placed in the ileum of 9 Holstein calves (8 males and 1 freemartin female) at approximately 15 d of age. After 2 wk postsurgery, calves were randomly assigned to a 3 × 3 replicated Latin square with 5-d periods. Calves were fed twice daily at a rate of 2% (dry matter) of body weight (1.25 kg/d on average), reconstituted to 15% solids, and adjusted weekly. No starter was offered to minimize rumen development. Digesta samples were collected continuously during 12 h on d 4 and 5 of each period. Basal endogenous losses of AA and CP were estimated by feeding an N-free MR to each calf during 1 period. Total endogenous losses (basal + specific; ENDtotal) were estimated by multivariate regression of the chi-squared distances between digesta and reference protein AA profiles. Ileal digesta pH with the ESBM diet was lower than that with the WPC diet. According to the piecewise nonlinear model of pH fluctuation, digesta pH during ESBM decreased more slowly after feeding and reached its nadir later than with the WPC diet. Diet did not affect average daily gain, but calves on the ESBM diet showed a bigger increment of withers height and lower mean fecal scores. The basal endogenous losses of AA and CP were 13.9 ± 1.1 and 22.4 ± 1.1 g/kg of dry matter intake, respectively. The estimated ENDtotal of AA and CP was higher with ESBM than with WPC. Accordingly, apparent ileal digestibility and standard ileal digestibility of most AA, CP, and total AA were lower or tended to be lower with ESBM. However, true ileal digestibility did not differ between diets for CP and all AA except Ala and Ile, which were greater with WPC, and Arg, which tended to be greater with ESBM. In agreement with the estimated differences in ENDtotal, we found that flows of digesta DNA and crude mucin were greater with ESBM. Substitution of 50% of the protein from whey with enzymatically treated soybean meal did not affect major nutrient digestibility or calf growth and even improved fecal consistency. Adjusting digestibilities of CP and AA in MR by endogenous protein losses is crucial when comparing bioavailability of alternative proteins and milk proteins.

Transcriptomic analysis reveals specific metabolic pathways of enterohemorrhagic Escherichia coli O157:H7 in bovine digestive contents

Background

The cattle gastrointestinal tract (GIT) is the main enterohemorrhagic Escherichia coli (EHEC) reservoir. In order to identify nutrients required for the survival or multiplication of EHEC in the bovine GIT, we compared the transcriptomes of the EHEC O157:H7 reference strain EDL933 cultured in vitro in bovine digestive contents (DCs) (rumen, small intestine and rectum) using RNA-sequencing.

Results

Gene expression profiles showed that EHEC EDL933 activated common but also specific metabolic pathways to survive in the different bovine DCs. Mucus-derived carbohydrates seem important in EHEC nutrition in posterior DCs (small intestine and rectum) but not in rumen content. Additional carbohydrates (xylose, ribose, mannitol, galactitol) as well as gluconeogenic substrates (aspartate, serine, glycerol) would also be used by EHEC as carbon and/or nitrogen sources all along the bovine GIT including the rumen. However, xylose, GalNac, ribose and fucose transport and/or assimilation encoding genes were over-expressed during incubation in rectum content compared with rumen and intestine contents, and genes coding for maltose transport were only induced in rectum. This suggests a role for these carbohydrates in the colonization of the cattle rectum, considered as the major site for EHEC multiplication. In contrast, the transcription of the genes associated with the assimilation of ethanolamine, an important nitrogen source for EHEC, was poorly induced in EHEC growing in rectum content, suggesting that ethanolamine is mainly assimilated in the cattle rumen and small intestine. Respiratory flexibility would also be required for EHEC survival because of the redundancy of dehydrogenases and reductases simultaneously induced in the bovine DCs, probably in response to the availability of electron donors and acceptors.

Conclusion

EHEC EDL933 showed a high flexibility in the activation of genes involved in respiratory pathways and assimilation of carbon and nitrogen sources, most of them from animal origin. This may allow the bacterium to adapt and survive in the various bovine GIT compartments. Obtaining a better understanding of EHEC physiology in bovine GIT is a key step to ultimately propose strategies to limit EHEC carriage and shedding by cattle.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5167-y) contains supplementary material, which is available to authorized users.

Mucus-Pathogen Interactions in the Gastrointestinal Tract of Farmed Animals

Gastrointestinal infections cause significant challenges and economic losses in animal husbandry. As pathogens becoming resistant to antibiotics are a growing concern worldwide, alternative strategies to treat infections in farmed animals are necessary in order to decrease the risk to human health and increase animal health and productivity. Mucosal surfaces are the most common route used by pathogens to enter the body. The mucosal surface that lines the gastrointestinal tract is covered by a continuously secreted mucus layer that protects the epithelial surface. The mucus layer is the first barrier the pathogen must overcome for successful colonization, and is mainly composed of densely glycosylated proteins called mucins. The vast array of carbohydrate structures present on the mucins provide an important setting for host-pathogen interactions. This review summarizes the current knowledge on gastrointestinal mucins and their role during infections in farmed animals. We examine the interactions between mucins and animal pathogens, with a focus on how pathogenic bacteria can modify the mucin environment in the gut, and how this in turn affects pathogen adhesion and growth. Finally, we discuss analytical challenges and complexities of the mucus-based defense, as well as its potential to control infections in farmed animals.

Genomic analysis of three Bifidobacterium species isolated from the calf gastrointestinal tract

Ruminant animals contribute significantly to the global value of agriculture and rely on a complex microbial community for efficient digestion. However, little is known of how this microbial-host relationship develops and is maintained. To begin to address this, we have determined the ability of three Bifidobacterium species isolated from the faeces of newborn calves to grow on carbohydrates typical of a newborn ruminant diet. Genome sequences have been determined for these bacteria with analysis of the genomes providing insights into the host association and identification of several genes that may mediate interactions with the ruminant gastrointestinal tract. The present study provides a starting point from which we can define the role of potential beneficial microbes in the nutrition of young ruminants and begin to influence the interactions between the microbiota and the host. The differences observed in genomic content hint at niche partitioning among the bifidobacterial species analysed and the different strategies they employ to successfully adapt to this habitat.

Enteric Pathogens Exploit the Microbiota-generated Nutritional Environment of the Gut

Host bacterial associations have a profound impact on health and disease. The human gastrointestinal (GI) tract is inhabited by trillions of commensal bacteria that aid in the digestion of food and vitamin production and play crucial roles in human physiology. Disruption of these relationships and the structure of the bacterial communities that inhabit the gut can contribute to dysbiosis, leading to disease. This fundamental relationship between the host and microbiota relies on chemical signaling and nutrient availability and exchange. GI pathogens compete with the endogenous microbiota for a colonization niche (1, 2). The ability to monitor nutrients and combine this information with the host physiological state is important for the pathogen to precisely program the expression of its virulence repertoire. A major nutrient source is carbon, and although the impact of carbon nutrition on the colonization of the gut by the microbiota has been extensively studied, the extent to which carbon sources affect the regulation of virulence factors by invading pathogens has not been fully defined. The GI pathogen enterohemorrhagic E. coli (EHEC) gages sugar sources as an important cue to regulate expression of its virulence genes. EHEC senses whether it is in a gluconeogenic versus a glycolytic environment, as well as fluctuations of fucose levels to fine tune regulation of its virulence repertoire.

Interactive effects of dietary protein concentration and aflatoxin B1 on performance, nutrient digestibility, and gut health in broiler chicks

A 20-day trial was conducted to determine the impact of aflatoxin B1 (AFB1) and dietary protein concentration on performance, nutrient digestibility, and gut health in broiler chicks. The 6 dietary treatments were arranged in a 2 × 3 factorial with 3 crude protein (CP) concentrations (16, 22, and 26%) with or without 1.5 mg/kg AFB1 Each diet was fed to 6 replicate cages (6 chicks per cage) from zero to 20 d of age. Endogenous N and amino acid loss were estimated from birds fed a N-free diet with or without 1.5 mg/kg AFB1 A significant interaction between AFB1 and CP concentration was observed for growth performance, where reduction of BW gain, feed intake, gain:feed ratio, and breast muscle weight by AFB1 were most profound in birds fed the 16%-CP diet, and were completely eliminated when birds were fed the 26%-CP diet (AFB1 by CP interaction; P ≤ 0.023). Similarly, AFB1 reduced serum albumin, total protein, and globulin concentrations in birds fed 16 and 22% CP diets, but not in those fed the 26%-CP (AFB1 by CP interaction; P ≤ 0.071). Gut permeability was increased in birds fed AFB1-contamiated diets as measured by serum lactulose/rhamnose ratio (main effect; P = 0.04). Additionally, AFB1 tended to increase endogenous N loss (P = 0.09), and significantly reduced apparent ileal digestible energy and standardized ileal N and amino acid digestibility in birds fed the 16%-CP diet, while birds fed higher dietary CP were not affected (AFB1 by CP interaction; P ≤ 0.01). Further, AFB1 increased the translation initiation factor 4E-binding protein (4EBP1), claudin1, and multiple jejunal amino acid transporters expression (main effect; P ≤ 0.04). Results from this study indicate that a 1.5 mg AFB1/kg diet significantly impairs growth, major serum biochemistry measures, gut barrier, endogenous loss, and energy and amino acid digestibility. Aflatoxicosis can be augmented by low dietary CP, while higher dietary CP completely eliminated the impairment of performance, serum proteins, and nutrient digestibility from aflatoxicosis in zero to 20 d broiler chicks.

The gluconeogenesis pathway is involved in maintenance of enterohaemorrhagic Escherichia coli O157:H7 in bovine intestinal content

Enterohaemorrhagic Escherichia coli (EHEC) are responsible for outbreaks of food- and water-borne illness. The bovine gastrointestinal tract (GIT) is thought to be the principle reservoir of EHEC. Knowledge of the nutrients essential for EHEC growth and survival in the bovine intestine may help in developing strategies to limit their shedding in bovine faeces thus reducing the risk of human illnesses. To identify specific metabolic pathways induced in the animal GIT, the transcriptome profiles of EHEC O157:H7 EDL933 during incubation in bovine small intestine contents (BSIC) and minimal medium supplemented with glucose were compared. The transcriptome analysis revealed that genes responsible for the assimilation of ethanolamine, urea, agmatine and amino acids (Asp, Thr, Gly, Ser and Trp) were strongly up-regulated suggesting that these compounds are the main nitrogen sources for EHEC in BSIC. A central role for the gluconeogenesis pathway and assimilation of gluconeogenic substrates was also pinpointed in EHEC incubated in BSIC. Our results suggested that three amino acids (Asp, Ser and Trp), glycerol, glycerol 3-phosphate, L-lactate and C4-dicarboxylates are important carbon sources for EHEC in BSIC. The ability to use gluconeogenic substrates as nitrogen sources (amino acids) and/or carbon sources (amino acids, glycerol and lactate) may provide a growth advantage to the bacteria in intestinal fluids. Accordingly, aspartate (2.4 mM), serine (1.9 mM), glycerol (5.8 mM) and lactate (3.6 mM) were present in BSIC and may represent the main gluconeogenic substrates potentially used by EHEC. A double mutant of E. coli EDL933 defective for phosphoenolpyruvate synthase (PpsA) and phosphoenolpyruvate carboxykinase (PckA), unable to utilize tricarboxylic acid (TCA) intermediates was constructed. Growth competition experiments between EHEC EDL933 and the isogenic mutant strain in BSIC clearly showed a significant competitive growth advantage of the wild-type strain further illustrating the importance of the gluconeogenesis pathway in maintaining EHEC in the bovine GIT.

Capacity of the bovine intestinal mucus and its components to support growth of Escherichia coli O157:H7

Colonization of the gastrointestinal tract of cattle by Shiga toxin-producing Escherichia coli increases the risk of contamination of food products at slaughter. Our study aimed to shed more light on the mechanisms used by E. coli O157:H7 to thrive and compete with other bacteria in the gastrointestinal tract of cattle. We evaluated, in vitro, bovine intestinal mucus and its constituents in terms of their capacity to support growth of E. coli O157:H7 in presence or absence of fecal inoculum, with and without various enzymes. Growth of E. coli O157:H7 and total anaerobic bacteria were proportionate to the amount of mucus added as substrate. Growth of E. coli O157:H7 was similar for small and large intestinal mucus as substrate, and was partially inhibited with addition of fecal inoculum to cultures, presumably due to competition from other organisms. Whole mucus stimulated growth to the greatest degree compared with other compounds evaluated, but the pathogen was capable of utilizing all substrates to some extent. Addition of enzymes to cultures failed to impact growth of E. coli O157:H7 except for neuraminidase, which resulted in greater growth of E. coli O157 when combined with sialic acid as substrate. In conclusion, E. coli O157 has capacity to utilize small or large intestinal mucus, and growth is greatest with whole mucus compared with individual mucus components. There are two possible explanations for these findings (i) multiple substrates are needed to optimize growth, or alternatively, (ii) a component of mucus not evaluated in this experiment is a key ingredient for optimal growth of E. coli O157:H7.

Characterization of a surface glycoprotein from Echinococcus multilocularis and its mucosal vaccine potential in dogs

Alveolar echinococcosis is a refractory disease caused by the metacestode stage of Echinococcus multilocularis. The life cycle of this parasite is maintained primarily between foxes and many species of rodents; thus, dogs are thought to be a minor definitive host except in some endemic areas. However, dogs are highly susceptible to E. multilocularis infection. Because of the close contact between dogs and humans, infection of dogs with this parasite can be an important risk to human health. Therefore, new measures and tools to control and prevent parasite transmission required. Using 2-dimensional electrophoresis followed by western blot (2D-WB) analysis, a large glycoprotein component of protoscoleces was identified based on reactivity to intestinal IgA in dogs experimentally infected with E. multilocularis. This component, designated SRf1, was purified by gel filtration using a Superose 6 column. Glycosylation analysis and immunostaining revealed that SRf1 could be distinguished from Em2, a major mucin-type antigen of E. multilocularis. Dogs (n = 6) were immunized intranasally with 500 µg of SRf1 with cholera toxin subunit B by using a spray syringe, and a booster was given orally using an enteric capsule containing 15 mg of the same antigen. As a result, dogs immunized with this antigen showed an 87.6% reduction in worm numbers compared to control dogs (n = 5) who received only PBS administration. A weak serum antibody response was observed in SRf1-immunized dogs, but there was no correlation between antibody response and worm number. We demonstrated for the first time that mucosal immunization using SRf1, a glycoprotein component newly isolated from E. multilocularis protoscoleces, induced a protection response to E. multilocularis infection in dogs. Thus, our data indicated that mucosal immunization using surface antigens will be an important tool to facilitate the development of practical vaccines for definitive hosts.

Influence of L-threonine supplementation on goblet cell numbers, histological structure and antioxidant enzyme activities of laying hens reared in a hot and humid climate

1. A previous experiment in our laboratory found that L-threonine supplementation at 0.2 and 0.3% increased egg production and the concentration of serum IgG, respectively. The objective of this current trial was to determine if both supplementation levels can positively influence histological structure, goblet cell numbers, or antioxidant enzyme activities. 2. Babcock Brown layers (n=576), 40 weeks of age, were allocated to three treatment groups, each of which included 6 replicates of 32 hens. Each group received the same basal diet formulated with maize, peanut meal and crystalline amino acids. L-threonine was added to the basal diet at 0 (control), 0.2, and 0.3%, respectively for 8 weeks. Chemical analysis of the diets for threonine values were 0.47, 0.66 and 0.74 %, respectively. 3. The numbers of goblet cells did not change due to L-threonine supplementation. Also, L-threonine had no affect on the villus height and mucosal thickness. No differences were found due to treatments among groups in the activity of alkaline phosphatase (ALP) in jejunum or ileum. L-threonine supplementation at 0.2% maximised the concentration of superoxide dismutases (SOD) in both serum and liver. 4. In conclusion, L-threonine supplementation had no affect on gut morphology but may have an antioxidant function at 0.2%.

Modulation of intestinal mucin composition and mucosal morphology by dietary phytogenic inclusion level in broilers

The effect of a dietary phytogenic feed additive (PFA) inclusion level in mucin monosaccharide composition, mucosal morphometry and mucus histochemistry along the broiler intestinal tract was studied. Cobb male broilers (n = 525) were allocated into five experimental treatments that, depending on the type of addition in the basal diet (BD), were labeled as follows: C (BD based on maize-soybean meal with no other additions), E1 (80 mg PFA/kg BD), E2 (125 mg PFA/kg BD), E3 (250 mg PFA/kg of BD) and A (2.5 mg avilamycin/kg BD). Samples from duodenum, ileum and cecum of 14- and 42-day-old broilers were collected and analyzed. In 14-day-old broilers, treatments E2 and E3 had higher (P < 0.01) duodenal mannose than treatments C, E1 and A. Ileal mannose was lower (P < 0.05) in treatment C compared with PFA treatments, and ileal galactose (Gal) was higher (P < 0.01) in treatments E2 and E3 compared with C and A. Polynomial contrast analysis with respect to PFA inclusion level showed that in 14-day-old broilers there was a linear increase (P = 0.001) in duodenal mannose and a quadratic effect (P = 0.038) in duodenal N-acetyl-galactosamine with increasing PFA level. Ileal Gal and mannose increased linearly (P = 0.002 and P = 0.012, respectively) with PFA inclusion level. There were no significant differences between treatments in mucin monosaccharide molar ratios of 42-day-old broilers. However, increasing PFA inclusion level resulted in a linear decrease of ileal fucose (P = 0.021) and cecal N-acetylgalactosamine (P = 0.036). Experimental treatments did not differ (P > 0.05) regarding duodenal villus height (Vh), crypt depth (Cd) and Vh/Cd ratio, irrespective of broiler age and the intestinal segment examined. However, increasing dietary PFA inclusion level showed a pattern of linear increase of duodenal Vh/Cd ratio in 14-day-old broilers and ileal Vh in 42-day-old broilers (P = 0.039 and P = 0.039, respectively). Alcian Blue-Periodic Acid-Schiff (pH 2.5) staining of neutral and acidic mucins showed that the staining intensity of mucus layer in villi was fragment (i.e. tip, midsection and base) dependent, whereas in crypts it was dependent both on intestinal segment (i.e. duodenum, ileum and cecum) and fragment. Finally, mucus layer thickness did not differ (P > 0.05) between treatments, yet a pattern of linear increase (P < 0.05) with PFA inclusion level was observed in the duodenum of 42-day-old broilers. In conclusion, the dietary inclusion level of PFA modulated broiler intestinal mucin composition and morphology. Further studies are required to elucidate the physiological implications of such changes in host-microflora interactions.

[EHEC carriage in ruminants and probiotic effects]

Enterohaemorrhagic Escherichia coli (EHEC) are Shiga-Toxin producing E. coli (STEC) that cause human outbreaks which can lead to a severe illness such as haemolytic-uraemic syndrome (HUS), particularly in young children. The gastrointestinal tract of cattle and other ruminants is the principal reservoir of EHEC strains and outbreaks have been associated with direct contact with the farm environment, and with the consumption of meat, dairy products, water and fruit or vegetable contaminated with ruminant manure. Several outbreaks occurred these last years in France. In Brazil, although STEC carriage in ruminants is important, human cases due to EHEC are fairly rare. In order to reduce EHEC survival in the ruminant gastrointestinal tract and thus limit contamination of food products, it is necessary to determine the mechanisms underlying EHEC persistence in this ecosystem with the aim of developing nutritional or ecological strategies. The effect of probiotics has been tested in vitro on the growth and survival of EHEC strains and in vivo on the animal carriage of these strains. Various studies have then shown that lactic bacteria or non-pathogenic E. coli strains were able to limit EHEC fecal shedding. In addition, understanding EHEC physiology in the ruminant gut is also critical for limiting EHEC shedding. We found that EHEC O157:H7 is able to use ethanolamine and mucus-derived sugars as nitrogen and carbon sources, respectively. Thus, these substrates represent an ecological niche for EHEC and their utilization confers a competitive growth advantage to these pathogens as they use them more rapidly than the bacteria belonging to the resident intestinal microbiota. Understanding EHEC metabolism and ecology in the bovine intestinal tract will allow proposing probiotic strains to compete with EHEC for nutrients and thus decrease the sanitary risk.

Carbohydrate utilization by enterohaemorrhagic Escherichia coli O157:H7 in bovine intestinal content

The bovine gastrointestinal (GI) tract is the main reservoir for enterohaemorrhagic Escherichia coli (EHEC) responsible for food-borne infections. Characterization of nutrients preferentially used by EHEC in the bovine intestine would help to develop ecological strategies to reduce EHEC carriage. However, the carbon sources that support the growth of EHEC in the bovine intestine are poorly documented. In this study, a very low concentration of glucose, the most abundant monomer included in the cattle dietary polysaccharides, was detected in bovine small intestine contents (BSIC) collected from healthy cows at the slaughterhouse. Six carbohydrates reported to be included in the mucus layer covering the enterocytes [galactose, N-acetyl-glucosamine (GlcNAc), N-acetyl- galactosamine (GalNAc), fucose, mannose and N-acetyl neuraminic acid (Neu5Ac)] have been quantified for the first time in BSIC and accounted for a total concentration of 4.2 mM carbohydrates. The genes required for enzymatic degradation of the six mucus-derived carbohydrates are highly expressed during the exponential growth of the EHEC strain O157:H7 EDL933 in BSIC and are more strongly induced in EHEC than in bovine commensal E. coli. In addition, EDL933 consumed the free monosaccharides present in the BSIC more rapidly than the resident microbiota and commensal E. coli, indicating a competitive ability of EHEC to catabolize mucus-derived carbohydrates in the bovine gut. Mutations of EDL933 genes required for the catabolism of each of these sugars have been constructed, and growth competitions of the mutants with the wild-type strain clearly demonstrated that mannose, GlcNAc, Neu5Ac and galactose catabolism confers a high competitive growth advantage to EHEC in BSIC and probably represents an ecological niche for EHEC strains in the bovine small intestine. The utilization of these mucus-derived monosaccharides by EDL933 is apparently required for rapid growth of EHEC in BSIC, and for maintaining a competitive growth rate as compared with that of commensal E. coli. The results suggest a strategy for O157:H7 E. coli survival in the bovine intestine, whereby EHEC rapidly consumes mucus-derived carbohydrates that are poorly consumed by bacteria belonging to the resident intestinal microbiota, including commensal E. coli.

Morphometric features and glycoconjugate pattern of rabbit intestine are affected by particle size of pelleted diets

Feed particle size effects on morphology and glycoconjugate pattern was investigated in the rabbit intestine. Rabbits fed with fine particles (2 mm) displayed more irregularly shaped, higher duodenal villi and deeper crypts in distal colon as well as higher number of goblet cells than coarse (8 mm) fed ones. Brush border expressed: (i) in duodenum, neutral/sulfated glycoconjugates and glycans binding MAL II, SNA, Con A than KOH-sialidase-PNA and DBA reactivity in fine and coarse fed rabbits, respectively, (ii) in cecum, mainly sulfoglycans in coarse fed rabbits, MAL II and PNA staining in all samples, and (iii) in distal colon few sulfoglycans and MAL II reactivity. Enterocytes bound MAL II in duodenum, Con A in cecum, DBA, and Con A in distal colon of all rabbits, SNA in distal colon of coarse fed ones. Brunner's glands displayed high presence of acidic/sulfated mucins in fine fed rabbits, neutral glycoconjugates and reactivity with MAL II, SNA, PNA, KOH-sialidase-PNA, and Con A in all rabbits. Goblet cells exhibited: (i) in duodenum neutral and sulfomucins as well as MAL II and KOH-sialidase-PNA staining, than SNA and DBA in fine and coarse fed rabbits, respectively, (ii) in cecum sulfated glycans, MAL II, SNA, KOH-sialidase-PNA, DBA reactivity, and (iii) in distal colon acidic/sulfomucins, MAL II and SNA staining, and DBA reactivity in fine fed specimens. Crypt cells exhibited neutral and PNA reactive glycoconjugates in the cecum. In the distal colon also acidic/sulfated glycans, and MAL II, KOH-sialidase-PNA, DBA; SNA staining showed weaker reactivity in fine fed rabbits, which bound Con A.

Echinococcus multilocularis: purification and characterization of glycoprotein antigens with serodiagnostic potential for canine infection

We show that a conventionally purified glycoprotein component of Echinococcus multilocularis protoscolex, designated as Emgp-89, may be useful as a serodiagnostic antigen for detecting E. multilocularis infection in dogs domesticated in endemic areas. Emgp-89 was obtained from the parasite material by a simple procedure using Con A-agarose and subsequent gel filtration chromatography. The purified fraction showed a molecular weight of >4000kDa upon gel filtration and reacted with a series of lectins that specifically bind to mannose, galactose, N-acetylglucosamine, and N-acetylgalactosamine. Subsequently, serodiagnostic performance of Emgp-89 was evaluated through enzyme-linked immunosorbent assays (ELISAs) by using sera from normal, domestic dogs and dogs infected with other helminths. Emgp-89 positively reacted with all 16 serum samples from E. multilocularis-infected dogs, thus showing that this antigen is highly sensitive. On the other hand, the specificity of Emgp-89-based ELISA, determined using 41 serum samples from dogs infected with other helminths, was relatively low (83%). As an attempt to improve the specificity of Emgp-89-based ELISA, we pretreated Emgp-89 with proteinase K or sodium periodate, expecting that these treatments would enable discrimination of true positives from false positives. The ELISA value increased after treatment with sodium periodate in most false-positive samples, whereas significant decreases were observed in sera from all dogs infected with E. multilocularis. Further evaluation of this antigen should be performed using sera from dogs infected with closely-related parasites, including taeniid cestodes, which are expected to prove that this serodiagnostic system is sufficiently specific for clinical and field applications.

Development and validation of a continuous in vitro system reproducing some biotic and abiotic factors of the veal calf intestine

Following the January 2006 European ban of antibiotics used as growth promoters in the veal calf industry, new feed additives are needed in order to maintain animal health and growth performance. As an alternative to in vivo experiments in the testing of such additives, an in vitro system modeling the intestinal ecosystem of the veal calf was developed. Stabilization of the main cultured microbial groups and their metabolic activity were tracked in an in vitro continuous fermentor operated under anaerobiosis, at pH 6.5, and at a temperature of 38.5 degrees C and supplied with one of three different nutritive media (M1, M2, or M3). These media mainly differed in their concentrations of simple and complex carbohydrates and in their lipid sources. In vitro microbial levels and fermentative metabolite concentrations were compared to in vivo data, and the biochemical composition of the nutritive media was compared to that of the veal calf intestinal content. All three nutritive media were able to stabilize anaerobic and facultative anaerobic microflora, lactate-utilizing bacteria, bifidobacteria, lactobacilli, enterococci, and Bacteroides fragilis group bacteria at levels close to in vivo values. The microbiota was metabolically active, with high concentrations of lactate, ammonia, and short-chain fatty acids found in the fermentative medium. Comparison with in vivo data indicated that M3 outperformed M1 and M2 in simulating the conditions encountered in the veal calf intestine. This in vitro system would be useful in the prescreening of new feed additives by studying their effect on the intestinal microbiota levels and fermentative metabolite production.

Intestinal mucin dynamics: response of broiler chicks and White Pekin ducklings to dietary threonine

Mucin dynamics may be particularly sensitive to a Thr deficiency due to the high concentration and structural importance of Thr in the mucin protein backbone. Intestinal mucin secretion, expression of mucin gene (MUC2), and histological characteristics were investigated in male broilers and White Pekin ducklings offered diets containing 3.3, 5.8, or 8.2 g of Thr/kg in 4 studies. Seventy-two birds of each species were fed a standard broiler starter diet from 1 to 14 d of age followed by assignment to 3 dietary treatments in a randomized complete block design for a 7-d feeding trial in experiment 1 (broilers) and experiment 2 (ducklings). The dietary treatments consisted of an isonitrogenous corn-soybean meal-based diet with the addition of crystalline amino acids and graded levels of Thr. Dietary treatments contained 3.3, 5.8, or 8.2 g of Thr/kg. Dietary formulation and experimental design for experiments 3 (broilers) and 4 (ducklings) were similar to experiments 1 and 2 except that birds were fed 3.3 or 8.2 g of Thr/kg for durations of 7 or 14 d. For chicks, increased dietary Thr resulted in higher levels of intestinal crude mucin excretion in experiment 1 (P=0.04) but not in experiment 3, whereas intestinal sialic acid excretion increased in experiment 3 (P=0.02) but not in experiment 1. Furthermore, there was no effect of Thr on intestinal goblet cell density or MUC2 mRNA abundance for broilers. For ducklings, there was an increase in intestinal crude mucin excretion in both experiments (P<0.05) as dietary Thr increased, although there was no effect of Thr on intestinal sialic acid excretion. There was a tendency for an increase in intestinal goblet cell density (cells/microm of villus length; P=0.09) as dietary Thr increased in experiment 2. For experiment 4, intestinal MUC2 mRNA abundance increased (P=0.03) as dietary Thr increased for the 14-d feeding trial but not for the 7-d feeding trial. The data establish a link between dietary Thr and intestinal crude mucin dynamics in chicks for experiment 1 and ducklings for both experiments.

Intestinal inflammation increases gastrointestinal threonine uptake and mucin synthesis in enterally fed minipigs

The high requirement of the gut for threonine has often been ascribed to the synthesis of mucins, secreted threonine-rich glycoproteins protecting the intestinal epithelium from injury. This requirement could be even greater during intestinal inflammation, when mucin synthesis is enhanced. In this study, we used an animal model to investigate the effects of an acute ileitis on threonine splanchnic fluxes. Eight adult multi-catheterized minipigs were fed with an enteral solution. Four of them were subjected to experimental ileitis involving direct administration of trinitrobenzene sulfonic acid (TNBS) into the ileum (TNBS-treated group) and the other 4 were not treated (control group). Threonine fluxes across the portal-drained viscera (PDV) were quantified with the use of simultaneous i.g. L-[(15)N]threonine and i.v. L-[U-(13)C]threonine infusions. Ileal mucosa was sampled for mucin fractional synthesis rate measurement, which was greater in the TNBS-treated group (114 +/- 15%/d) than in the control group (61 +/- 8%/d) (P = 0.021). The first-pass extraction of dietary threonine by the PDV and liver did not differ between groups and accounted for approximately 27 and 10% of the intragastric delivery, respectively. PDV uptake of arterial threonine increased from 25 +/- 14 micromol x kg(-1) x h(-1) in the control group to 171 +/- 35 micromol x kg(-1) x h(-1) in the TNBS-treated group (P < 0.001). In conclusion, ileitis increased intestinal mucin synthesis and PDV utilization of threonine from arterial but not luminal supply. This leads to the mobilization of endogenous proteins to meet the increased threonine demand associated with acute intestinal inflammation.

Enumeration of some cultivable bacterial groups and characterization of some abiotic variables in the jejunoileal content of Prim'Holstein veal calves

A study was conducted to characterize the bacterial and biochemical composition of the jejunoileal content of veal calves and the effect of pre-slaughter fasting time. At 22 wk of age, 22 preruminant Prim'Holstein calves fed milk replacer and pellets (mainly composed of corn) were slaughtered at 6, 12, or 24 h after their last meal. Chyme samples were collected from the jejunoileal compartment just after slaughter, and pH and redox potential were immediately measured. Culture-based methods were used to determine the concentrations of total anaerobic microflora, lactate-utilizing bacteria, Bacteroides fragilis group, Lactobacilli, Bifidobacteria, Enterococci, and 2 potential pathogenic species, Escherichia coli and Clostridium perfringens. Concentrations of l-lactate, ammonia, and short-chain fatty acids (SCFA) were determined on frozen samples. The biochemical composition (DM, total protein, lactose, galactose, glucose, minerals, AA profile, and fatty acid profile) of the jejunoileal content was determined only on samples from the 6-h fasted group. Microflora concentrations were greater (P < 0.01) in the 6-h fasted group compared with the 12- and 24-h fasted groups, involving a decreased pH (P < 0.05) and greater lactate and SCFA concentrations, both linked directly to the fermentative state of the microorganisms. The 6-h fasted group showed the least interanimal variability in bacterial group levels, except for Cl. perfringens, which presented increased interanimal variability regardless of fasting time. At 6 h postprandial, the jejunoileal content of veal calves seemed to be in a stable state, allowing the creation of a database on its biochemical composition. This study is a key first step in the development of an in vitro system for modeling the jejunoileal ecosystem of veal calves. This model will provide a useful tool for assessing the effects of feed additives on intestinal microflora.

Effects of mucin and its carbohydrate constituents on Escherichia coli O157 growth in batch culture fermentations with ruminal or fecal microbial inoculum

In cattle, Escherichia coli O157 generally persists in the large intestine more often than in the rumen. In contrast to the rumen, the large intestine is lined by an epithelial membrane that secretes mucus. We hypothesize that substrates contained in intestinal mucus may constitute a source of energy that is preferentially used by E. coli O157. Therefore, our objective was to test the effects of mucin and its carbohydrate constituents on in vitro growth of E. coli O157 in ruminal or fecal microbial fermentations. Ruminal contents and feces were collected from a ruminally cannulated donor steer fed a corn grain-based finishing diet. Ruminal contents were strained through 2 layers of cheesecloth and incubated at 39 degrees C for 1 h; the floating hay mat was removed with a vacuum suction; and the remaining material was utilized as rumen microbial inoculum. Feces were suspended in physiologic saline to increase fluidity, blended, and strained through 2 layers of cheesecloth. The resulting fluid was utilized as fecal microbial inoculum. Fermentations (50 mL) were performed in serum bottles with a 2:1 mineral buffer to microbial inoculum ratio. Substrates (mucin, fucose, galactose, mannose, gluconic acid, galacturonic acid, glucuronic acid, galactosamine, and glucosamine) were added at 10 mg/mL. A mixture of 5 strains of nalidixic acid-resistant (Nal(R)) E. coli O157 strains was added to each fermentation and concentrations were determined after 0, 6, 12, and 24 h of incubation. In ruminal fermentations, fucose, mannose, glucuronic acid, galacturonic acid, glucosamine, galactosamine, and mucin had no effect on Nal(R) E. coli O157 concentration compared with the control (no substrate added) fermentation. At 24 h of fermentation, the mean concentration of Nal(R) E. coli O157 in fermentations with galactose was less than the control. However, including gluconic acid as substrate increased Nal(R) E. coli O157 concentration at 24 h. In fecal fermentations, mannose, galactose, gluconic acid, glucuronic acid, galacturonic acid, glucosamine, and mucin increased Nal(R) E. coli O157 growth compared with control at 24 h, whereas galactosamine and fucose did not. Gluconic acid was the most stimulatory substrate, increasing Nal(R) E. coli O157 by more than 1.0 log in ruminal fermentations and 2.0 log in fecal fermentations. In summary, availability of mucous constituents, particularly gluconic acid, may explain the greater prevalence of E. coli O157 in the large intestine compared with the rumen of the digestive tract.

Diets Containing Escherichia coli-Derived Phytase on Young Chickens and Turkeys: Effects on Performance, Metabolizable Energy, Endogenous Secretions, and Intestinal Morphology

The aim of this experiment was to compare the responses of young broiler chickens directly with the responses of turkeys to different dietary phytase concentrations. Nine hundred sixty birds (480 female Ross 308 broilers, and 480 female BUT6 turkeys) were reared in 64 floor pens from 0 to 21 d of age. Each species was fed a nutritionally complete (12.79 MJ/kg of AME, 231 g/kg of CP vs. 11.75 MJ/kg of AME, 285 g/kg of CP for chickens and turkeys, respectively), low-P (28 and 37 g/kg available P for chickens and turkeys, respectively) corn (maize)-soy feed supplemented with either 0, 250, 500, or 2,500 phytase units (phytase/kg of feed) to give a total of 4 diets per species. The study was conducted in a split-plot design and each dietary treatment was replicated 8 times. Performance, AME, sialic acid (SA) excretions, and ileal villus morphology of 21-d-old broiler chickens and turkeys were determined. Overall, chickens grew faster and consumed more than turkeys throughout the study period. Dietary enzyme concentrations linearly increased the feed intake and weight gain of birds. The results were improved, on average, as follows: feed intake by 11.2 and 6.5%, gain by 10.2 and 13.2%, feed efficiency by 0 and 7.6%, AME by 1.4 and 5.7%, and AME intake by 13.1 and 9.8% for chickens and turkeys, respectively. The AME data were subject to a species x phytase interaction, whereby increasing the phytase dosage led to significant increments in parameters for turkeys but not broilers; broilers recovered significantly more energy from the ration than did turkeys. A quadratic relationship existed between dietary AME and phytase concentrations. Turkeys excreted more SA than did chickens in the absence of phytase, whereas supplementation with phytase (250 and 500 phytase units) reduced the excretion of SA in turkeys. Enzyme supplementation did not affect the ileal villus morphometry of the 2 species. We concluded that both species can tolerate phytase concentrations much higher than 1,000 phytase units and that these concentrations have further beneficial effects compared with lower phytase concentrations. The work reported here supports the hypothesis that supplementing turkey diets with phytase will need to be considered independently of chicken diets, considering the components in the diets, such that optimal responses can be obtained.

Nutritional approach to restore impaired intestinal barrier function and growth after neonatal stress in rats

OBJECTIVES

Psychological stress during the neonatal period results in intestinal barrier dysfunction and growth alterations later in life. We aimed to restore impaired barrier function and growth rate by a nutritional intervention.

METHODS

Male rat pups (n = 84) were assigned to 1 of 2 rearing conditions from postnatal day (PND) 2 to PND14: S, separated 3 h/d from their mothers, or H, 15 min/d handled controls. From PND15 to PND35, rats received a control diet or a similar diet adapted to contain arachidonic and docosahexaenoic acids, galacto- and fructo-oligosaccharides and Lactobacillus paracasei NCC2461.

RESULTS

Maternal separation had only a minor impact on the measured gut barrier parameters at PND15, whereas it severely affected them at PND35. At this age, intestinal permeability to macromolecules was higher, mucin content in small intestinal tissues was lower and microbiota composition was altered in S compared with H animals. Feeding the adapted diet normalized the intestinal permeability, although it did not restore intestinal mucin content or microbiota. In addition, the adapted diet improved the growth rate recovery of the S animals after weaning and resulted in increased villus length in small intestine.

CONCLUSION

Our results suggest that an adapted diet containing specific long-chain polyunsaturated fatty acids, prebiotics and probiotics can revert the negative imprinting of neonatal stress on both intestinal barrier function and growth.

Box-modeling of 15N/14N in mammals

The 15N/14N signature of animal proteins is now commonly used to understand their physiology and quantify the flows of nutrient in trophic webs. These studies assume that animals are predictably 15N-enriched relative to their food, but the isotopic mechanism which accounts for this enrichment remains unknown. We developed a box model of the nitrogen isotope cycle in mammals in order to predict the 15N/14N ratios of body reservoirs as a function of time, N intake and body mass. Results of modeling show that a combination of kinetic isotope fractionation during the N transfer between amines and equilibrium fractionation related to the reversible conversion of N-amine into ammonia is required to account for the well-established approximately 4 per thousand 15N-enrichment of body proteins relative to the diet. This isotopic enrichment observed in proteins is due to the partial recycling of 15N-enriched urea and the urinary excretion of a fraction of the strongly 15N-depleted ammonia reservoir. For a given body mass and diet delta15N, the isotopic compositions are mainly controlled by the N intake. Increase of the urea turnover combined with a decrease of the N intake lead to calculate a delta15N increase of the proteins, in agreement with the observed increase of collagen delta15N of herbivorous animals with aridity. We further show that the low delta15N collagen values of cave bears cannot be attributed to the dormancy periods as it is commonly thought, but inversely to the hyperphagia behavior. This model highlights the need for experimental investigations performed with large mammals in order to improve our understanding of natural variations of delta15N collagen.

Differential expression and secretion of bovine serum amyloid A3 (SAA3) by mammary epithelial cells stimulated with prolactin or lipopolysaccharide

Serum amyloid A (SAA) proteins were originally identified as prominent acute phase serum reactants synthesized predominately by hepatocytes in response to infection, inflammation and trauma. In this study, we report the differential expression and secretion of serum amyloid A3 (SAA3) by bovine mammary epithelial cells following stimulation with either prolactin (PRL) or lipopolysaccharide (LPS). Reverse transcription-polymerase chain reaction analysis of PRL or LPS induced bovine mammary epithelial cells resulted in the detection of only the mammary-derived Saa3 (M-Saa3) transcript. Two-dimensional immunoblot analyses of colostrum and milk from healthy cows, as well as conditioned medium from PRL or LPS stimulated bovine mammary epithelial cells confirmed the differential production and secretion of M-SAA3 while other SAA isoforms were not detected. These data indicate that the bovine Saa3 gene is regulated differently from the other Saa genes with regard to the site of and stimulus for expression, suggesting an important tissue-specific function for bovine M-SAA3 during lactation and mammary infection.

Staphylococcus aureus lipotechoic acid induces differential expression of bovine serum amyloid A3 (SAA3) by mammary epithelial cells: Implications for early diagnosis of mastitis

Mastitis is one of the most costly diseases of agriculturally important animals and is a common problem for lactating cows. Current methods used to detect clinical and especially subclinical mastitis are either inadequate or problematic. Pathogens such as the gram-positive bacterium Staphylococcus aureus or the gram-negative bacterium Escherichia coli typically cause mastitis. E. coli induces clinical mastitis, whereas, S. aureus causes a subclinical, chronic infection of the mammary gland. In this study we report the differential expression and secretion of mammary-derived serum amyloid A3 (SAA3) by bovine mammary epithelial cells following stimulation with the S. aureus cell wall component, lipotechoic acid (LTA). Two-dimensional immunoblot analyses confirmed that bovine SAA3 is the predominant SAA isoform produced by LTA stimulated mammary epithelial cells. Our previous study showed that bovine SAA3 is also differentially expressed in response to the gram-negative bacterial endotoxin lipopolysaccharide. Collectively, these data indicate that the local production of SAA3 by mammary epithelial cells in response to either gram-positive or gram-negative bacterial components may provide a sensitive indicator for early detection and treatment of mastitis in vivo, minimizing chronic cases of infection, the spread of mastitis to other animals, and economic losses.

Evaluation of Snail Mucin Motifs as Rectal Absorption Enhancer for Insulin in Non-Diabetic Rat Models

The use of snail mucin motifs as rectal absorption enhancer for insulin has been evaluated. The mucin motifs were extracted from the giant African snail Archachatina marginata by differential precipitation with acetone. The mucin motifs were found to have a molecular weight of 5780 Da and an isoelectric point of 3.4. At the concentrations evaluated, the mucin exhibited rectal absorption enhancing property for the administration of insulin in rats. The % basal blood glucose level of the rats that received the batch of suppositories containing no mucin were consistently above 100% except at the ninetieth minute when it came down slightly to 97.2%. Rats dosed with the batch containing 7%w/w suppositories showed the greatest blood glucose reduction with mean % basal blood glucose concentration of 61.2%. Batches of the suppository containing 5% and 7% mucin showed more marked and consistent lowering in blood glucose concentration than the other batches containing lower amounts of the rectal absorption enhancer. The batch with 7% mucin reduced the basal glucose level to 44% within 2 h of administration of the glycero-gelatin suppository loaded mucin.

Splanchnic bed metabolism of glucose in preterm neonates

BACKGROUND

Glucose is a major oxidative substrate for intestinal energy generation in neonatal animals; however, few data in preterm infants are available. Early administration of enteral nutrition, including glucose, may be an effective strategy to support intestinal adaptation to extrauterine life in preterm neonates.

OBJECTIVE

The purpose of the present study was to quantify the first-pass uptake and oxidation of glucose by the splanchnic tissues (intestine and liver) in human neonates.

DESIGN

Eight preterm infants [birth weight ( +/- SD): 1.19 +/- 0.22 kg, gestational age: 29 +/- 1 wk] were studied while they received 2 different enteral intakes (A: 40% enteral, 60% parenteral, total glucose intake = 7.5 +/- 0.5 mg. kg(-1). min(-1), and B: 100% enteral, total glucose intake = 7.8 +/- 0.4 mg. kg(-1). min(-1)). Splanchnic and whole-body glucose kinetics were measured by use of dual-tracer techniques.

RESULTS

During both feeding periods, approximately one-third of dietary glucose intake was utilized during the first pass by the splanchnic tissues. More than three-quarters of this utilized glucose was oxidized in both periods (79 +/- 36% with A and 84 +/- 45% with B). Whole-body glucose oxidation was substantial under both circumstances: 72 +/- 5% and 77% +/- 6% of the glucose flux was oxidized during partial (A) and full (B) enteral feeding, respectively.

CONCLUSIONS

Approximately one-third of dietary glucose is utilized during the first pass by the splanchnic tissues, irrespective of the dietary intake. Most of the utilized glucose is used for energy generation.

Effect of Diet on Mucin Kinetics and Composition: Nutrition and Health Implications

The mucus gel covering the gut epithelium is in dynamic balance between synthesis and secretion of mucin from goblet cells and proteolytic and physical erosion that releases mucin into the lumen. In the lumen, mucin is partially protected from proteolysis by carbohydrate chains, and it contributes to endogenous protein reaching the ileum. Dietary components modulate the contribution of mucin to endogenous protein components and their qualitative composition. In addition, mucin plays a key role in gastrointestinal protection in association with the microflora. In this review, we will attempt to evaluate the consequences of dietary manipulation of mucin on gut health.

The conserved TFLK motif of mammary-associated serum amyloid A3 is responsible for up-regulation of intestinal MUC3 mucin expression in vitro

In various mammalian species, an isoform of serum amyloid A is secreted at high concentrations into colostrum. A conserved four-amino-acid motif (TFLK) is contained within the first eight N-terminal amino acid residues of this mammary-associated serum amyloid A isoform 3 (M-SAA3). Peptides derived from the bovine N-terminal amino acid sequence of M-SAA3 were produced and added to cell culture medium of HT29 cells to study the effects on intestinal mucin gene expression. HT29 cells were grown to enhance expression of either MUC2 or MUC3 intestinal mucins. After incubation, total RNA was isolated for Northern blot analyses using MUC2 or MUC3 mucin cDNA probes. Signals were detected by autoradiography with mRNA levels expressed relative to 28S rRNA. The 10-mer peptides containing the intact TFLK-motif or a TFLK 4-mer peptide increased MUC3 mRNA expression compared with control cells (p < 0.05). There was no effect of these peptides on MUC2 mRNA expression. Cells that were incubated with 10-mer N-terminal derived peptides containing a scrambled TFLK motif, with all 10 amino acid residues scrambled or derived from a C-terminal region of M-SAA3, did not show increased MUC3 expression. Inhibition of enteropathogenic Escherichia coli strain E2348/69 adhesion to HT29 cells grown to enhance MUC3 expression was reduced by a similar amount when either peptides containing the intact TFLK motif or probiotic microbes were added to cell culture medium compared with control cells. M-SAA3 is a bioactive peptide secreted into colostrums that can up-regulate mucin expression and thereby may enhance innate protective mechanisms that limit access of deleterious microbes to intestinal mucosal epithelial cells in the postparturition period.

Elevated extrahepatic expression and secretion of mammary-associated serum amyloid A 3 (M-SAA3) into colostrum

Mammary-associated serum amyloid A 3 (M-SAA3) was secreted at highly elevated levels in bovine, equine and ovine colostrum and found at lower levels in milk 4 days postparturition. N-terminal sequencing of the mature M-SAA3 protein from all the three species revealed a conserved four amino acid motif (TFLK) within the first eight residues. This motif has not been reported to be present in any of the hepatically-produced acute phase SAA (A-SAA) isoforms. Cloning of the bovine M-Saa3 cDNA from mammary gland epithelial cells revealed an open reading frame that encoded a precursor protein of 131 amino acids which included an 18 amino acid signal peptide. The predicted 113 residue mature M-SAA3 protein had a theoretical molecular mass of 12,826Da that corresponded with the observed 12.8kDa molecular mass obtained for M-SAA3 in immunoblot analysis. The high abundance of this extrahepatically produced SAA3 isoform in the colostrum of healthy animals suggests that M-SAA3 may play an important functional role associated with newborn adaptation to extrauterine life and possibly mammary tissue remodeling.

Influence of dietary protein level and origin on the flow of mucin along the small intestine of the preruminant calf

The objective of this study was to investigate the effect of the dietary crude protein (CP) content and origin on the flow of mucin protein along the small intestine of the preruminant calf. Diets contained 1, 10, 20 and 28% of CP supplied by skim milk powder (SMP) in experiment 1. Diets differed by the nature of protein [soybean protein concentrate (SPC), partially hydrolyzed soybean protein isolate (HSPI) or potato protein concentrate (PPC)] in experiment 2. Duodenal, jejunal, and ileal digesta were collected from calves fitted with simple cannulae and continuously infused the milk replacers into the abomasum. In experiment 1, the basal flow of mucin protein was 1.1, 1.8, and 4.0 g/kg of dry matter intake at the duodenum, jejunum, and ileum, respectively. Mucin protein contributed to 19 and 40% of ileal loss of CP and lysine, respectively. When dietary CP rose from 1 to 28%, the flow of mucin protein increased at the duodenum (+300%). In experiment 2, the flow of mucin protein increased by 70% at the duodenum and at the jejunum when SMP was partially replaced by SPC and HSPI. With PPC, this flow increased at the duodenum (+24%) and ileum (+52%). These data demonstrate the importance of mucin as a source of endogenous nitrogen and the impact of dietary protein content and origin on this flow.