Effects of a diet high in resistant starch on fermentation end-products of protein and mucin secretion in the colons of pigs

The interactivity of sources and dietary levels of resistant starches - impact on growth performance, starch, and nutrient digestibility, digesta oligosaccharides profile, cecal microbial metabolites, and indicators of gut health in broiler chickens

In a 21-d study, 480 Cobb 500 (off-sex) male broiler chicks were used to investigate the effects of feeding different sources and levels of resistant starches (RS) on growth performance, nutrient and energy utilization, and intestinal health in broiler chickens. The birds were allocated to 10 dietary treatments in a 3 × 3 + 1 factorial arrangement. The factors were 3 RS-sources (RSS): banana starch (BS), raw potato starch (RPS), and high-amylose corn starch (HCS); each at 3 levels (RSL) 25, 50, or 100 g/kg plus a corn-soybean meal control diet. Birds and feed were weighed on d 0, 8, and 21. On d 21, samples of jejunal tissue and digesta were collected for chemical analysis. Data were analyzed using the mixed model procedure of JMP with factor levels nested with the control. In the 0 to 21 phase, the birds fed the RPS diets had higher (P = 0.011) FI than those fed HCS or control diets, and FCR was greater (P = 0.030) in birds that received BS diets than in other diets. RSS × RSL was significant (P < 0.05) for total tract nutrient retention, AME, and AMEn on d 21. The starch digestibility was higher (P < 0.001) in birds that received the control diet than in RS diets, and decreased as RS levels increased, except for HCS. The apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) were higher (P < 0.001) in birds fed 100 g/kg HCS diet, with both decreasing with increasing levels of BS and RPS, except for HCS. Relative ileal oligosaccharides profile showed significant (P < 0.05) RSS × RSL with a higher relative abundance of Hex(3) (P = 0.01) and Pent(3) (P = 0.001) in HCS diets. In conclusion, RS may influence gut health and growth performance in broiler chickens through modulation of cecal SCFA and nutrient digestion, but these depend largely on the botanical origin and concentrations of individual RS.

Rumen and hindgut microbiome regulate average daily gain of preweaning Holstein heifer calves in different ways

BACKGROUND

The average daily gain (ADG) of preweaning calves significantly influences their adult productivity and reproductive performance. Gastrointestinal microbes are known to exert an impact on host phenotypes, including ADG. The aim of this study was to investigate the mechanisms by which gastrointestinal microbiome regulate ADG in preweaning calves and to further validate them by isolating ADG-associated rumen microbes in vitro.

RESULTS

Sixteen Holstein heifer calves were selected from a cohort with 106 calves and divided into higher ADG (HADG; n = 8) and lower ADG (LADG; n = 8) groups. On the day of weaning, samples of rumen contents, hindgut contents, and plasma were collected for rumen metagenomics, rumen metabolomics, hindgut metagenomics, hindgut metabolomics, and plasma metabolomics analyses. Subsequently, rumen contents of preweaning Holstein heifer calves from the same dairy farm were collected to isolate ADG-associated rumen microbes. The results showed that the rumen microbes, including Pyramidobacter sp. C12-8, Pyramidobacter sp. CG50-2, Pyramidobacter porci, unclassified_g_Pyramidobacter, Pyramidobacter piscolens, and Acidaminococcus fermentans, were enriched in the rumen of HADG calves (LDA > 2, P < 0.05). Enrichment of these microbes in HADG calves' rumen promoted carbohydrate degradation and volatile fatty acid production, increasing proportion of butyrate in the rumen and ultimately contributing to higher preweaning ADG in calves (P < 0.05). The presence of active carbohydrate degradation in the rumen was further suggested by the negative correlation of the rumen microbes P. piscolens, P. sp. C12-8 and unclassified_g_Pyramidobacter with the rumen metabolites D-fructose (R <  - 0.50, P < 0.05). Widespread positive correlations were observed between rumen microbes (such as P. piscolens, P. porci, and A. fermentans) and beneficial plasma metabolites (such as 1-pyrroline-5-carboxylic acid and 4-fluoro-L-phenylalanine), which were subsequently positively associated with the growth rate of HADG calves (R > 0.50, P < 0.05). We succeeded in isolating a strain of A. fermentans from the rumen contents of preweaning calves and named it Acidaminococcus fermentans P41. The in vitro cultivation revealed its capability to produce butyrate. In vitro fermentation experiments demonstrated that the addition of A. fermentans P41 significantly increased the proportion of butyrate in the rumen fluid (P < 0.05). These results further validated our findings. The relative abundance of Bifidobacterium pseudolongum in the hindgut of HADG calves was negatively correlated with hindgut 4-hydroxyglucobrassicin levels, which were positively correlated with plasma 4-hydroxyglucobrassicin levels, and plasma 4-hydroxyglucobrassicin levels were positively correlated with ADG (P < 0.05).

CONCLUSIONS

This study's findings unveil that rumen and hindgut microbes play distinctive roles in regulating the preweaning ADG of Holstein heifer calves. Additionally, the successful isolation of A. fermentans P41 not only validated our findings but also provided a valuable strain resource for modulating rumen microbes in preweaning calves. Video Abstract.

Effects of dietary crude protein content and resistant starch supplementation on growth performance, intestinal histomorphology and microbial metabolites in weaned pigs

A 4-week study was conducted to evaluate the effects of dietary crude protein (CP) content and resistant starch (RS) supplementation on growth performance, intestinal histomorphology and microbial metabolites of weaned pigs. A total of 96 pigs (7.06 ± 0.45 kg body weight) were assigned to 1 of 4 diets in a randomised complete block design involving a 2 (CP levels) × 2 (without or with RS) factorial arrangement to give 8 replicate pens and 3 pigs per pen. Body weight and feed disappearance were recorded weekly, and the faecal consistency score was determined every morning. Blood was sampled on days 1, 14 and 28 from one pig per pen, and the same pig was euthanised on day 28 to collect ileal tissue and ileal and colon digesta. Data were analysed using the MIXED procedure of SAS. The average daily gain and gain:feed ratio were lower (p < 0.05) in pigs fed low crude protein (LCP) diets compared to those fed high CP (HCP) diets during week 3 and overall period. The analysed Lys, Met+Cys and Thr in feed were lower than calculated values, particularly in LCP diets, which may have affected performance. Pigs fed the LCP diets had longer (p < 0.05) ileal villi and higher villus height to crypt depth ratios than those fed the HCP diets, and RS supplementation increased (p < 0.05) ileal villus height. Interactions (p < 0.05) between dietary CP content and RS inclusion were observed for short-chain fatty acid concentration in the ileum and colon in phase 2. There was no difference in propionic acid (ileum) or butyric acid (colon) concentrations among pigs fed HCP diets, however, the butyric acid concentration increased in pigs fed the LCP diet when supplemented with RS. Reducing dietary CP lowered (p < 0.05) faecal score, plasma urea nitrogen and digesta ammonia content. Overall, feeding LCP diets reduced growth performance but improved gut morphology in weaned pigs. Feeding the LCP diet with RS supplementation modulated concentrations of ileal propionic acid and colonic butyric acid in weaned pigs.

Comparison between Organic and Inorganic Zinc Forms and Their Combinations with Various Dietary Fibers in Respect of the Effects on Electrolyte Concentrations and Mucosa in the Large Intestine of Pigs

This study aimed to determine the effects of Zn sources, used with potato fiber (PF) or lignocellulose (LC), on electrolyte concentration and the mucus layer in the large intestine of pigs. The experiment involved 24 barrows with an initial body weight of 10.8 ± 0.82 kg, divided into four groups fed the following diets: LC and ZnSO4, LC and Zn glycinate (ZnGly), PF and ZnSO4, or PF and ZnGly. Fiber supplements provided 10 g crude fiber/kg diet, while Zn additives introduced 120 mg Zn/kg diet. After four weeks of feeding, the pigs were sacrificed and digesta and tissue samples were taken from the cecum and colon. PF increased the water content and decreased the phosphorus concentration in the large intestine in comparison with LC. PF also increased calcium, iron, and chloride concentrations in the descending colon. Mucus layer thickness and histological parameters of the large intestine were not affected. ZnGly diets increased MUC12 expression in the cecum as compared to the LC-ZnSO4 group. In the ascending colon, the PF-ZnGly diet increased MUC5AC expression, while both PF groups had greater MUC20 expression in comparison with the LC-ZnSO4 group. In the transverse colon, the LC-ZnGly group and both PF groups had higher MUC5AC expression in comparison with the LC-ZnSO4 group, and both ZnGly groups had higher MUC20 expression than ZnSO4 groups. PF and ZnGly increased MUC4 and MUC5AC expression in the descending colon. PF and ZnGly may exert a beneficial effect on colon health in pigs by upregulating the expression of the MUC5AC and MUC20 genes and are more effective than LC and ZnSO4.

Possible role of tryptophan metabolism along the microbiota-gut-brain axis on cognitive & behavioral aspects in Phenylketonuria

Cognitive and psychiatric disorders are well documented across the lifetime of patients with inborn errors of metabolism (IEMs). Gut microbiota impacts behavior and cognitive functions through the gut-brain axis (GBA). According to recent research, a broad spectrum of GBA disorders may be influenced by a perturbed Tryptophan (Trp) metabolism and are associated with alterations in composition or function of the gut microbiota. Furthermore, early-life diets may influence children's neurodevelopment and cognitive deficits in adulthood. In Phenylketonuria (PKU), since the main therapeutic intervention is based on a life-long restrictive diet, important alterations of gut microbiota have been observed. Studies on PKU highlight the impact of alterations of gut microbiota on the central nervous system (CNS), also investigating the involvement of metabolic pathways, such as Trp and kynurenine (KYN) metabolisms, involved in numerous neurodegenerative disorders. An alteration of Trp metabolism with an imbalance of the KYN pathway towards the production of neurotoxic metabolites implicated in numerous neurodegenerative and inflammatory diseases has been observed in PKU patients supplemented with Phe-free amino acid medical foods (AA-MF). The present review investigates the possible link between gut microbiota and the brain in IEMs, focusing on Trp metabolism in PKU. Considering the evidence collected, cognitive and behavioral well-being should always be monitored in routine IEMs clinical management. Further studies are required to evaluate the possible impact of Trp metabolism, through gut microbiota, on cognitive and behavioral functions in IEMs, to identify innovative dietetic strategies and improve quality of life and mental health of these patients.

Type 2-resistant starch and Lactiplantibacillus plantarum NCIMB 8826 result in additive and interactive effects in diet-induced obese mice

Little is known about how combining a probiotic with prebiotic dietary fiber affects the ability of either biotic to improve health. We hypothesized that prebiotic, high-amylose maize type 2-resistant starch (RS) together with probiotic Lactiplantibacillus plantarum NCIMB8826 (LP) as a complementary synbiotic results in additive effects on the gut microbiota in diet-induced obese mice and other body sites. Diet-induced obese C57BL/6J male mice were fed a high-fat diet adjusted to contain RS (20% by weight), LP (109 cells every 48 hours), or both (RS+LP) for 6 weeks. As found for mice fed RS, cecal bacterial alpha diversity was significantly reduced in mice given RS+LP compared with those fed LP and high-fat controls. Similarly, both RS+LP and RS also conferred lower quantities of cecal butyrate and serum histidine and higher ileal TLR2 transcript levels and adipose tissue interleukin-6 protein. As found for mice fed LP, RS+LP-fed mice had higher colonic tissue TH17 cytokines, reduced epididymal fat immune and oxidative stress responses, reduced serum carnitine levels, and increased transcript quantities of hepatic carnitine palmitoyl transferase 1α. Notably, compared with RS and LP consumed separately, there were also synergistic increases in colonic glucose and hepatic amino acids as well antagonistic effects of LP on RS-mediated increases in serum adiponectin and urinary toxin levels. Our findings show that it is not possible to fully predict outcomes of synbiotic applications based on findings of the probiotic or the prebiotic tested separately; therefore, studies should be conducted to test new synbiotic formulations.

A Low-Protein, High-Carbohydrate Diet Exerts a Neuroprotective Effect on Mice with 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-Induced Parkinson's Disease by Regulating the Microbiota-Metabolite-Brain Axis and Fibroblast Growth Factor 21

Parkinson's disease (PD) is closely linked to lifestyle factors, particularly dietary patterns, which have attracted interest as potential disease-modifying factors. Eating a low-protein, high-carbohydrate (LPHC) diet is a promising dietary intervention against brain aging; however, its protective effect on PD remains elusive. Here, we found that an LPHC diet ameliorated 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP)-induced motor deficits, decreased dopaminergic neuronal death, and increased the levels of striatal dopamine, serotonin, and their metabolites in PD mice. Levels of fibroblast growth factor 21 (FGF-21), a member of the fibroblast growth factor family, were elevated in PD mice following LPHC treatment. Furthermore, the administration of FGF-21 exerted a protective effect on MPTP-induced PC12 cells, similar to the effect of an LPHC diet in MPTP-induced mice. Sequencing of the 16S rDNA from fecal microbiota revealed that an LPHC diet normalized the gut bacterial composition imbalance in PD mice, as evidenced by the increased abundance of the genera Bifidobacterium, Ileibacterium, Turicibacter, and Blautia and decreased abundance of Bilophila, Alistipes, and Bacteroides. PICRUSt-predicted fecal microbiome function revealed that an LPHC diet suppressed lipopolysaccharide biosynthesis and the citrate cycle (TCA cycle), biosynthesis of ubiquinone and other terpenoid-quinones, and oxidative phosphorylation pathways caused by MPTP, and enhanced the biosynthesis of amino acids, carbohydrate metabolism, and biosynthesis of other secondary metabolites. A nonmetabolomic analysis of the serum and feces showed that an LPHC diet significantly increased the levels of aromatic amino acids (AAAs), including tryptophan, tyrosine, and phenylalanine. In addition, an LPHC diet elevated the serum concentrations of bile acids (BAs), particularly tauroursodeoxycholic acid (TUDCA) and taurine. Collectively, our current findings point to the potential mechanism of administering an LPHC diet in attenuating movement impairments in MPTP-induced PD mice, with AAAs, microbial metabolites (TUDCA and taurine), and FGF-21 as key mediators along the gut-microbiota-brain axis.

Eating Quality of Pork from Entire Male Pigs after Dietary Supplementation with Hydrolysable Tannins

Boar taint is an unpleasant odour and flavour released during heat treatment of pork from uncastrated male pigs. The two main compounds responsible for boar taint are androstenone and skatole. Androstenone is a steroid hormone formed in the testis during sexual maturity. Skatole is a product of microbial degradation of the amino acid tryptophan in the hindgut of pigs. Both of these compounds are lipophilic, which means that they can be deposited in adipose tissue. Several studies have reported heritability estimates for their deposition from medium (skatole) to high magnitudes (androstenone). In addition to efforts to influence boar taint through genetic selection, much attention has also been paid to reducing its incidence using various feeding strategies. From this point of view, research has focused especially on the reduction in skatole content by supplementation of feed additives into the nutrition of entire male pigs. Promising results have been achieved using hydrolysable tannins in the diet. To date, most studies have investigated the effects of tannins on the production and accumulation of skatole in adipose tissue, intestinal microbiota, growth rate, carcasses and pork quality. Thus, the objective of this study was, in addition to determining the effects of tannins on androstenone and skatole accumulation, to assess the effects of tannins on the sensory traits of meat from entire males. The experiment was performed on 80 young boars-progeny of several hybrid sire lines. Animals were randomly assigned to one control and four experimental groups (each numbering 16). The control group (T0) received a standard diet without any tannin supplementation. Experimental groups were supplemented with 1% (T1), 2% (T2), 3% (T3) or 4% (T4) SCWE (sweet chestnut wood extract) rich in hydrolysable tannins (Farmatan). Pigs received this supplement for 40 days prior to slaughter. Subsequently, the pigs were slaughtered, and sensory analysis was applied to evaluate the odour, flavour, tenderness and juiciness of the pork. The results showed a significant effect of tannins on skatole accumulation in adipose tissue (p = 0.052-0.055). The odour and flavour of the pork were not affected by tannins. However, juiciness and tenderness were reduced by higher tannin supplementation (T3-T4) compared to the controls (p < 0.05), but these results were sex-dependent (in favour of men compared to women). Generally, women rated tenderness and juiciness worse than men regardless of the type of diet.

Effect of feeding raw potato starch on the composition dynamics of the piglet intestinal microbiome

OBJECTIVE

Raw potato starch (RPS) is resistant to digestion, escapes absorption, and is metabolized by intestinal microflora in the large intestine and acts as their energy source. In this study, we compared the effect of different concentrations of RPS on the intestinal bacterial community of weaned piglets.

METHODS

Male weaned piglets (25-days-old, 7.03±0.49 kg) were either fed a corn/soybean-based control diet (CON, n = 6) or two treatment diets supplemented with 5% RPS (RPS5, n = 4) or 10% RPS (RPS10, n = 4) for 20 days and their fecal samples were collected. The day 0 and 20 samples were analyzed using a 16S rRNA gene sequencing technology, followed by total genomic DNA extraction, library construction, and high-throughput sequencing. After statistical analysis, five phyla and 45 genera accounting for over 0.5% of the reads in any of the three groups were further analyzed. Furthermore, short-chain fatty acids (SCFAs) in the day 20 fecal samples were analyzed using gas chromatography.

RESULTS

Significant changes were not observed in the bacterial composition at the phylum level even after 20 d post feeding (dpf); however, the abundance of Intestinimonas and Barnesiella decreased in both RPS treatment groups compared to the CON group. Consumption of 5% RPS increased the abundance of Roseburia (p<0.05) and decreased the abundance of Clostridium (p<0.01) and Mediterraneibacter (p< 0.05). In contrast, consumption of 10% RPS increased the abundance of Olsenella (p<0.05) and decreased the abundance of Campylobacter (p<0.05), Kineothrix (p<0.05), Paraprevotella (p<0.05), and Vallitalea (p<0.05). Additionally, acetate (p<0.01), butyrate (p<0.05), valerate (p = 0.01), and total SCFAs (p = 0.01) were upregulated in the RPS5 treatment group.

CONCLUSION

Feeding 5% RPS altered bacterial community composition and promoted gut health in weaned piglets. Thus, resistant starch as a feed additive may prevent diarrhea in piglets during weaning.

Impact of Lycium barbarum arabinogalactan on the fecal metabolome in a DSS-induced chronic colitis mouse model

Ulcerative colitis (UC) is often accompanied by the dysbiosis of gut microbiota and metabolism. Our previous study indicated that arabinogalactan from Lycium barbarum (LBP-3) could markedly attenuate the symptoms of chronic UC in mice by modulating the structure of gut microbiota. This study explored the impact of LBP-3 on the fecal metabolomic profiling of the same cohort of mice by HPLC-TripleTOF/MS. Untargeted metabolomic analyses indicated that supplementation with LBP-3 markedly reversed 18 of the 48 differential metabolites (mainly belonging to amino acids and organic acids) disturbed by DSS. Targeted metabolomics revealed that the lower levels of tryptophan, lysine, diiodothyronine, kynurenine, and betaine and higher levels of phenylalanine, leucine, glutamine, isoleucine, homoserine, (S)-2-hydroxyglutarate, 2-isopropylmalic acid, ascorbic acid, gluconic acid, and taurine, which were caused by DSS induction, were reversed by LBP-3 treatment. In addition, pathway analysis showed that the pentose phosphate pathway, phenylalanine metabolism, ascorbate and aldarate metabolism, and phenylalanine, tyrosine and tryptophan biosynthesis were strongly affected by LBP-3. More importantly, the above amino acids, organic acids, and metabolic pathways changed by LBP-3 were correlated with the abundance of gut microbiota such as Turicibacter, Lactobacillus, Parasutterella, Odoribacter, Veillonella, Faecalibacterium, and Ruminococcaceae. This study advances our understanding of the interaction between the microbiome and metabolomics in DSS-induced chronic colitis after LBP-3 treatment.

Resistant Potato Starch Alters the Cecal Microbiome and Gene Expression in Mice Fed a Western Diet Based on NHANES Data

Several studies indicate that the four major types of resistant starch (RS1-4) are fermented in the cecum and colon to produce short-chain fatty acids (SCFAs) and can alter the microbiome and host physiology. However, nearly all these studies were conducted in rodents fed with a diet that does not approximate what is typically consumed by humans. To address this, mice were fed a Total Western Diet (TWD) based on National Health and Nutrition Examination Survey (NHANES) data that mimics the macro and micronutrient composition of a typical American diet for 6 weeks and then supplemented with 0, 2, 5, or 10% of the RS2, resistant potato starch (RPS), for an additional 3 weeks. The cecal microbiome was analyzed by 16S sequencing. The alpha-diversity of the microbiome decreased with increasing consumption of RPS while a beta-diversity plot showed four discreet groupings based on the RPS level in the diet. The relative abundance of various genera was altered by feeding increasing levels of RPS. In particular, the genus Lachnospiraceae NK4A136 group was markedly increased. Cecal, proximal, and distal colon tissue mRNA abundance was analyzed by RNASeq. The cecal mRNA abundance principal component analysis showed clear segregation of the four dietary groups whose separation decreased in the proximal and distal colon. Differential expression of the genes was highest in the cecum, but substantially decreased in the proximal colon (PC) and distal colon (DC). Most differentially expressed genes were unique to each tissue with little overlap in between. The pattern of the observed gene expression suggests that RPS, likely through metabolic changes secondary to differences in microbial composition, appears to prime the host to respond to a range of pathogens, including viruses, bacteria, and parasites. In summary, consumption of dietary RPS led to significant changes to the microbiome and gene expression in the cecum and to a lesser extent in the proximal and distal colon.

Potential Roles of Enterochromaffin Cells in Early Life Stress-Induced Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, also known as disorders of the gut–brain interaction; however, the pathophysiology of IBS remains unclear. Early life stress (ELS) is one of the most common risk factors for IBS development. However, the molecular mechanisms by which ELS induces IBS remain unclear. Enterochromaffin cells (ECs), as a prime source of peripheral serotonin (5-HT), play a pivotal role in intestinal motility, secretion, proinflammatory and anti-inflammatory effects, and visceral sensation. ECs can sense various stimuli and microbiota metabolites such as short-chain fatty acids (SCFAs) and secondary bile acids. ECs can sense the luminal environment and transmit signals to the brain via exogenous vagal and spinal nerve afferents. Increasing evidence suggests that an ECs-5-HT signaling imbalance plays a crucial role in the pathogenesis of ELS-induced IBS. A recent study using a maternal separation (MS) animal model mimicking ELS showed that MS induced expansion of intestinal stem cells and their differentiation toward secretory lineages, including ECs, leading to ECs hyperplasia, increased 5-HT production, and visceral hyperalgesia. This suggests that ELS-induced IBS may be associated with increased ECs-5-HT signaling. Furthermore, ECs are closely related to corticotropin-releasing hormone, mast cells, neuron growth factor, bile acids, and SCFAs, all of which contribute to the pathogenesis of IBS. Collectively, ECs may play a role in the pathogenesis of ELS-induced IBS. Therefore, this review summarizes the physiological function of ECs and focuses on their potential role in the pathogenesis of IBS based on clinical and pre-clinical evidence.

The Remodeling Effects of High-Concentrate Diets on Microbial Composition and Function in the Hindgut of Dairy Cows

At present, research on high-concentrate (HC) diets mostly focused on the rumen, and there is a paucity of information on the hindgut microbiota of dairy cows. In the present study, a 2 × 2 crossover design with four healthy Holstein cows was used, and the metagenomics approach was adopted to reveal the remodeling effects of HC diets on hindgut microbiota and their metabolic functions. Results showed that, compared with the low-concentrate (LC) diets, HC diets have markedly decreased (p < 0.05) the abundance of cellulolytic bacteria (such as Fibrobacter, Ruminococcus, and Ruminiclostridium) and methanogens (such as Methanobrevibacter, Methanosarcina, and Methanosphaera); and correspondingly, HC diets have significantly reduced (p < 0.05) the abundance of carbohydrate-active enzymes (CAZy) related to hemicellulases (GH10, GH11, and GH54) and cellulases (GH1, GH44, and GH45) and increased the abundance of one oligosaccharide-degrading enzyme (GH32). Furthermore, 62 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of hindgut microbiota were affected (p < 0.05) by different dietary treatments, and the major pathways altered by HC diets were “Methane metabolism” (enriched in the LC group), “Lipid metabolism” (enriched in the HC group), and several sub-pathways in “Amino acid metabolism” (such as Phenylalanine metabolism, and Phenylalanine, tyrosine, and tryptophan biosynthesis). Also, the microbial genes involved in the pathways “Methane metabolism” (except 1 gene), “Tryptophan metabolism”, and “Phenylalanine metabolism” were all decreased (p < 0.05) in the present study. These findings suggested that HC diets caused the remodeling of hindgut microbiota and its potential functions, and these results may benefit in gaining a deeper understanding of the impact of HC diets on the hindgut microbiota of dairy cows.

Resistant starch: Implications of dietary inclusion on gut health and growth in pigs: a review

Starch from cereal grains, pulse grains, and tubers is a major energy substrate in swine rations constituting up to 55% of the diet. In pigs, starch digestion is initiated by salivary and then pancreatic α-amylase, and has as final step the digestion of disaccharides by the brush-border enzymes in the small intestine that produce monosaccharides (glucose) for absorption. Resistant starch (RS) is the proportion of starch that escapes the enzymatic digestion and absorption in the small intestine. The undigested starch reaches the distal small intestine and hindgut for microbial fermentation, which produces short-chain fatty acids (SCFA) for absorption. SCFA in turn, influence microbial ecology and gut health of pigs. These fermentative metabolites exert their benefits on gut health through promoting growth and proliferation of enterocytes, maintenance of intestinal integrity and thus immunity, and modulation of the microbial community in part by suppressing the growth of pathogenic bacteria while selectively enhancing beneficial microbes. Thus, RS has the potential to confer prebiotic effects and may contribute to the improvement of intestinal health in pigs during the post-weaning period. Despite these benefits to the well-being of pigs, RS has a contradictory effect due to lower energetic efficiency of fermented vs. digested starch absorption products. The varying amount and type of RS interact differently with the digestion process along the gastrointestinal tract affecting its energy efficiency and host physiological responses including feed intake, energy metabolism, and feed efficiency. Results of research indicate that the use of RS as prebiotic may improve gut health and thereby, reduce the incidence of post-weaning diarrhea (PWD) and associated mortality. This review summarizes our current knowledge on the effects of RS on microbial ecology, gut health and growth performance in pigs.

Can Hydrolysable Tannins in Diet of Entire Male Pigs Affect Carcass, Pork Quality Traits, Amino and Fatty Acid Profiles, and Boar Taint, Skatole and Androstenone Levels?

The slaughtering of entire males increases the probability of incidence of tainted pork due to the presence two main compounds-androstenone and skatole. If a surgical castration of young entire male pigs is stopped in the EU countries, fattening of boars is likely to become one of the most commonly used systems in pig farming. Since skatole production and accumulation in fat tissue can be controlled by dietary approaches, several studies have investigated various feed additives to reduce this compound of boar taint. Ones of the most promising is tannins. The aim of this study was to determine the effect of different dietary tannin level supplementation on carcass, pork quality, chemical, amino and fatty acid composition. as well as perception of boar taint and accumulation of skatole and androstenone in adipose tissue. Eighty entire males were randomly distributed to control (T0) and four experimental groups. Control pigs received standard feed mixture (16.8% CP, 13.9 MJ ME) without any tannin supplementation. Experimental pigs received the same diet with administration of 1% (T1), 2% (T2), 3% (T3) and 4% (T4)-sweet chestnut extract rich in hydrolysable tannins for 40 days (from average live weight of 80 kg until slaughter at average weight 122.28 kg ± 5.63 kg). Dietary tannins supplementation did not show any significant effect on chemical composition, cholesterol content, and amino acid composition of muscle as well as fatty acid composition and androstenone accumulation in adipose tissue. A slight or small effect was observed on carcass and meat quality, respectively. Pigs in groups T4 and/or T3-T4 had higher electrical conductivity in semimembranosus muscle and cooking loss value compared to T1, T2 or T0, T1, and T2 groups (p < 0.05). Tannins in the pig's diet greatly affected fatty acid profile in meat of entire males. The highest tannin levels (4%) increased concentrations of lauric, myristic, vaccenic, linoleic, total PUFA, and n-6 PUFA in muscle compared to the control. Similar results were found in group T3 except for vaccenic, linoleic, and total PUFA. On the contrary, concentrations of heptadecanoic and oleic acids in groups T3 and T4 were lower than those in T1 and T2 groups. Perception of boar taint using "hot iron" method (insertion a hot iron tip of soldering iron into adipose tissue) tended to decrease in T2 group compared with control. Skatole accumulation in fat tissue was reduced in groups T2-T4 at significance level (p = 0.052-0.055) compared to the control pigs. In summary, tannins supplementation had no effect on chemical and amino acid composition as well as fatty acid profile in adipose tissue, and only slight on carcass value. However, 4% concentration of tannins significantly increased content of some fatty acids compared to control group.

Intestinal Health and Threonine Requirement of Growing Pigs Fed Diets Containing High Dietary Fibre and Fermentable Protein

Simple Summary

Dietary components, such as fibre and protein, have significant impacts on nutrient requirements and intestinal health in pigs. The objectives of this study were to investigate the interactive effects of dietary fibre and fermentable protein on threonine requirement for protein deposition in growing pigs and to determine how these factors affect markers of intestinal health. In this study we used the nitrogen-balance approach to study the influence of high protein diets combined with high fibre on threonine requirement for protein deposition. We further used gene expression, fermentation metabolites (short and branched chain fatty acid concentration), and serum antioxidant status in these pigs as markers of intestinal health and function. We demonstrate that high fibre will indeed increase threonine requirement for protein deposition but can mitigate the negative effects of fermentable protein metabolites on intestinal health. These results will have implications for the development of dietary strategies to improve growth and overall health in pigs, including adjustments to dietary fibre, protein, and amino acid content that maximize pig growth, nutrient utilization, and intestinal health.

Abstract

Dietary fibre (DF) and fermentable crude protein (fCP) are dietary factors which affect nutrient utilization and intestinal health in pigs. A nitrogen (N)-balance study was conducted to determine the impact of DF and fCP on threonine (Thr) requirement for protein deposition (PD) and indicators of intestinal health. A total of 160 growing pigs (25 kg) were randomly assigned to 1 of 20 dietary treatments in a 2 × 2 × 5 factorial arrangement in a randomized complete block design with dietary fibre (low (LF) or high fibre (HF)], fCP [low (LfCP) or high fCP (HfCP)) and Thr (0.52, 0.60, 0.68, 0.76, or 0.82% standardized ileal digestible) as factors. Then, 4-day total urine and fecal collection was conducted, and pigs were euthanized for intestinal tissue and digesta sampling. Feeding high DF, regardless of fCP content, increased Thr requirement for PD (p < 0.05). High fCP, regardless of DF content, reduced Thr requirement for PD. Serum antioxidant capacity increased as dietary Thr level increased (p < 0.05). Cecal digesta short-chain fatty acids (SCFA) increased (p < 0.05) with HF and branched-chain fatty acids (BCFA) increased with HfCP and reduced with HF (p < 0.05). HfCP reduced (p < 0.05) mucin-2 (MUC2) expression in the colon of the HF but not the LF fed pigs and HF increased MUC2 in the LfCP but not the HfCP fed pigs. Feeding HF diet increased (p < 0.05) expression of zonula occludens-1 in the LfCP with no effect on HfCP fed pigs. Ammonia concentration in both cecum and colon increased (p < 0.05) in the HfCP fed pigs. Overall, high DF reduced the negative impact of HfCP on intestinal health, as indicated by alterations in SCFA and BCFA production and gut barrier gene expression. While increased dietary Thr content is required for PD in pigs fed high DF, feeding high fCP reduced Thr requirements.

Strategies to Meet Nutritional Requirements and Reduce Boar Taint in Meat from Entire Male Pigs and Immunocastrates

This paper reviews the current knowledge on the nutritional requirements of entire male and immunocastrated pigs to obtain an efficient growth, low boar taint level, and good carcass and meat quality. We present the reasons for offering entire males ad libitum access to the diets in order to optimize their protein deposition potential. Boar taint is one of the major issues in the production of entire males; therefore, the impact of various skatole- and indole-reducing feed ingredients is discussed regarding their efficiency and the possible mechanism affecting skatole and indole production in the hindgut. Entire males have lean carcasses, so their intramuscular fat content can be lower than that of surgical castrates or females and the adipose tissue can be highly unsaturated. The possible nutritional strategies to counteract these effects are summarized. We conclude that immunocastrates can be fed similarly to entire males until the second vaccination. However, due to the metabolic changes occurring shortly after the second vaccination, the requirements for essential amino acids are markedly lower in immunocastrates than in entire males.

Increasing the Hindgut Carbohydrate/Protein Ratio by Cecal Infusion of Corn Starch or Casein Hydrolysate Drives Gut Microbiota-Related Bile Acid Metabolism To Stimulate Colonic Barrier Function

Dietary high protein and low carbohydrate levels compromise colonic microbiota and bile acid metabolism, which underlies a detrimental gut environment. However, it remains unclear if the diet-induced changes in colonic health are due to a change in hindgut nutrient availability and what key intermediates link the microbe-epithelium dialogue. To specifically alter the hindgut nutrient substrate availability, here we used a cecally cannulated pig model to infuse corn starch and casein hydrolysate directly into the cecum to generate a stepwise change of carbohydrate/nitrogenous compound (C/N) ratio. Pigs were cecally infused daily with either saline (Control), corn starch (Starch), or casein hydrolysate (Casein) (n = 8 per group), respectively, for 19 days. After infusion, C/N ratios in colonic digesta were 16.33, 12.56, and 8.54 for the starch, control, and casein groups, respectively (P < 0.05). Relative to the control group, casein infusion showed greater abundance of the bacteria (Eubacterium) capable of bile acid 7α-dehydroxylation (baiJ), higher levels of expression of bacterial genes encoding the baiJ enzyme, and higher levels of secondary bile acid (deoxycholic acid [DCA] and lithocholic acid [LCA]), while the starch infusion showed the opposite effect. Correspondingly, casein infusion downregulated expression of genes encoding tight junction proteins (ZO-1 and OCLD) and upregulated expression of genes encoding epidermal growth factor receptor (EGFR). The ratio of C/N was linearly related with the concentrations of DCA and LCA and gene expression levels of ZO-1, occludin, and EGFR. Caco-2 cell experiments further showed that DCA and LCA downregulated expression of genes involved in barrier function (ZO-1 and OCLD) and upregulated the gene expression of EGFR and Src. Inhibition of EGFR and Src could abolish DCA- and LCA-induced downregulation of ZO-1, indicating that DCA and LCA impair gut barrier function via enhancing the EGFR-Src pathway. These results suggest that the ratio of C/N in the large intestine is an important determinant of microbial metabolism and gut barrier function in the colon. The findings provide evidence that microbe-related secondary bile acid metabolism may mediate the interplay between microbes and gut barrier function.

IMPORTANCE High-fiber or high-protein diets could alter gut microbiota and health in the large intestine, but factors involved in the effects remain unclear. The present study for the first time demonstrates that the starch- and casein-induced C/N ratio in the hindgut is an important factor. Using the cannulated pig model, we found that the distinct C/N ratio induced by cecal infusion of corn starch or casein hydrolysate was linearly correlated with microbial metabolites (secondary bile acids) and tight junction proteins (ZO-1 and OCLD). Cell culture study further demonstrates that the gut microbial metabolites (DCA and LCA) could impair the intestinal barrier function via the EGFR-Src pathway. These suggest that DCA and LCA were key metabolites mediating microbe-epithelium dialogue when the hindgut C/N ratios were altered by cecal infusion of corn starch or casein hydrolysate. These findings provide new insight into the impact of C/N ratio in the large intestine on colonic health and provide a new framework for therapeutic strategy in gut health through targeted manipulation of hindgut microbiota by increasing the carbohydrate level in the large intestine.

Tryptophan Metabolism: A Link Between the Gut Microbiota and Brain

The gut-brain axis (GBA) is a bilateral communication network between the gastrointestinal (GI) tract and the central nervous system. The essential amino acid tryptophan contributes to the normal growth and health of both animals and humans and, importantly, exerts modulatory functions at multiple levels of the GBA. Tryptophan is the sole precursor of serotonin, which is a key monoamine neurotransmitter participating in the modulation of central neurotransmission and enteric physiological function. In addition, tryptophan can be metabolized into kynurenine, tryptamine, and indole, thereby modulating neuroendocrine and intestinal immune responses. The gut microbial influence on tryptophan metabolism emerges as an important driving force in modulating tryptophan metabolism. Here, we focus on the potential role of tryptophan metabolism in the modulation of brain function by the gut microbiota. We start by outlining existing knowledge on tryptophan metabolism, including serotonin synthesis and degradation pathways of the host, and summarize recent advances in demonstrating the influence of the gut microbiota on tryptophan metabolism. The latest evidence revealing those mechanisms by which the gut microbiota modulates tryptophan metabolism, with subsequent effects on brain function, is reviewed. Finally, the potential modulation of intestinal tryptophan metabolism as a therapeutic option for brain and GI functional disorders is also discussed.

Cell Wall Integrity of Pulse Modulates the in Vitro Fecal Fermentation Rate and Microbiota Composition

The physical structure of type 1 resistant starch (RS 1) could influence the metabolite production and stimulate the growth of specific bacteria in the human colon. In the present study, we isolated intact cotyledon cells from pinto bean seeds as whole pulse food and RS 1 model and obtained a series of cell wall integrities through controlled enzymolysis. In vitro human fecal fermentation performance and microbiota responses were tested, and we reported that the cell wall integrity controls the in vitro fecal fermentation rate of heat-treated pinto bean cells. The concentration of butyrate produced by pinto bean cell fermentation enhanced with weakened cell wall integrity, and certain beneficial bacterial groups such as Blautia and Roseburia genera were remarkably promoted by pinto bean cells with damaged cell wall integrity. However, the intact cell sample had a shape more similar to microbiota composition with the purified cell wall polysaccharides, rather than the damaged cells.

The preparation, formation, fermentability, and applications of resistant starch

Resistant starch (RS) cannot be digested in the small intestine but can be fermented by microflora in the colon. To meet the demand for RS, effective methods and advanced equipment for preparing RS have emerged, but further development is needed. RS contents are affected by different prepared methods, starch source and certain nutrients such as protein, phenols, and hydrocolloids interacted with RS. As a beneficial fermentation substrate, RS modifies and stabilizes the intestinal flora to balance the intestinal environment and improve intestinal tract health and function. RS is also a kind of ingredient with potential physiological function, even better than that dietary fiber, but also in terms of providing various health benefits. RS has good food-processing characteristics as well and can thus be widely used in the food industry.

Changes in the intestine microbial, digestion and immunity of Litopenaeus vannamei in response to dietary resistant starch

Resistant starch (RS) is a constituent of dietary fibre that has beneficial effects on the intestine physiological function of animals. However, the roles of RS on shrimp intestine health is unknown. In this study, we investigated the the effects of dietary RS on the microbial composition, and digestive and immune-related indices in the intestine of Litopenaeus vannamei. The shrimp were fed with diets containing different levels of RS: 0 g/kg (Control), 10 g/kg (RS1), 30 g/kg (RS2) and 50 g/kg (RS3) for 56 days. The results showed that dietary RS improved the morphology of the intestine mucosa. RS also increased the activity of digestive enzymes (AMS, LPS, Tryp, and Pep) and immune enzymes (PO, T-AOC, T-NOS, and NO), and the expression levels of immune-related genes (proPO, ALF, Lys, HSP70, Trx, Muc-1, Muc-2, Muc-5AC, Muc-5B, and Muc-19). A microbiome analysis indicated that dietary RS increased the short-chain fatty acids (SCFAs) contents and altered the composition of the intestine microbial. Specifically, RS increased the abundances of Proteobacteria and decreased the abundance of Bacteroidetes. At the genus level, the beneficial bacteria (Lutimonas, Ruegeria, Shimia, Mesoflavibacter, and Mameliella) were enriched, which might be involved in degrading toxins and producing beneficial metabolites; while potential pathogens (Formosa and Pseudoalteromonas) were decreased in response to dietary RS. Our results revealed that dietary RS could improve the intestine health of L. vannamei, probably via modulating the intestine microbial composition and SCFAs contents, and enhancing the digestion and immunity of the shrimp.