Search Results (78)

The attraction of neonatal piglets to sow feces and their coprophagy suggests that fecal semiochemicals promote nutrient intake and gut colonization, but their microbial origin is poorly understood. This study explored associations between gut microbiota and fecal semiochemical/metabolic profiles in prepartum and postpartum sows. Fecal samples were collected from six crossbred sows at 4 days prepartum and 3 days postpartum. Nutritional components, volatile organic compounds (VOCs), untargeted metabolomics, and gut microbiota were analyzed. Nutritional composition remained largely stable postpartum, except that sodium increased while potassium, magnesium, and cellulose decreased. Skatole and p-cresol concentrations increased postpartum even after dry matter correction. Untargeted metabolomics identified 298 differentially abundant metabolites (250 up, 48 down) postpartum, enriched in nicotinamide/nicotinate metabolism, arginine biosynthesis, and others. Gut microbial alpha diversity (Shannon, Chao1, observed features) decreased postpartum. Fibrolytic and butyrate-producing bacteria (e.g., Ruminococcaceae UCG-005, Lachnospira) were enriched prepartum, whereas Escherichia-Shigella, Christensenellaceae R-7 group and Enterococcus were more abundant postpartum. Spearman correlations showed skatole and p-cresol were strongly negatively correlated with butyrate-producing bacteria and positively correlated with postpartum-enriched genera. This study uncovered prepartum-to-postpartum shifts in sow fecal components and microbiota, revealing a microbial basis for semiochemical production and offering probiotic insights using coprophagy to improve piglet health. Full article

Accurate and physiologically relevant in vitro models are needed to predict nutrient digestibility and hindgut fermentation in pigs, as conventional in vivo trials are resource-intensive and raise animal welfare concerns. This study evaluated and compared the predictive performance of three in vitro digestion approaches—shaking (S), dialysis (D), and a combined shaking plus dialysis (SD) method—for estimating in vivo apparent total tract digestibility (ATTD) and fermentation characteristics across weaning, growing, and finishing pigs. Commercial diets were subjected to simulated gastric and small-intestinal digestion using S, D, or SD, followed by fecal inoculation to model hindgut fermentation for 12 and 48 h. During the gastrointestinal phase, crude protein digestibility was highest with D (>75%), intermediate with SD, and lowest with S (50–60%), indicating that product removal by dialysis mitigated enzyme inhibition from metabolite accumulation. After 48 h of fermentation, all methods showed strong linear correlations with in vivo ATTD (r > 0.93), but only D achieved high absolute agreement (Lin’s CCC > 0.95 for dry matter and crude protein). Moreover, D and SD at 48 h closely reflected in vivo fecal profiles of skatole, indole, and microbial enzyme activities, with D at 12 h showing an especially strong correlation for protease (r = 0.98). While D provided the most precise predictions of absolute values, the SD method offered an optimal balance between physiological relevance and operational efficiency, supporting its use as a robust, high-throughput platform for porcine feed evaluation and fecal nitrogenous odorant prediction. Full article

The escalating consumption of red meat is a potent environmental risk factor for inflammatory bowel disease (IBD), which is characterized by compromised expression of the xenobiotic transporter P-glycoprotein (MDR1/ABCB1). While gut microbiota metabolize dietary tryptophan into diverse indole derivatives that function as aryl hydrocarbon receptor (AhR) ligands, their differential regulation of MDR1 remains an unresolved AhR paradox. Here, we investigated the mechanisms by which two distinct metabolites, indole-3-acetic acid (IAA) and skatole, regulate MDR1 expression in human colonic epithelial Caco-2 cells. We observed that IAA selectively enhances MDR1 protein stability via an AhR-dependent pathway without inducing de novo transcription, suggesting a mechanism we term enhanced proteostasis mediated by the AhR-Hsp90 complex. Conversely, skatole, a toxic dysbiotic metabolite linked to red meat intake, triggered a time-dependent depletion of MDR1 and potently abrogated the protective efficacy of IAA. Our findings are consistent with a model in which skatole acts as a putative structural disruptor, potentially destabilizing the chaperone complex essential for MDR1 integrity. This destruction is facilitated by a key bacterial enzyme, indoleacetate decarboxylase (IAD), which is a pH-dependent metabolic switch in the gut. The modern Western diet, characterized by high protein and low fiber content, elevates colonic pH, thereby activating IAD to convert protective IAA into toxic skatole. These findings provide a molecular framework for the red meat–microbiome–barrier failure axis and highlight the restoration of the IAA/skatole balance through dietary intervention as a promising therapeutic strategy. Full article

The rising incidence of colorectal cancer (CRC) in modernized societies is linked to diet-induced dysbiosis, characterized by a critical metabolic divergence: the depletion of protective indole-3-acetic acid (IAA) concurrent with the accumulation of toxic skatole (3-methylindole). However, the molecular mechanisms by which high concentrations of skatole drive malignancy—and whether IAA can counteract this toxicity—remain elusive. Here, we demonstrate that physiologically relevant concentrations of skatole (500 µM) significantly promote the proliferation of HCT-116 CRC cells through a “dual-hit” mechanism involving both aryl hydrocarbon receptor (AhR)-dependent genomic activity and AhR-independent activation of the ERK MAPK pathway. Notably, co-treatment with IAA (250 µM) effectively abrogated skatole-induced proliferation, restoring cell growth to baseline levels while sparing upstream MAPK phosphorylation. Mechanistic analysis indicates that IAA acts not merely as a competitor, but as a functional antagonist. Specifically, our findings suggest that IAA functions as a putative selective AhR modulator (SAhRM) that qualitatively reprograms AhR signaling. This modulation uncouples upstream MAPK phosphorylation from downstream cell cycle progression, effectively impeding the proliferative program even in the presence of skatole-induced stress. Furthermore, we propose a theoretical model of counter-balancing metabolic activation, hypothesizing that the oxidative environment associated with skatole metabolism may trigger the bioactivation of IAA into highly active anti-tumor derivatives. These findings suggest that restoring the gut IAA/skatole balance—either by targeting the bacterial enzyme indoleacetate decarboxylase (IAD) or via dietary resistant starch—may offer a promising precision nutrition strategy for CRC prevention. Full article

This study aimed to investigate the effects of pineapple pomace as a functional feed additive on growth performance, fecal microbiota composition, short-chain fatty acids (SCFAs), and odor substance emissions in weaned piglets. The experiment utilized 90 weaned three-way crossbred piglets (Duroc–Yorkshire–Guoshou Black Pig) at 28 days of age, randomly divided into three groups of 10 pigs each: the control group (CON, basal diet), the fish meal group (FM, basal diet + 2% imported fish meal), and the pineapple pomace group (PPC, basal diet + 2% pineapple pomace compound). The results indicated the PPC group exhibited significantly higher average daily gain (ADG) (p < 0.05) and significantly lower feed conversion ratio (FCR) (p < 0.05) than the CON group. 16S rRNA sequencing analysis revealed that the PPC group significantly increased fecal microbiota species richness and diversity (p < 0.01) while enriching beneficial bacteria including Lactobacillus, Bifidobacterium, and butyrate-producing bacteria such as Blautia. Concurrently, acetic acid and butyric acid levels in feces were significantly elevated in the PPC group (p < 0.05), with butyric acid production markedly higher than in the FM group (p < 0.05). However, no significant differences were observed in the levels of branched-chain fatty acids (BCFAs), such as isobutyric acid and isovaleric acid (p < 0.05). Moreover, PPC supplementation led to a significant decrease in fecal levels of indole and 3-methylindole (skatole) (p < 0.05). In summary, dietary inclusion of 2% pineapple pomace improves growth performance and intestinal health in weaned piglets by modulating the fecal microbiota, promoting beneficial SCFA production, and inhibiting protein putrefaction. These findings support PPC as an effective and sustainable alternative to fish meal, contributing to the development of environmentally friendly feeding strategies in pig production. Full article

This study involved 30 male pigs (DanBred × Duroc), which were divided into three groups of 10 animals each. Control group (C)—immunologically castrated boars with a slaughter weight of 120 kg; and experimental groups: E1—uncastrated boars with a slaughter weight of 120 kg, and E2—uncastrated boars with a slaughter weight of 105 kg. Animals from all groups were fed a complete feed mixture in a liquid form three times a day. After slaughter, their meat and backfat were analysed for the physicochemical parameters and for the contents of indole, skatole, androstenol, and androsterone. A higher protein content was determined in the meat of boars from group E1 (23.48%) compared to those from groups C (22.87%) and E2 (22.99%) (p ≤ 0.01), and a higher content of n-6 PUFAs in the meat of boars from group C (5.21 mg/g of meat) compared to those from group E2 (4.81 mg/g of meat) (p ≤ 0.05). Analysis of the chemical composition of backfat showed a lower protein level in the backfat of boars from group C (4.70%) compared to those from group E1 (6.20%) and a higher fat level in the backfat from boars from group C (70.09%) compared to those from groups E1 (65.90%) and E2 (64.75%) (p ≤ 0.05). Body weight and immunocastration status were also shown to affect the fatty acid profile. Immunocastration also reduced the content of androstenol and androsterone in meat and fat. A higher content of indole was demonstrated in the meat of boars from group C and in the backfat of those from group E2 compared to the animals from the other groups (p ≤ 0.001). Full article

Background/Objectives: Salivary volatile organic compounds (VOCs) are promising noninvasive biomarkers for a wide range of diseases. While glandular saliva, secreted by salivary glands, is a relatively pure biofluid, whole saliva is a complex mixture containing oral microbiota, food debris, and desquamated epithelial cells. Therefore, a comprehensive comparison of the VOC profiles of these two types of saliva is essential to identify biologically relevant compounds. In this study, we aimed to establish a reliable method for VOC profiling from small saliva volumes and identify VOCs that reflect the biological differences between glandular and whole saliva. Methods: We developed a protocol combining MonoTrap extraction with dichloromethane, allowing the analysis of VOCs from just 100 µL of saliva. To address the issue of sampling-derived artifacts, we implemented a two-step blank analysis to systematically exclude compounds originating from the collection device. Results: Our analysis successfully identified a total of 72 VOCs. Following blank analysis, we systematically excluded 15 artifacts originating from the sampling device. Subsequent orthogonal partial least squares discriminant analysis (OPLS-DA) and Wilcoxon signed-rank test (using variable importance for prediction (VIP) > 1.0 and q < 0.05) identified 10 key VOCs that were significantly higher in whole saliva than in glandular saliva. These compounds included isobutyric acid, isovaleric acid, 4-methylvaleric acid, 3-phenylpropionic acid, indole, skatole, methyl mercaptan, 1-propanol, δ-valerolactam, and acetaldehyde. Most of these compounds originate from the metabolic activities of the oral microbiome, suggesting that the distinct VOC profile of whole saliva is predominantly influenced by microbial activity. Conclusions: Our findings demonstrated the effectiveness of this method for identifying biologically relevant VOCs from relatively small sample volumes. The identified VOC profiles highlight the contribution to the discovery of non-invasive biomarkers for oral health and serve as a solid foundation for future research into clinical applications. Full article

Activated charcoal (AC) is an adsorbent that can prevent the accumulation of boar taint-causing compounds in the fat, but is not an approved dietary additive for livestock animals. Biochar (BC) is a similar feed-approved charcoal adsorbent that may be an alternative dietary additive to control boar taint. This study was conducted to evaluate AC and BC, both in vitro and in vivo, as dietary treatments for boar taint. This was done by first conducting an in vitro binding study to compare binding between AC, BC, and spent filter aid (SFA) for boar taint compounds. Results of the in vitro study showed that both AC and BC had significantly higher B_max for androstenone (AC: 97.2 ± 0.4% and BC: 84.5 ± 0.8%) and skatole (AC: 106.1 ± 0.2%, BC: 113.2 ± 0.7%), compared to SFA with a B_max of 50.5 ± 0.2% for androstenone and 97.1 ± 5.3% for skatole. AC and BC were then tested as feed additives in finisher diets fed to slaughter weight boars. Both adsorbents were successful at preventing boar taint in a subset of animals (83%), while having no effect on plasma levels of estrone sulfate or androstenone, and growth and performance parameters. These findings suggest that BC is a suitable alternative for AC as a dietary additive to prevent boar taint. Full article

Hydrolyzed protein is increasingly used in pet food, especially for animals with adverse reactions to food or gastrointestinal issues. This randomized, double-blind controlled trial evaluated the effects of a diet containing hydrolyzed anchovy protein on the gut health of healthy adult West Highland white terriers (5 males, 25 females; 5.6–9 kg). The dogs were randomly assigned to a control group (CTR, n = 15), receiving a standard commercial diet, or a treatment group (TRT, n = 15), fed a diet partially replacing anchovy meal with hydrolyzed anchovy protein for 42 days. All the dogs underwent a veterinary health check at baseline (T0) and remained healthy throughout the study. The food and water intake were recorded daily. The body weight (BW), body condition score (BCS, 1–9), and fecal score (FS, 1–7) were assessed at days 0, 21, and 42. Fecal samples were collected at T0 and T42 to measure calprotectin, cortisol, and putrefactive compounds (indole and skatole). No significant differences were found between the groups in the BW, BCS, FS, calprotectin, or cortisol. However, the TRT group showed a significant reduction in fecal indole and skatole. The results suggest that hydrolyzed anchovy protein may improve gut fermentation and support better digestive health in dogs, leading to reduced fecal odor and increased owner satisfaction. Full article

The utility of four mineral adsorbents as potential feed additives to bind the boar taint compounds, androstenone and skatole, was assessed with an in vitro system. The adsorbents were bentonite (BNT), diatomaceous earth (DE), spent filter aid (SFA) and hydrated sodium–calcium aluminosilicate (HSCAS), with activated charcoal (AC) as a positive control. The binding capacity (B_max) and binding affinity (K) of androstenone (AND), estrone (E1), estrone sulfate (E1S), and skatole were estimated using the modified Michaelis–Menten kinetics. The Langmuir and Freundlich isotherm models were also used to assess the adsorption behaviour. The B_max values with AND were 77.7 ± 1.12%, 71.9 ± 1.93%, 55.0 ± 7.85%, and 69.5 ± 1.39% for BNT, DE, SFA, and HSCAS, respectively, with no differences in the binding affinity K (p > 0.05). All the mineral adsorbents had very low binding with E1S. SFA bound skatole with a B_max of 89.9 ± 1.09%, while the B_max values for skatole binding by BNT, DE and HCAS were approximately 15%. Most adsorbent–adsorbate complexes fit best with the Freundlich isotherm model. We conclude that all four mineral adsorbents bound androstenone, but not E1S, and only SFA effectively bound skatole. This suggests that SFA may act as a selective dietary binding agent to control boar taint, but further research using animal models is needed to explore the utility and selectivity of these adsorbents as feed additives to control boar taint. Full article

In a previous experiment, we showed that the odor of Bos taurus manure slurries could be improved by anaerobic incubation with the sugars glucose, lactose, and sucrose. This improvement was due to reductions in the concentrations of malodorants, including dimethyl disulfide, p-cresol, p-ethylphenol, indole, and skatole, and a shift to the production of fruity esters, including ethyl butyrate and propyl propanoate. Due to large concentrations of lactic acid produced by the sugar-amended manure slurries, we inferred that lactic acid bacteria were involved in improving the manure slurry odor. Here, through 16S rRNA amplicon sequencing for microbiome analysis, we show that lactic acid bacterial growth was promoted by the addition of all three sugars. Lactobacillus buchneri and an unknown Lactobacillus sp. were the most prominent lactic acid bacteria stimulated by sugar addition. Lactobacillales were found only in trace abundances in unamended manure slurries. The relative abundance of orders such as Clostridiales, Bifidobacteriales, and Erysipelotrichales were not noticeably affected by sugar amendment. However, the disaccharides lactose and sucrose seemed to increase the relative abundance of Bifidobacterium, whereas the monosaccharide glucose did not. We conclude that lactic acid bacteria are the primary bacteria involved in improving odor in dairy cow manure slurries and present strategies to enhance their abundance in animal wastes. Full article

Inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), in intestinal epithelial cells significantly contribute to inflammatory bowel disease (IBD) and colorectal cancer (CRC). Given our previous findings that TNF-α is upregulated in intestinal epithelial Caco-2 cells induced by skatole, a tryptophan-derived gut microbiota metabolite, the present study aimed to explore the relationship between skatole and IL-6, alongside TNF-α. Skatole elevated the promoter activity of IL-6 as well as TNF-α, and increased IL-6 mRNA expression and protein secretion. In addition to activating NF-κB, the NF-κB inhibitor BAY 11-7082 reduced skatole-induced cell survival and the mRNA expression of IL-6 and TNF-α. NF-κB activation was attenuated by the extracellular signal-regulated kinase (ERK) pathway inhibitor U0126 and the p38 inhibitor SB203580, but not by the c-Jun N-terminal kinase (JNK) inhibitor SP600125. U126 and SB203580 also decreased the skatole-induced increase in IL-6 expression. When skatole-induced AhR activation was inhibited by CH223191, in addition to promoting NF-κB activation, IL-6 expression was enhanced in a manner similar to that previously reported for TNF-α. Taken together, these results suggest that skatole-elicited NF-κB activation induces IL-6 and TNF-α expression, although AhR activation partially suppresses this process. The ability of skatole to increase the expression of IL-6 and TNF-α may significantly affect the development and progression of these diseases. Moreover, the balance between NF-κB and AhR activation appears to govern the skatole-induced increases in IL-6 and TNF-α expression. Therefore, the present findings provide new insights into the mechanisms linking tryptophan-derived gut microbiota metabolites with colorectal disease. Full article

Indole and skatole (3-methylindole, C₉H₉N) are common nitrogen-containing heterocyclic pollutants found in waste, wastewater treatment plants, and public restrooms and are the most notorious compounds in animal feces. Biodegradation was considered a feasible method for the removal of indole and skatole, but a comprehensive understanding of the metabolic pathways under both aerobic and anaerobic conditions was lacking, and the functional genes responsible for skatole biodegradation remained a mystery. Through metagenomic and gene cluster functional analysis, Acinetobacter piscicola p38 (NCBI: CP167896), genes 1650 (styrene monooxygenase: ACDW34_08180), and 1687 (styrene monooxygenase: ACDW34_08350) were identified as having the potential to degrade indole and skatole. The heterologous expression results demonstrate that the genes 1650 and 1651 (flavin reductase: ACDW34_08185), when combined, are capable of degrading indole, while the genes 1687 and 1688 (flavin reductase: ACDW34_08355), in combination, can degrade indole as well as skatole. These reactions necessitate the involvement of flavin reductase and NAD(P)H to catalyze the oxygenation process. This work aimed to provide new experimental evidence for the biodegradation of indole and skatole. This study offered new insights into our understanding of skatole degradation. The Acinetobacter_piscicola p38 strain provided an effective bacterial resource for the bioremediation of fecal indole and skatole. Full article

Testicular steroids can alter the activity and expression of enzymes within the liver and may influence the metabolism of skatole and androstenone, which are responsible for boar taint. Plasma levels of estrone sulfate (E₁S) are indicative of the steroidogenic capacity of the boar and are variable between animals of similar live weights at slaughter. This study aimed to characterize the relationship between steroidogenic capacity and the metabolism of boar taint compounds by relating plasma E₁S levels at slaughter weight to the expression levels of genes regulating the metabolism of androstenone and skatole, along with their respective metabolite profiles. RT-qPCR was used to evaluate gene expression in the liver. Hepatocytes were also isolated and treated with androstenone or skatole, with metabolite levels in the incubation media quantified by high-performance liquid chromatography. Plasma E₁S levels ranged from 2.2–108.5 ng/mL and were positively correlated with overall skatole metabolism (p = 0.038), the production of metabolites 3-methyloxindole (p = 0.026) and 3-hydroxy-3-methyloxindole (p = 0.036), and expression levels of key genes involved in skatole metabolism, specifically CYP2C33 (p = 0.0042), CYP2C49 (p = 0.022), and CYB5R1 (p = 0.017). There was no association between androstenone metabolism and plasma E₁S concentrations; however, there was evidence of possible co-regulation amongst genes involved in the metabolism of androstenone, skatole, and estrogens. These findings indicate that steroidogenic capacity is related to the rate of skatole, but not androstenone metabolism, in slaughter-weight boars. Full article

A study was conducted to determine if the odor profile of Bos taurus manure could be altered by the addition of the simple saccharides glucose, lactose, and sucrose. Sucrose was added to manure slurry at 0, 12.5, 25, 50, or 125 g L⁻¹, while glucose and lactose were added at 0, 6.45, 13.2, 26.4, or 65.8 g L⁻¹. One hundred mL slurries were incubated in capped bottles at 30 °C for four weeks. Biogas production was measured throughout the incubations, and the pH and concentrations of short-chain fatty acids were measured at the end of the incubations. Odor compounds of the final manure slurries were isolated by stir bar sorptive extraction and identified by stir bar gas chromatography/mass spectroscopy. Unamended manure had high concentrations of the typical manure malodorants phenol, p-cresol, p-ethylphenol, indole, and skatole. The addition of the sugars decreased these malodors in a dose-dependent manner. The addition of sugars shifted odor production to aliphatic esters including ethyl butyrate and propyl propanoate. The sugar-amended manure therefore had a different odor profile than the unamended manure did. The addition of sugar also caused the accumulation of short-chain fatty acids and, thus, decreased the pH of the manure. The production of lactic acid was particularly enhanced at high concentrations of sugar, suggesting that lactic acid bacteria could be responsible for changes in the odor profile. Future research will investigate if the addition of lesser concentrations of sugars or agricultural and food wastes rich in carbohydrates can reduce manure malodor. Full article