Swine diets: Impact of carbohydrate sources on manure characteristics and gas emissions

A dietary pattern promoting gut sulfur metabolism is associated with increased mortality and altered circulating metabolites in low-income American adults

BACKGROUND

Excessive hydrogen sulfide in the gut, generated by sulfur-metabolising bacteria from foods, has been linked to intestinal inflammation and human diseases. We aim to investigate the interplay between diet and sulphur-metabolising bacteria in relation to mortality and circulating metabolites in understudied populations.

METHODS

In the Southern Community Cohort Study (SCCS), a prospective cohort of primarily low-income American adults, habitual diets were assessed using a food frequency questionnaire at baseline (2002-2009). A sulfur microbial diet score (SMDS) was developed among 514 Black/African American participants by linking habitual dietary intakes with the abundance of sulfur-metabolising bacteria profiled by faecal shotgun metagenomics. The SMDS was then constructed among all eligible SCCS participants (50,114 Black/African American and 23,923 non-Hispanic White adults), and its associations with mortality outcomes were examined by Cox proportional hazards model and Fine-Grey subdistribution hazard model. The association between SMDS and 1110 circulating metabolites was examined by linear regression among 1688 SCCS participants with untargeted metabolomic profiling of baseline plasma samples.

FINDINGS

Over an average 13.9-year follow-up, SMDS was associated with increased all-cause mortality (HR [95% CI] for the highest vs. lowest quartiles: 1.21 [1.15-1.27]) and cardiovascular disease (1.18 [1.08-1.29]), cancer (1.13 [1.02-1.25]), and gastrointestinal cancer-specific (1.22 [1.00-1.49]) mortality among Black/African American participants (all P-trend<0.05). The associations were largely consistent across participant subgroups. Similar results were observed among non-Hispanic White participants. The SMDS was associated with 112 circulating metabolites, which mediated 36.15% of the SMDS-mortality association (P = 0.002).

INTERPRETATION

A dietary pattern promoting sulfur-metabolising gut bacteria may contribute to increased total and disease mortality in low-income American adults.

FUNDING

This study was funded by the National Institutes of Health, United States, to Vanderbilt University Medical Center, United States, and Anne Potter Wilson Chair endowment to Vanderbilt University, United States.

Anti-Inflammatory Effects of Hydrogen Sulfide in Axes Between Gut and Other Organs

Significance: Hydrogen sulfide (H2S), a ubiquitous small gaseous signaling molecule, plays a critical role in various diseases, such as inflammatory bowel disease (IBD), rheumatoid arthritis (RA), ischemic stroke, and myocardial infarction (MI) via reducing inflammation, inhibiting oxidative stress, and cell apoptosis. Recent Advances: Uncontrolled inflammation is closely related to pathological process of ischemic stroke, RA, MI, and IBD. Solid evidence has revealed the axes between gut and other organs like joint, brain, and heart, and indicated that H2S-mediated anti-inflammatory effect against IBD, RA, MI, and ischemic stroke might be related to regulating the functions of axes between gut and other organs. Critical Issues: We reviewed endogenous H2S biogenesis and the H2S-releasing donors, and revealed the anti-inflammatory effects of H2S in IBD, ischemic stroke, RA, and MI. Importantly, this review outlined the potential role of H2S in the gut-joint axis, gut-brain axis, and gut-heart axis as a gasotransmitter. Future Direction: The rate, location, and timing of H2S release from its donors determine its potential success or failure as a useful therapeutic agent and should be focused on in the future research. Therefore, there is still a need to explore internal and external sources monitoring and controlling H2S concentration. Moreover, more efficient H2S-releasing compounds are needed; a better understanding of their chemistry and properties should be further developed. Antioxid. Redox Signal. 42, 341-360.

Evaluation of pollution potential in swine manure across growth stages: Impact of dietary nutrients and management strategies

Regulation of dietary nutrient fractions to control the release of labile manure pollutants in swine production remains a challenge. Feeding trials were conducted to assess the impact of dietary nutrient fractions on labile manure composition and pollution potential in pigs at different growth stages. The pigs were selected based on age (weaning = 60 days, feeding = 100 days, and finishing = 160 days), health, and average body weight (23.7 kg, 50.5 kg, and 109.0 kg respectively) and fed with (1) high, (2) medium, and (3) low energy diets twice daily in all three growth stages. Urine and feces were collected for analysis. The study utilized correlation, nutrient balance analysis, and theoretical models to evaluate the dietary impact on nutrient distribution and pollution potential. Results showed higher nutrient retention (N, P, Cu, Zn) with the high-energy diet across all growth stages compared to the other two diet energy levels. Correlation analysis revealed that pigs' weight gain does not reflect dietary efficiency nor indicate lower pollution potential from nutrient retention. However, dietary nutrient fractions played more significant role in labile manure release compare to the total manure component. Overall, the dietary regulatory approach offers a sustainable strategy to mitigate environmental pollution while supporting nutrient recycling using manure with lower pollutant loads.

Swine manure management by hydrothermal carbonization: Comparative study of batch and continuous operation

Hydrothermal carbonization (HTC) is considered a promising technology for biomass waste management without pre-drying. This study explores the potential for swine manure management by comparing batch and continuous processes, emphasizing the benefits of the continuous mode, particularly for its potential full-scale application. The continuous process at low temperature (180 °C) resulted in a hydrochar with a lower degree of carbonization compared to the batch process, but similar characteristics were found in both hydrochars at higher operating temperatures (230-250 °C), such as C content (∼ 52 wt%), fixed carbon (∼ 24 wt%) and higher calorific value (21 MJ kg-1). Thermogravimetric and combustion analyses showed that hydrochars exhibited characteristics suitable as solid biofuels for industrial use. The process water showed a high content of organic matter as soluble chemical oxygen demand (7-22 g L-1) and total organic carbon (4-10 g L-1), although a high amount of refractory species such as N- and O-containing long aromatic compounds were detected in the process water from the batch process, while the process water from the continuous process presented more easily biodegradable compounds such as acids and alcohols, among others. The longer time required to reach operating temperature in the case of the batch system (longer heating time to reach operating temperature) resulted in lower H/C and O/C ratios compared to hydrochar from the continuous process. This indicates that the dehydration and decarboxylation reactions of the feedstock play a more important role in the batch process. This study shows the efficiency of the continuous process to obtain carbonaceous materials suitable for use as biofuel, providing a solution for swine manure management.

Impact of diet on hydrogen sulfide production: implications for gut health

PURPOSE OF REVIEW

Excessive hydrogen sulfide (H 2 S) production by the gut microbiota may contribute to the pathogenesis of multiple intestinal diseases, including colon cancer and ulcerative colitis. Therefore, understanding of dietary drivers of H 2 S production has potential implications for nutritional strategies to optimize gut health and treat intestinal diseases.

RECENT FINDINGS

Recent studies support a positive relationship between dietary protein intake and H 2 S production. However, protein rarely exists in isolation in the diet, and dietary fiber intake could reduce H 2 S production in humans and animals, even with ∼30% of calories derived from protein.

SUMMARY

These findings suggest that increased fiber intake may reduce H 2 S production irrespective of protein intake, enabling the ability to meet the metabolic demands of the illness while supporting gut health. Here we discuss two recent ulcerative colitis diet studies that illustrate this point.

Environmental impacts of eco-nutrition swine feeding programs in spatially explicit geographic regions of the United States

This study was conducted to determine greenhouse gas (GHG) emissions, water consumption, land use, as well as nitrogen (N), phosphorus (P), and carbon (C) balance of five diet formulation strategies and feeding programs for growing-finishing pigs (25-130 kg body weight) in the three spatially explicit geographic regions where the majority of U.S. pork production occurs. Feeding programs evaluated consisted of 1) standard corn-soybean meal (CSBM) diets, 2) CSBM containing 15% corn distillers dried grains with solubles (DDGS), 3) CSBM with 8.6% thermally processed supermarket food waste (FW), 4) low crude protein CSBM diets supplemented with synthetic amino acids (SAA), and 5) CSBM with phytase enzyme (PHY) added at 600 FTU (phytase units)/kg of diet. An attributional Life Cycle Assessment approach using a highly specialized, spatially explicit Food System Supply-Chain Sustainability (FoodS3) model was used to quantify GHG emissions, water consumption, and land use of corn, soybean meal, and DDGS based on county level sourcing. The DDGS, FW, and SAA feeding programs had less estimated N and P intake and excretion than CSBM, and the PHY feeding program provided the greatest reduction in P excretion. The FW feeding program had the least overall GHG emissions (319.9 vs. 324.6 to 354.1 kg CO2 equiv./market hog), land use (331.5 vs. 346.5 to 385.2 m2/market hog), and water consumption (7.64 vs. 7.70 to 8.30 m3/market hog) among the alternatives. The DDGS feeding program had the greatest GHG emissions (354.1 kg CO2 equiv./market hog) among all programs but had less impacts on water consumption (7.70 m3) and land use (346.5 m2) per market hog than CSBM and PHY. The SAA feeding program provided a 6.5-7.4% reduction in land use impacts compared with CSBM and PHY, respectively. Regardless of feeding program, the Midwest had the least contributions to GHG emissions and land use attributed to feed and manure among regions. Water consumption per market hog associated with feeding programs was much greater in the Southwest (59.66-63.58 m3) than in the Midwest (4.45-4.88 m3) and Mid-Atlantic (1.85-2.14 m3) regions. Results show that diet composition and U.S. geographic region significantly affect GHG emissions, water consumption, and land use of pork production systems, and the potential use of thermally processed supermarket food waste at relatively low diet inclusion rates (<10%) can reduce environmental impacts compared with other common feeding strategies.