Magnesium requirement of some of the principal rumen cellulolytic bacteria

Oral magnesium prevents acetaminophen-induced acute liver injury by modulating microbial metabolism

Acetaminophen overuse is a common cause of acute liver failure (ALF). During ALF, toxins are metabolized by enzymes such as CYP2E1 and transformed into reactive species, leading to oxidative damage and liver failure. Here, we found that oral magnesium (Mg) alleviated acetaminophen-induced ALF through metabolic changes in gut microbiota that inhibit CYP2E1. The gut microbiota from Mg-supplemented humans prevented acetaminophen-induced ALF in mice. Mg exposure modulated Bifidobacterium metabolism and enriched indole-3-carboxylic acid (I3C) levels. Formate C-acetyltransferase (pflB) was identified as a key Bifidobacterium enzyme involved in I3C generation. Accordingly, a Bifidobacterium pflB knockout showed diminished I3C generation and reduced the beneficial effects of Mg. Conversely, treatment with I3C or an engineered bacteria overexpressing Bifidobacterium pflB protected against ALF. Mechanistically, I3C bound and inactivated CYP2E1, thus suppressing formation of harmful reactive intermediates and diminishing hepatocyte oxidative damage. These findings highlight how interactions between Mg and gut microbiota may help combat ALF.

Effects of calcium-magnesium carbonate and calcium-magnesium hydroxide as supplemental sources of magnesium on ruminal microbiome

Our objective was to evaluate the inclusion of calcium-magnesium carbonate [CaMg(CO₃)₂] and calcium-magnesium hydroxide [CaMg(OH)₄] in corn silage-based diets and their impact on ruminal microbiome. Our previous work showed a lower pH and molar proportion of butyrate from diets supplemented with [CaMg(CO₃)₂] compared to [CaMg(OH)₄]; therefore, we hypothesized that ruminal microbiome would be affected by Mg source. Four continuous culture fermenters were arranged in a 4 × 4 Latin square with the following treatments defined by the supplemental source of Mg: 1) Control (100% MgO, plus sodium sesquicarbonate as a buffer); 2) CO₃ [100% CaMg(CO₃)₂]; 3) OH [100% CaMg(OH)₄]; and 4) CO₃/OH [50% Mg from CaMg(CO₃)₂, 50% Mg from CaMg(OH)₄]. Diet nutrient concentration was held constant across treatments (16% CP, 30% NDF, 1.66 MCal NEl/kg, 0.67% Ca, and 0.25% Mg). We conducted four fermentation periods of 10 d, with the last 3 d for collection of samples of solid and liquid digesta effluents for DNA extraction. Overall, 16 solid and 16 liquid samples were analyzed by amplification of the V4 variable region of bacterial 16S rRNA. Data were analyzed with R and SAS to determine treatment effects on taxa relative abundance of liquid and solid fractions. Correlation of butyrate molar proportion with taxa relative abundance was also analyzed. Treatments did not affect alpha and beta diversities or relative abundance of phylum, class and order in either liquid or solid fractions. At the family level, relative abundance of Lachnospiraceae in solid fraction was lower for CO₃ and CO₃/OH compared to OH and Control (P < 0.01). For genera, abundance of Butyrivibrio (P = 0.01) and Lachnospiraceae ND3007 (P < 0.01) (both from Lachnospiraceae family) was lower and unclassified Ruminococcaceae (P = 0.03) was greater in CO₃ than Control and OH in solid fraction; while abundance of Pseudobutyrivibrio (P = 0.10) and Lachnospiraceae FD2005 (P = 0.09) (both from Lachnospiraceae family) and Ruminobacter (P = 0.09) tended to decrease in CO₃ compared to Control in liquid fraction. Butyrate molar proportion was negatively correlated to Ruminococcaceae (r = –0.55) in solid fraction and positively correlated to Pseudobutyrivibrio (r = 0.61) and Lachnospiraceae FD2005 (r = 0.61) in liquid. Our results indicate that source of Mg has an impact on bacterial taxa associated with ruminal butyrate synthesis, which is important for epithelial health and fatty acid synthesis.

Influence of zeolite (clinoptilolite) supplementation on characteristics of digestion and ruminal fermentation of steers fed a steam-flaked corn-based finishing diet

Four Holstein steers (328 ± 14 kg) with ruminal and duodenal cannulas were used in a 4 × 4 Latin square design to examine the effect of level of zeolite supplementation (0, 10, 20 or 30 g clinoptilolite-Ca/kg of diet) in a steam-flaked corn-based finishing diet on the characteristics of ruminal fermentation and nutrient digestion. Zeolite was top-dressed with the basal diet at time of feeding; therefore, intake of organic matter (OM), neutral detergent fibre (NDF), starch and N was equal in all treatments. Zeolite supplementation did not affect site and extent of digestion of N or NDF. Zeolite linearly decreased (P < 0.01) NH3-N flow to duodenum, but did not affect duodenal flow of microbial N, feed N, or microbial efficiency. Inclusion of zeolite linearly increased (P = 0.02) ruminal OM digestion and tended (linear, P = 0.08) to increase ruminal digestion of starch. Zeolite supplementation increased (linear effect, P < 0.01) faecal excretion of ash, resulting in decreased total tract DM digestion (linear effect, P = 0.04). However, total tract digestion of OM tended to increase (P = 0.06) with increasing zeolite supplementation. Thus, dilution of the diet with zeolite did not depress dietary digestible energy. There were no treatment effects on ruminal pH. Total ruminal volatile fatty acid concentration tended (P = 0.08) to increase as zeolite increased. Zeolite supplementation decreased ruminal molar proportion of acetate and increased molar proportion of propionate (linear effect, P < 0.01), resulting in decreased (linear effect, P < 0.01) of acetate: propionate ratio. Supplementation with zeolite at levels of up to 30 g of zeolite/kg of diet may enhance ruminal OM digestion, largely due to the tendency of increased ruminal starch digestion. Zeolite supplementation altered ruminal volatile fatty acid molar proportions (decreased acetate : propionate ratio), and therefore may have an positive impact on energy efficiency.