Molecular hydrogen generated by elemental magnesium supplementation alters rumen fermentation and microbiota in goats

Abstract

We tested the hypotheses that supplementation of a diet with elemental Mg increases ruminal dissolved H2 (dH2) in rumen fluid, which in turn alters rumen fermentation and microbial community in goats. In a randomised block design, twenty growing goats were allocated to two treatments fed the same basal diet with 1·45 % Mg(OH)2 or 0·6 % elemental Mg. After 28 d of adaptation, we collected total faeces to measure total tract digestibility, rumen contents to analyse fermentation end products and microbial groups, and measured methane (CH4) emission using respiration chambers. Ruminal Mg2+ concentration was similar in both treatments. Elemental Mg supplementation increased dH2 at 2·5 h post morning feeding (+180 %, P<0·001). Elemental Mg supplementation decreased total volatile fatty acid concentration (-8·6 %, P<0·001), the acetate:propionate ratio (-11·8 %, P<0·03) and fungal copy numbers (-63·6 %, P=0·006), and increased propionate molar percentage (+11·6 %, P<0·001), methanogen copy numbers (+47·9 %, P<0·001), dissolved CH4 (+35·6 %, P<0·001) and CH4 emissions (+11·7 %, P=0·03), compared with Mg(OH)2 supplementation. The bacterial community composition in both treatments was overall similar. Ruminal dH2 was negatively correlated with acetate molar percentage and fungal copy numbers (P<0·05), and positively correlated with propionate molar percentage and methanogen copy numbers (P<0·05). In summary, elemental Mg supplementation increased ruminal dH2 concentration, which inhibited rumen fermentation, enhanced methanogenesis and seemed to shift fermentation pathways from acetate to propionate, and altered microbiota by decreasing fungi and increasing methanogens.

Metabolic Hydrogen Flows in Rumen Fermentation: Principles and Possibilities of Interventions

“…[H] redirection toward alternative [H] sinks such as propionate. In agreement, the concentration of dissolved H 2 in the rumen has been reported to associate negatively with acetate and positively with propionate molar percentages (Wang et al, 2017(Wang et al, , 2018, although an association with propionate molar percentage was not observed in another study (Wang et al, 2016).…”

“…A factor potentially masking the effects of H 2 gas added to microbial cultures headspace is lack of equilibrium with dissolved H 2 (Wang et al, 2016). In that regard, two in vivo studies in which dissolved H 2 was indirectly delivered through the reaction of elemental magnesium (Mg) with water, reported decreases in total VFA concentration as a result of the augmented dissolved H 2 concentration (Wang et al, 2017;Ma et al, 2019), although the limitations of VFA concentration as a metric of rumen fermentation pointed out above are again acknowledged.…”

Effects of Licorice Extract Supplementation on Feed Intake, Digestion, Rumen Function, Blood Indices and Live Weight Gain of Karakul Sheep

“…This may be one of the reasons why a 4.5% licorice root extract supplementation reduced the ratio of acetate to propionate in the present study. The fluctuation of pH may reflect an interaction between feed intake, urea recycling from magnesium and acid production in the rumen [25] (Wang et al, 2017). It is worth noting that in the present study, the rumen liquor was sampled for one single day, and the results should be treated with caution.…”

Effects of urea plus nitrate pretreated rice straw and corn oil supplementation on fiber digestibility, nitrogen balance, rumen fermentation, microbiota and methane emissions in goats

“…After total collection, CH 4 emissions were measured for 2 d per goat by moving each goat into a respiration chamber as described by Wang et al [13]. As only three chambers were available, it took 6 d (from d 20 to 25) to complete the measurements for all goats.…”

“…Rumen contents were collected at 0, 2.5 and 6 h after morning feeding on 2 consecutive days (d 26 and d 27) using an oral stomach tube according to Wang et al [13]. About 150 mL of rumen contents were rapidly collected after discarding the initial 100 mL of rumen contents.…”