Effects of elemental magnesium and magnesium oxide on hydrogen, methane and volatile fatty acids production in in vitro rumen batch cultures

Abstract This study aimed to examine the hypothesis that extra molecular hydrogen (H 2 ) produced by elemental magnesium (Mg) could alter rumen fermentation and methanogenesis in in vitro batch incubation. As elevated Mg 2+ may exert negative effects on rumen fermentation, magnesium oxide (MgO) was also included for comparison. Mulberry leaf and corn grain had contrast chemical composition and thus were selected as substrates for incubation. Both elemental Mg and MgO were supplemented at two levels, i.e. 0.625 and 1.25 mmol/bottle. The in vitro incubation was performed for 48 h to measure gas production (GP), H 2 gas (gH 2 ) and methane gas (gCH 4 ) production, dissolved H 2 and CH 4 concentrations, and volatile fatty acids (VFA) production. Elemental Mg or MgO supplementation increased ( P linear 2+ concentration and pH in comparison to the control without supplements. There was no statistical difference ( P > 0.05) in ruminal Mg 2+ concentration between MgO and elemental Mg supplementation. Elemental Mg increased ( P 2 and gCH 4 production, dissolved H 2 and CH 4 concentrations, in comparison to the control and MgO supplementation. Elemental Mg and MgO supplementation had lower ( P linear P P 2+ concentration (> 5.5 mM) inhibits ruminal fermentation. Extra H 2 produced by elemental Mg supplementation has a biological function to inhibit rumen fermentation, enhances ruminal methanogenesis and shifts the fermentation pathway from acetate to propionate production.