Hydrogen and methane emissions from beef cattle and their rumen microbial community vary with diet, time after feeding and genotype

The aims of the present study were to quantify hydrogen (H-2) and methane (CH4) emissions from beef cattle under different dietary conditions and to assess how cattle genotype and rumen microbial community affected these emissions. A total of thirty-six Aberdeen Angus-sired (AAx) and thirty-six Limousin-sired (LIMx) steers were fed two diets with forage: concentrate ratios (DM basis) of either 8:92 (concentrate) or 52:48 (mixed). Each diet was fed to eighteen animals of each genotype. Methane (CH4) and H-2 emissions were measured individually in indirect respiration chambers. H-2 emissions (mmol/min) varied greatly throughout the day, being highest after feed consumption, and averaged about 0.10 mol H-2/mol CH4. Higher H-2 emissions (mol/kg DM intake) were recorded in steers fed the mixed diet. Higher CH4 emissions (mol/d and mol/kg DM intake) were recorded in steers fed the mixed diet (P