Dietary manipulation: a sustainable way to mitigate methane emissions from ruminants

Table 1 Volatile fatty acids production (VFA) and reductive process in the rumen adopted from [95, 96]

Substrate		Products	∆G (KJ)¹	Reactions
VFA production
C₆H₁₂O₆ + 2H₂O	→	2 C₂H₄O₂ + 2 CO₂ + 8H⁺		Acetate production
C₆H₁₂O₆ + 4H⁺	→	2 C₃H₆O₃ + 2 H₂O		Propionate production
C₆H₁₂O₆	→	C₄H₈O₄ + 2 CO₂ + 4H⁺		Butyrate production
Reductive process
CO₂ + 4H₂	→	CH₄ + 2 H₂O	− 67.4	Methane production
2 CO₂ + 4H₂	→	C₂H₄O₂ + 2 H₂O	−8.8	Reductive acetogenesis
SO₄²⁻ + 4H₂ + H⁺	→	HS⁻ + 4 H₂O	− 84.4	Sulfate reduction
NO₃⁻ + 4H₂ + 2H⁺	→	NH₄ + 3 H₂O	− 371	Nitrate reduction

¹under following rumen conditions: H₂ = 162 pa; pH = 6.5; [H₂O] = 50 M; [succinate²⁻] = 4 × 10^− 6 M; [malate²⁻] = [β-hydroxybutyryl-CoA] = [butyryl-CoA] = 10^− 6 M; [acetate⁻] = 70 mM; [propionate⁻] = 25 mM; [butyrate⁻] = 15 mM; [lactate⁻] = 1 mM; [NH₄⁺] = 11 mM (20 mg/dL); [HS⁻] = 0.14 mM. ∆G = free energy change indicates how energetically favourable it is i.e. the higher ∆G, the more energy utilization and negative ∆G indicates the energy release

ISSN: 2055-0391