Medium-Chain Fatty Acid Products Derived from Agriculture and Food Production Sidestreams Decrease Cattle Greenhouse Gas Emissions In Vitro

Impacts of including medium-chain fatty acid (MCFA) products in cattle diets on dry matter digestibility (DMD), volatile fatty acid (VFA), and ruminal gas production were assessed in vitro. Two MCFAs—caproic acid (C6) and caprylic acid (C8)—were produced by a novel bioprocess using agriculture and food waste and microencapsulated with maltodextrin for fast release (FR) and gum arabic for slow release (SR) in addition to C6 and C8 salts. The MCFAs were tested alone and in combination at 1% of dietary dry matter, resulting in eighteen treatments, including a control without MCFA. No treatment reduced DMD%, CH4%, or CH4 yield compared to the control. All treatments except T3 (C8 FR) decreased (p ≤ 0.05) CO2% compared to the control. Certain combinations of MCFA products reduced (p < 0.001) total gas yield and CO2 yield compared to the control, with T17 (C6 FR, C6 SR, C8 FR, C8 SR) having the strongest effect: a total gas yield reduction of 13.9% and a CO2 yield reduction of 29.8%. There was a treatment effect (p ≤ 0.05) on all VFA molar proportions, excluding valerate (p = 0.24). Overall, the MCFA products affected several ruminal fermentation parameters and substantially reduced CO2 production.