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

Eructation of greenhouse gases from cattle represents an environmental concern and can significantly impact cattle’s energetic metabolism. This study was designed to assess the effectiveness of medium-chain fatty acids (MCFA) on ruminal greenhouse gas production (CH4 and CO2) and diet digestibility (IVDMD). The MCFA were produced by a novel bioprocess of microbial chain elongation using agriculture and food production sidestreams, resulting in the production of caproic acid (C6) and caprylic acid (C8). Seven different treatments were tested in in vitro fermentations that lasted 24 or 48 hours: 1) Basal diet with no inclusion of MCFA (CTRL); 2) C6 with maltodextrin (C6_P1); 3) C6 with maltodextrin and gum arabic (C6_P2); 4) C8 with maltodextrin (C8_P3); 5) C8 with maltodextrin and gum arabic (C8_P4); 6) C6 salt (C6_Salt); and 7) C8 salt (C8_Salt). The MCFA were added to the CTRL diet at 1% of dry matter to create the aforementioned treatments 2 to 7. As expected, IVDMD was greater for 48 than 24 hours (57.3 vs. 42.6%; P<0.001). No treatment-by-time interaction was observed for IVDMD (P=0.56), but an overall effect of treatment was observed (P=0.03) with C6_P2 having the highest overall IVDMD (51.21%), which differed from CTRL (48.98%). There was no difference in the total volume of gas produced by any treatment (P=0.58). However, the percentage of CH4 was lowest (P<0.001) in C6_P1, followed by C8_P3, and both differed from CTRL. The percentage of CO2 was lowest (P<0.001) in C8_Salt, and all the MCFA treatments had lower CO2% than CTRL. Furthermore, CH4 yield was lowest (P=0.001) in C6_P1, which differed from CTRL (73.39 vs. 78.52 mL/gDMD). The CO2 yield was lowest (P<0.001) in C8_Salt, and all the MCFA treatments had lower CO2 yield than CTRL. Although additional studies are currently being performed with the MCFA, these initial results reveal that these novel products can significantly reduce in vitro production of greenhouse gases from ruminal fermentation.