290 Novel medium-chain fatty acid products derived from agriculture and food production systems decrease cattle greenhouse gas emissions in vitro.

Abstract Methane (CH4) and carbon dioxide (CO2) are the main gas products of microbial fermentation that occurs in the rumen. Although production of CH4 and CO2 is inevitable, it can be reduced. Moreover, gas production is strongly correlated to dry matter digestibility (DMD) in the rumen. The objective of this study was to conduct in-vitro fermentations using a 50:50 mixture of concentrate and forage substrates supplemented with novel medium-chain fatty acids (MCFA). The MCFA were created by a novel bioprocess of microbial chain elongation from waste of agriculture and food industries, resulting in the production of caproic acid (C6) and caprylic acid (C8). Seven different treatments were evaluated using in-vitro fermentations that lasted either 24 or 48 hours: 1) Control 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 CTRL at 1% inclusion (DM basis) to create MCFA Treatments 2 to 7. The total mixed ration was prepared using hay, dried distillers’ grains, corn, and a mineral mix. DMD was calculated as the disappearance of DM during fermentation. Total gas was collected at seven different timepoints and analyzed using gas chromatography. Data were analyzed using a general linear model that included the effects of time, treatments, and their interactions. Treatments had a significant impact on DMD% (p=0.033). C6_P2 had the largest DMD% out of all treatments, which was found to be different than CTRL. Time significantly impacted DMD% (42.6% for 24h vs. 57.3% for 48h, p< 0.001). Treatments had a significant effect on CH4% (p< 0.001), with C6_P1 producing the smallest CH4% out of all treatments. There was an effect of treatment on CO2% (p< 0.001). C8_Salt, followed by C6_Salt, produced the smallest CO2%, but all MCFA had CO2% lower than that of CTRL. CH4 yield (mL/g DMD) was significantly affected by treatment (p=0.001), and CH4 yield was lowest for C6_P1. CO2 yield (mL/g DMD) was significantly affected by treatment (p< 0.001). C8_Salt, followed by C6_Salt, yielded the least CO2, but all MCFA had CO2 yield lower than that of CTRL. This preliminary study highlighted significant effects of novel MCFA on gas production and composition using an in-vitro fermentation ruminal model. Additional studies are being executed to determine anti-methanogenic effects of MCFA working in tandem and at different dietary inclusions, as well as volatile fatty acid and microbiome analysis.