RUMENOMICS · Molecular studies of the ruminal microorganisms involved in fatty acids biohydrogenation: CLA production

Final Activity Report Summary - RUMENOMICS (Molecular studies of the ruminal microorganisms involved in fatty acids biohydrogenation: CLA production)

This project aimed to apply genomic technologies to improve our understanding of fatty acid metabolism in the rumen and to feed this information into an ongoing program on the manipulation of fatty acid metabolism in the rumen aimed at improving the quality of ruminant products. In particular we were interested in the production of conjugated linoleic acids (CLA), a group of isomers with health benefits in terms of protection against cancer, heart disease and obesity. The metabolism of fatty acids was studied in a wider context, including other aspects of the use of hydrogen in the rumen, in particular the production of methane. In preliminary in vitro experiments we observed that CLA production differed between different fractions, such as large and small particles and strained rumen fluid, in the rumen and that the surfaces of particles were the most important sites for CLA production in the rumen. We also observed that the microbial populations, namely bacteria and protozoa, were different in different rumen fractions. The area of the project where most of the scientific effort was focused was the role of protozoa in CLA production, as it was known that the CLA content of protozoa was four to five fold times higher than in bacteria. Three experiments were carried out to re-examine the role of rumen protozoa in lipid metabolism and CLA production. By using denaturing gradient gel electrophoresis (DGGE) and real time polymerase chain reaction (PCR) we established that rumen protozoa contributed to 40 % of the total flow of CLA and TVA to the duodenum. We also determined that when protozoa were not present in the rumen there was more CLA produced, although the shift in the bio-hydrogenation pathways in that case was different, depending on the diet the animal received. Less bio-hydrogenation of polyunsaturated fatty acids (PUFAs) was observed in the rumen when the animals were fed grass and the opposite in animals which were fed diets high in grain. These results, related to the role of protozoa in the rumen fatty acid metabolism, were the most important scientific achievement made within this project. The relation between fatty acid bio hydrogenation, the absence of protozoa and methane formation was also addressed in the last project stage. The absence of protozoa in the rumen resulted in 25 % less methane production and more bio hydrogenation of PUFAs. Over this two years' project a wide group of DNA based techniques, such as DGGE, qPCR, T-RFLP, cloning and sequencing, were optimised to study and quantify the different microbial population inhabiting the rumen involved in bio hydrogenation and methane production, namely bacteria, protozoa and archaea.

Data: CORDIS, © European Union