The project focuses on the poorly understood microbial 22:6n-3 biohydrogenation in the rumen. Extensive biohydrogenation occurs in vivo, but in vitro culture conditions had to be optimized to allow 22:6n-3 metabolism and identification of rumen biohydrogenating bacteria, both with pure and mixed cultures, the latter using the dilution-to-extinction approach. Finally, products formed during 22:6n-3 biohydrogenation are being identified using mass spectroscopy.