Biohydrogenation Pathway of α-Linolenic Acid in Rumen of Dairy Cow In Vitro.

The t 9, c 12, c 15-C18:3 as an isomer of α-linolenic acid ( c 9, c 12, c 15-C18:3; ALA), has been recently detected in milk, but has not been found in the rumen. This study hypothesized that it may be a biohydrogenation product of ALA in rumen and aimed to explore whether it was present in the rumen and help to understand the rumen biohydrogenation mechanisms of ALA. The in vitro experiment included two treatments, a control check (CK group) with 50 µL ethanol added, and ALA group with 50 µL ethanol and 2.6 mg ALA (ALA addition calculated by 1.30% of dry matter base of diet); each sample of fermentation fluid had the composition of C18 fatty acids analyzed at 0, 0.5, 1, 2, 3, 4, 5, and 6 h. The results showed that no t 9, c 12, c 15-C18:3 was detected in the CK group, but ALA addition increased the concentration of t 9, c 12, c 15-C18:3 in fermentation fluid. The content of t 9, c 12, c 15-C18:3 peaked 1 h after fermentation, then declined gradually. At 1 h, no t 9 c 12 c 15-C18:3 was detected in the fermentation fluid of the CK treatment. The results suggested that ALA converted to the isomer t 9, c 12, c 15-C18:3 through biohydrogenation in the rumen. The addition of ALA can also increase the concentration of t 9, c 12-C18:2, c 9, t 11-C18:2, c 12-C18:1, t 11-C18:1, t 9-C18:1, and c 6-C18:1 in fermentation fluid. It was concluded using an in vitro experiment that t 9, c 12, c 15-C18:3 was a product of rumen biohydrogenation of ALA.