Effect of forage /concentrate ratio and soybean oil supplementation on in vitro fatty acid profile of sheep rumen liquor.

In an in vitro trial, the effect of forage/concentrate ratio (F/C) and soybean oil (SO) supplementation on rumen liquor fatty acids profile was studied with the aim to evaluate changes in the profiles of biohydrogenation intermediates during the fermentation process. Feed samples of four diets were inoculated with sheep rumen liquor: i) high F/C and no SO; ii) high F/C and SO; iii) low F/C and no SO; iv) low F/C and SO. Fermentation times were 6, 12 h. Trans fatty acid were formed when oil supplement or a low forage content were present in the diets, but at different times of fermentation, as a consequence of a shift from the usual rumen biohydrogenation pathway. In fact, when a higher forage percentage was included in the diet, the alternative pathways of rumen biohydrogenation did not occur; trans10 C18:1 concentration was low and neither trans10, cis12 CLA nor trans, trans CLA appeared.