Effect of Unconventional Oils on in Vitro Rumen Methane Production and Fermentation

The effects of unconventional oils high in polyunsaturated fatty acids (PUFAs) (blackberry, blueberry, raspberry, pomegranate, black seed and hemp oils) on in vitro rumen fermentation and methane (CH4) production were examined in a 24-h batch culture experiment. Treatments consisted of a control (no oil supplement), a control plus corn oil, or a control plus the unconventional oils. Oils were added to rumen cultures at 500 mg L-1 (equivalent to 3.3 g oil.kg-1 of dietary dry matter (DM)). After 24 h of incubation, CH4 production was not different between the control and the corn oil treatment. Of the six unconventional oils tested, only the hemp and blueberry oils reduced CH4 production by 10-16% relative to that of the control and corn oil treatments. Dry matter degradability and total volatile fatty acids (VFAs) were not affected by the addition of oils. Except for a reduction in the acetate concentration with the raspberry and hemp oils, all tested unconventional oils had no effects on fermentation and the VFA profile relative to those of the control. In conclusion, our results showed that hemp and blueberry oils were moderately effective in reducing rumen CH4 formation without compromising rumen fermentation and digestibility.