The present invention relates to a method for increasing the nutritional value of a vegetable material by subjection of a vegetable material to heating by means of radiation in the radio frequency range to achieve a temperature of between 110°C and 180°C, wherein the range of the radio frequency radiation is between 10MHz and 50MHz, and wherein an additive is added to said vegetable material before or during subjecting said vegetable material to heating. The present invention relates to a vegetable material having an improved nutritional value. The present invention relates to a use of the vegetable material as a feed for animals, preferably for ruminants. The present invention relates to a use of the vegetable material for preparing a mixed feed for animals, preferably ruminants.
