600516 Disclosed is a method for reducing the production of methane emanating from the digestive activities of a ruminant and or for improving ruminant animal performance by using, as active compound at least one nitrooxy alkanoic acid and/or derivative defined by formula (I), which is administrated to the animal together with the feed. Also disclosed is the use of these compounds in feed and feed additives such as premix, concentrates and total mixed ration (TMR) or in the form of a bolus