Methane is a product that contributes to the elimination of hydrogen from the rumen during the fermentation of the glucides. Its production is energy-consuming for the animal but can be limited by specific means or by adequate systems of livestock management. Several methods have been tried (though not yet applied at an agricultural scale) with the aim of reducing the production of methane : additives that inhibit the methane-producing microorganisms or modify the metabolic pathways in the rumen ; biotechnological trials (selection of rumen microorganisms or vaccination against the methane-producing microorganisms). When the amounts ingested by the animal increase and when the feed is rich in concentrates (and therefore poor in cell-walls) or in poly-insaturated fatty acids (linolenic acid), the production of methane diminishes. Intensified rearing methods result in a noteworthy reduction of the methane production per unit of animal product (kg milk or kg meat). This real possibility with an immediate effect goes however against the general trend where public opinion favours more extensive farming with high-quality products, the maintenance of the lands, and the preservation of the environment.