Nutritional strategies for reducing methane production by ruminants – A review

Methane a normal endproduct of nutrient fermentation in the rumen of ruminants not only affects on the environment but also on the economy of animal production. After carbon dioxide, methane is the second major green house gas contributing to global warming but methane is 20–40 times more potent as green house gas. It is impossible to completely stop methanogenesis in rumen as it is the integral component of rumen fermentation and essential but wasteful process. Various strategies suggested for reducing methanogenesis include decreasing number of ruminants, increasing non ruminant animals, genetic manipulation of ruminal methanogenic bacteria, development of less methane producing breeds and dietary/nutritional manipulations. Dietary manipulations seem to have significant potential in future because of its simplicity and practical feasibility. The nutritional manipulations for suppressing methanogenesis include provision of feed additives (chemicals, organic acids, probiotics), diets rich in unsaturated fatty acids (UFA), modification of feeding practices and supplementation of straw based diets with deficient nutrients. Antibiotics including ionophores reduce methanogenesis but their effects are short lived. Fats and oils can be used in medium amounts as these in large amounts can depress fibre digestion.