Effects of Nitrate Supplementation on Nutrition, Performance and Methane Mitigation in Ruminants: A Review

Abstract

Nitrate supplementation is a viable option to mitigate enteric methane emission and also to improve animal performance. It is a well established fact that bacteria from the rumen are able to use nitrate as electron acceptors, instead of carbon dioxide and when nitrate is used as an alternative electron acceptor, methane production is reduced. The reduction of nitrate to ammonia, consumes eight electrons and each mole of nitrate reduced could thus lower methane production by 1 mole. In addition, to inhibiting methane production, the end product of nitrate production ammonia, is an essential nutrient for the rumen microbial population for protein synthesis and for the growth of microbial cells. Microbial protein in turn is the source of amino acids, absorbed and used for animal growth, reproduction and milk production. Urea, which is quickly converted to ammonia in the rumen, is often included in ruminant diets as a nitrogen supplement. The replacement of urea with nitrates in ruminant diets is feasible, subject to the management of nitrate supplementation. A further useful feature of nitrate supplementation is that, small amounts of nitrogen oxides produced during the nitrate metabolism in the rumen inhibit the activities of some methanogens, potentially increasing the level of inhibition of methane production where nitrate is only a proportion of the total fermentable nitrogen in a diet.