Potentials of using dietary plant secondary metabolites to mitigate nitrous oxide emissions from excreta of cattle: Impacts, mechanisms and perspectives

Nitrous oxide (N(2)O) is a potent greenhouse gas as well as the key component depleting the ozone sphere of the earth. Cattle have high feed and water intakes and excrete large amounts of urine and feces. N(2)O can be produced from cattle excreta during storage and use as fertilizer. Mitigating the N(2)O emissions from cattle excreta during production is important for protecting the environment and the sustainable development of the cattle industry. Feeding cattle with low-protein diets increases N utilization rates, decreases N excretion and consequently reduces N(2)O emissions. However, this approach cannot be applied in the long term because of its negative impact on animal performance. Recent studies showed that dietary inclusion of some plant secondary metabolites such as tannins, anthocyanins, glucosinolates and aucubin could manipulate the N excretion and the urinary components and consequently regulate N(2)O emissions from cattle excreta. This review summarized the recent developments in the effects of dietary tannins, anthocyanins and glucosinolates on the metabolism of cattle and the N(2)O emissions from cattle excreta and concluded that dietary inclusion of tannins or anthocyanins could considerably reduce N(2)O emissions from cattle excreta.