How feasible is it to replace urea with nitrates to mitigate greenhouse gas emissions from extensively managed beef cattle?

Abstract

Reducing methane emissions from cattle in Australia will be dependent upon finding a strategy that can be readily adopted by its northern beef industry. The majority of the herd are located in this region and they graze low-quality tropical (C4) pastures, resulting in high methane output. There are few mitigation options that can be readily applied to extensively grazed cattle. The addition of nitrate to the diet of cattle has been shown to reduce methane production and may be an applicable strategy in northern Australia. Nitrogen is often the primary limiting nutrient in low-quality tropical pastures and it is common practice by industry to supplement with urea. Supplying an equivalent dose of nitrogen using nitrate as an alternative to urea has been demonstrated in cattle without adverse impacts upon animal productivity or health. These findings may not be directly applicable to grazing cattle in northern Australian because the diets and feeding management are not representative of the region. Nitrite toxicity can result from feeding nitrates to livestock and there is evidence that the composition of the total diet and feeding pattern influences the risk of toxicity. If nitrate supplementation in grazing beef cattle in northern Australia can be demonstrated to reduce methane and be applied safely, adoption rates will still depend on carbon market pricing. Current modelling suggests that the cost of supplementing beef cows with nitrate in northern Australia would be at least double the cost of urea supplementation.