Encapsulated nitrate source may reduce cattle methane emissions

Cattle fed encapsulated calcium-ammonium nitrate produced 11% less methane than cattle fed urea.

September 30, 2020

2 Min Read
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The sulfur hexafluoride tracer technique allows scientists to measure the amount of methane emitted from the animal’s mouth and nose.Photo credit: Nicolas DiLorenzo

For several decades, researchers have been looking for ways to reduce the methane produced in the bovine rumen. New research by Nicolas DiLorenzo with the University of Florida and others shows that a small change to cattle diets can reduce the animals’ methane emissions by 11%. These findings are a step toward reducing greenhouse gas emissions from livestock.

The study was led by Darren Henry, a graduate from the University of Florida Institute of Food & Agricultural Sciences' (IFAS) College of Agricultural & Life Sciences who is now an assistant professor in the department of animal and food sciences at Texas Tech University. The study was part of Henry’s doctoral research directed by DiLorenzo and received funding support from the National Institute of Food & Agriculture.

The researchers discovered that cattle produced less methane when a supplement commonly given to grass-fed cattle was replaced with a supplement that provided the same nutrition but had different chemical properties.

“The rumen is where bacteria ferment the food the cow eats, helping break it down and allowing the cow to absorb more energy and nutrients from the food,” said DiLorenzo, an associate professor of animal sciences at the IFAS North Florida Research & Education Center.

Previous research has indicated that nitrates interrupt the chemical reactions that allow methanogens to produce methane. The University of Florida researchers wanted to test if feeding nitrates to cattle would have the same effect. In the experiment, they introduced nitrates by swapping out urea for encapsulated calcium-ammonium nitrate (eCAN).

“Diets of grass-fed cattle are often deficient in protein, so urea is used to supplement protein,” DiLorenzo said. “The thinking was: What if we used a different substance that would provide protein like urea does but had properties that would affect methane production?”

The researchers fed eCAN to cattle by mixing it into molasses, a traditional vehicle for urea, to ensure that the cattle would consume the eCAN provided.

“The eCAN looks like Dippin’ Dots ice cream and allows for the slow release of the calcium-ammonium nitrate in the rumen,” DiLorenzo said.

To measure how much methane the cattle produced when fed eCAN, the researchers used the sulfur hexafluoride tracer technique, which uses a U-shaped canister attached to a halter on the cow’s head. Small tubes connected to the canister sit above the cow’s nostrils. The device allows scientists to measure the amount of methane emitted from the animal’s mouth and nose.

Compared with cattle that were given urea, cattle that consumed eCAN produced 11% less methane, DiLorenzo noted, adding, “This is quite a large reduction and an exciting result.”

The study was published in Journal of Animal Science.

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