Swerczek reasoned that cows go down with grass tetany due to a
deficiency in magnesium and calcium, but he didn’t know why salt
worked. He then used horses as a research model because similar
nitrate-toxicity symptoms were seen in horses when grazing
frost-damaged pasture.  Swerczek began by feeding some horses
extra protein to raise protein and nitrogen levels in their
blood.   “We’d been taught for many years that nitrate isn’t
toxic; it’s only toxic if converted to nitrite. However, nitrate
in excess may be indirectly toxic if it interferes with the
magnesium and calcium metabolism,” he says.  The animal’s body
must eliminate excess nitrate and does this through the cations,
especially sodium, he adds.  “Without adequate sodium in the
blood, the body grabs onto the most available cation, which
would be magnesium, followed by calcium,” Swerczek explains.
When the cow consumes frost-damaged forage and the spike of
nitrate occurs, her body accesses magnesium in the blood to
eliminate the nitrate. This deplete