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.

“I knew nitrate was involved so I measured nitrate in their blood and put some of the horses on salt, and some on no salt. I found that without salt, the nitrate spikes. When horses had an adequate amount of salt, blood nitrate went down to very low levels,” he explains.

“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 depletes the body and the cow goes down.

“If there’s enough salt available, the body can grab onto the sodium and cows won’t go down with grass tetany. But, if you don’t have salt out on the day this hits, they go down. It must be there all the time, and it can’t be hard salt blocks because cattle can’t eat enough when they suddenly need it,” Swerczek says.

Another piece of the puzzle fell into place after Swerczek learned that some farms – despite having adequate salt out – were losing cattle; the cattle weren’t eating enough of it. The potassium level in grass was spiking after a hard frost, especially when it was lush and highly fertilized. Potassium was 15 times more than normal.

“Since the cations, potassium and sodium, are so close together, the body can’t always differentiate between them. People sometimes use ‘lite’ salt (half potassium chloride, half sodium chloride) to reduce sodium intake. These minerals can substitute for one another. When pastures are high in potassium, if there is nitrate in the damaged grass, they come up together as potassium nitrate,” he explains.

Swerczek theorized that when potassium spikes, even though cattle have salt available, they won’t eat it because the body thinks they already have enough sodium. The animals are actually sodium-starved. but their bodies can’t differentiate between excess potassium and too little sodium.

The body has the ability to keep sodium levels within normal range, but when it gets below that, you only have a few hours before that animal dies. “If you feed excess salt, however, and the animals eat it, they’ll be fine – as long as they have plenty of water,” he explains.