What is in this article?:
- Research by a veterinary pathologist indicates salt is a big factor in preventing and treating grass tetany.
- Without adequate sodium in the blood, the body grabs onto the most available cation, which would be magnesium, followed by calcium.
- 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.
A change in condition
Swerczek’s training includes veterinary medicine and comparative and nutritional pathology. As a pathologist, he did diagnostics and necropsies on livestock until the early 1970s. Then, he worked as an equine diagnostic research pathologist for 15 years.
In 1986, his necropsy research moved to all classes of livestock. Upon resuming necropsies on cattle, he was shocked to see how much worse the grass tetany situation had become during his hiatus.
“The dead cattle were arriving in a wasted condition I hadn’t seen before 1971, when I’d stopped doing cattle necropsies.” Then, in 1995, he began to see cattle with adult salmonellosis, coccidiosis and other calfhood diseases, which didn’t make sense.
Some pathologists observing the poor condition of cattle coming in for necropsy thought producers weren’t feeding enough protein, Swerczek says. “But when grass tetany problems peaked in 1995-96, the purebred breeders were hit the hardest. So, I began evaluating mineral mixes and visiting some of these purebred herds.”
Swerczek collaborated on this project with William McCaw, a DVM searching for answers in several purebred herds. McCaw also had surmised that something related to diet was causing wasting and opportunistic diseases, he says.
McCaw and Swerczek convinced a handful of producers to stop feeding high-mineral, low-salt mixes in order to serve as a control in their observations. When Swerczek started looking at herds throughout the state, he found a Hereford-Simmental crossbred herd whose owner was feeding loose salt rather than the conventional high-mineral, low-salt mix. (This herd was healthy and did not show any signs of wasting like the cattle on surrounding farms.)
“He still used salt houses – little run-in sheds with a feedbunk for loose salt, to keep it out of the weather. Most farmers had moved from loose salt to mineral mixes and salt/mineral blocks,” Swerczek says.
But this rancher had a salt house in every pasture, and wasn’t supplementing magnesium. “He’d been in the cattle business more than 40 years and never had a case of grass tetany,” Swerczek recalls. Was this an indicator that perhaps supplemental magnesium wasn’t needed to prevent grass tetany?
Later, several herds that stopped feeding the high-mineral, low- salt mixes quickly started to turn around. “Most of the cows had diarrhea and were wasting away. But, within 24-48 hours of giving them loose salt, the cattle improved,” Swerczek says.
In particular, Swerczek recalls working with a 1,000-head Angus herd at that time. Driving across the farm with its manager, Swerczek says they encountered a cow that had been down for several days despite multiple treatments with magnesium and calcium. Swerczek had some sea salt, and put it in front of the cow.
“The manager went back three hours later and that cow had gotten up and wandered off. She went down again, however, so he put more salt in front of her. He went out the next morning and she’d gotten up and rejoined the herd,” Swerczek recalls.
Elsewhere in the herd, other cattle were showing signs of grass tetany and going down. “I told the manager to put a handful of salt in front of them or get it into their mouths to see what happened; they all came out of it. So, I asked if he’d be willing to take away high-mineral, low-salt mixes and replace it with high-salt, trace-mineral mixes. He agreed to try it with a small group confined in a separate pasture. The next cold spell, the cows with access to high-salt, trace-mineral mixes were unaffected by tetany, while the other cattle were affected.”
In the late 1990s, Swerczek says he visited a farm where cattle were dying in one pasture but not another. The owners had purchased 800 yearlings and pastured half on a farm they owned, with the rest on an adjacent rented farm. On their farm, which featured fertilized clover, the cattle died the following spring, but there were no deaths on the rented pasture across the fence.
“In analyzing the pasture, I found high nitrate and extremely high potassium in the fertilized plants. At first, I thought the problem was related to potassium; later, experiments showed it was a combination of potassium and nitrate.”