It seems spring has been slow coming, and with limited hay and feed supplies in the Plains, even cows are anxious for spring pastures to turn green. But a combination of cold winter/spring weather and older hay can come with a price tag.
Grass tetany might be easily defined as a deficiency of magnesium, but for Dick Kurtz of Oregon, Mo., it just means trouble. He lost three cows in March to the disorder and is carefully watching a few more.
“I’ve raised cattle for many years,” Kurtz says,” but this is a first in my lifetime to have issues with grass tetany.”
What Is Grass Tetany?
Although low blood magnesium levels (hypomagnesemia) are always involved with grass tetany, the disorder can occur under a variety of circumstances. Low levels of blood magnesium often come with low levels of blood calcium (also commonly called milk fever) in late pregnant cows and cows with calves at their side. These low levels mean that the muscles of the body cannot work properly, so the animal dies, as it cannot breathe.
The disorder can be complex, with many factors contributing:
- the age of the cow—older cows with young calves are most vulnerable;
- feeding on grass-dominant pastures and/or early crops;
- acid soils
- high-potassium soils and/or soils treated with potassium fertilizers;
- environmental effects such as:
- wind, rain and exposure
- sudden lowering of temperature.
What to Watch For
In northern Missouri, Kurtz says there were a few nights that the temperatures fell below 20 F, but the overly wet winter has caused the majority of the problem.
For many farmers, the first symptoms of the disorder are dead animals, and froth from the mouth and nose, after muscular spasms (tetany) for oxygen.
Mild symptoms include twitching of the animal’s face and ears, a wary appearance and a stiff gait. Lethargic movements, hard to get up and slow to move around, are typically noted. As the symptoms progress, cows might become more overly excited, galloping, bellowing and staggering in the pasture. Their front legs will also “goosestep.” At this point, cows could quickly go down on their side, with stiff and thrashing (leg paddling) and could die within minutes if they are stressed in any way.
Immediate Changes to Prevent Further Problems
With the help of his veterinarian, Kurtz is closely monitoring cows for the early signs. His veterinarian has administered several cows with IV solutions of magnesium and calcium to increase the level of the minerals in the blood stream.
“We first looked at the hay, thinking there might be toxicity in the hay or a poisonous weed, but that all checked out fine,” Kurtz says.
“The calves that were born were healthy and strong, but it seemed to affect the cows that hadn’t calved yet the most,” he explains. “I lost one, then two. Then I saw that others were lethargic, hard to get up and come to eat.”
Overall, his crossbred Hereford cows are in good condition, averaging 1,200 lb., and he’s one of the luckier farmers in his area to still have a supply of hay to get through April. Others are going to southern Missouri or Kansas to find enough hay to make it through spring.
His cows have been receiving a ration of grain since December, as well as red clover and brome hay.
“We did increase the corn and put a medication on the feed, after the diagnosis,” he says. “We’ve also switched to a free choice mineral with a higher magnesium level.”
Cows that are still to calve are at a higher risk, university Extension specialists say, as the gestating calf is also putting a strain on the cow’s blood system. See below for additional resources.
Producers should work with their veterinarian to develop a treatment plan, as a straight magnesium supplement is not always effective as a sole treatment. IV injections should also be done with a veterinarian assistance, as too much too quickly can kill the cow.
A “high-mag” mineral should be offered for several months or even more than a year to increase the cows’ natural mineral levels. Providing a higher energy and roughage diet is important, as well as moving lactating cows to higher legume and high dry matter pastures.
“We’re mostly blaming this on the wet, cold weather,” Kurtz says. “A week of warmer temperatures and sunshine would make a world of difference.”
Additional resources from Drovers and Bovine Veterinarian:
Editor's Note: In the spirit of full transparency, Dick Kurtz is the author's uncle.