Grass Tetany Merry-Go-Round 

D. E. Larsen, DVM

I pulled into Boeckel’s driveway off Old Holley Road and expected to find Rein, but there was no sign of anyone. I was heading to the house when I saw Rein coming around the barn on his tractor.

“I thought I had misunderstood you for a minute,” I said as Rein brought the tractor to a stop beside my truck.  

“After I got to thinking about things, I figured I better get the tractor to take you out to the cow,” Rein said. “She is down on the far side of this pasture that I farmed and seeded this year. It is pretty lush right now and a little damp. You can throw your stuff on the back here and climb up beside me, and we will be off. That way, we don’t have to worry about your truck getting stuck on the hillside.”

All loaded, we headed out through the new pasture. The grass was lush and probably close to what could be called knee-deep. The cow, a black-baldy, was down and struggling to get up when we pulled up beside her.

“This is probably grass tetany,” I said. “She just has had a little too much of this pasture.”

“So, what am I suppose to do with all this grass?” Rein asked. 

“Let’s look at her first and make sure I am talking to you about the right stuff,” I said. “If this is grass tetany, we need to be pretty gentle with her. Some of these gals will be on the fight when they finally get on their feet. And with her horns, we don’t want her after us.”

Rein watched as I examined the cow. I collected a blood tube for testing at the clinic. Then I started an IV with a combination of a calcium and magnesium infusion. 

“This has to go slow,” I said. “I think you must have found her pretty early. She doesn’t look too bad. I would guess she will be up after this one bottle.”

“Why the blood?” Rein asked. 

“That is just insurance,” I said. “The diagnosis is usually confirmed with a favorable response to treatment. But sometimes, these cows will be down for a day or two. If she doesn’t get right up, I will have a sample to check to make sure of the diagnosis.”

“I am not sure I understand what is wrong with her.” Rein said.

“Grass tetany is caused by a low magnesium level in the blood. Most of the time, there are also some other minerals below normal. Calcium and sometimes potassium is often low. I’m not quite sure, but I think the lush pastures just washes everything through the gut, so those minerals are not absorbed.”

“How do I prevent it? Rein asked. “I mean, I have all his damn grass, and I hear you say that is the cause.”

“Like your mother probably told you, all things in moderation,” I said. When I was a kid, we would string off a narrow section of a new field with an electric fence. Then every day, move the fence ten or twenty yards, giving the cows a new section. They make better use of the grass that way, concentrating their grazing to a small area, and there is not enough grass to cause a problem like this cow suffered.”

“That might work. That way, I am not out there chasing cows out of the field after a couple of hours,” Rein said.

I finished the IV infusion and started putting up my stuff. After I had everything back on the tractor, I planned to give the old cow a good slap on the butt to see if she would get up right away.

“Sometimes, these gals are on the fight when they first get up,” I said. “You might want to crawl up on the tractor before I roust her up.”

I still had the nose tongs in my hand.  I went over and slapped her across the butt with a loop of the rope. That proved to be a bit of a mistake.

She scrambled to her feet and let out a bellow. Then she turned, bucked a couple times, and came charging at me. I turned to seek refuge from the tractor and almost knocked Rein down. He obviously was not on the tractor.

We started around the tractor, and luckily, it took a few seconds for the cow to negotiate the corner around the front of the tractor. This gave us time to get to the opposite side of the tractor.

It didn’t take her long to get her bearings and come around after us. We were able to keep the tractor between us. The cow was bucking and snorting as she chased us around and around the tractor. This wasn’t going to turn out well if we didn’t get up on the tractor.

“Rein, you get up on the tractor on the next turn,” I said. “I will give her a slap across her nose with the rope and slow her down enough to give you time.”

I stayed at the front of the tractor, and Rein was back trying to climb up into the seat when the cow came around the corner. I slapped her across the nose with the rope. That stopped her for a moment, and I made a mad dash to get up on the tractor.”

“That’s the most excitement I have had in a while,” Rein said. “What caused that?”

“That’s a first for me, but they say that it is common for these cows to come up on the fight,” I said. “Let’s just drive out of here, and she will calm down if she is left alone for a couple of hours.”

“Do I need to do anything for her?” Rein said.

“You give her a couple of hours and then drive her into the barn,” I said. “She needs to be on dry hay for a couple of days and some extra magnesium in her minerals. I would play it safe. I would herd her with the tractor. Don’t walk out there on foot.”

“I have some minerals set out, but I am not sure they spend much time at the box.”

“You need to check that it has some magnesium in it. I think you could probably get a few magnesium blocks from Stan. They might use a new block better than a mineral box that has been out there all spring.”

Rein got a half dozen new mineral blocks with high magnesium and ran an electric fence across the pasture to portion it out. He never had any other problems. I remain thankful that he took me out to the cow on the tractor. I am not sure what would have happened if we had walked out there.

Photo by Bulat Khamitov from Pexels.

Published by d.e.larsen.dvm

Country vet for over 40 years in Sweet Home Oregon. I graduated from Colorado State University in 1975. I practiced in Enumclaw Washington for a year and a half before moving to Sweet Home to start a practice.

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