Editor's note: The following case study was provided by Don Clark with Standard Nutrition in Hewitt, Wis.

This past December, one of the dairy farms that Don Clark works with wanted to give its fresh cows an edge and started drenching them. This dairy farm milks about 300 cows and has an average milk production of more than 80 pounds.

“The owner had picked out a drenching product that other dairymen in the area had been using with some success,” says Clark.

Shortly after the herd started drenching its fresh cows, one of the cows dropped dead. Obviously, the dairymen was concerned and wanted to know why this animal had died.  “On initial investigation, we found nothing out of the ordinary and assumed the person pumping the cow got some of the fluid mixture into the lungs,” explains Clark.

As time went by, a few more cows died after being drenched. Cows would die anywhere from 15 minutes to an hour or two after being pumped; the average time was 30 minutes when the cow would drop over dead.  The herd was not seeing the typical signs of respiratory distress expected when getting fluid into the lungs.  Instead, cows appeared relatively normal until they dropped.

The feeding program, drenching protocol and cow-handling were all reviewed, revealing nothing. Clark decided to go back to the product and see if there was something he was missing. “The ingredient list on the tag looked fine. But, as I was reviewing the tag I saw another bag out of the corner of my eye.  After examining this bag, I discovered it was an open bag of potassium chloride,” explains Clark. “We weren’t feeding potassium chloride in any of the rations, so there was no reason it should have been there.”

What Clark discovered is that potassium chloride had been added to the drench. This information had never been shared with him before.

After reviewing the mixing procedure for the drench, Clark learned that the farm had been using three cups of the drench product in 5 gallons of water, which was the recommended mixing rate on the tag. Then, the dairy was adding one cup of potassium chloride. The herd manager had then increased the potassium chloride to two cups in the drench mix.

“I immediately contacted my colleagues to confirm proper dosing levels for potassium chloride,” notes Clark.  With a quick internet search and with information gleaned from Jesse Goff, professor of biomedical sciences at Iowa State University, it was determined that 110 grams or a little less than 4 ounces was the maximum amount of potassium chloride that should be fed to a cow. If more is used, it could be cardio-toxic and stop the cow’s heart.

After getting a digital scale and weighing the cup the dairy farm was using to measure the drench ingredients, Clark discovered that the cup was actually 11 ounces instead of the 8 ounces that had been assumed. So, this herd was effectively feeding more than 20 ounces of potassium chloride. This was at least 16 ounces more than the cow could withstand, and this level of potassium chloride was killing cows.

Clark says he asked the dairy farmer where he got the idea to feed potassium chloride, and he said that someone had told him to feed it. “It’s unclear  the amount that was originally suggested, but the dairy decided to increase the amount fed on their own, up to 2 cups, which in this case was more than 20 ounces,” says Clark. “He probably thought if a little was good, a lot would be better.”

As soon as the potassium chloride was eliminated from the drench, cows stopped dying. Every animal drenched since then has been fine.

“It was a tough lesson,” notes Clark. “It was a misuse of a product and miscommunication.”

The dairy farmer will be more careful about who he listens to.  When he comes up with a new idea, it’s advised that he ask a number of people before implementing it.  And, Clark says “everything this particular farm does from now on is going to be written, including all recommendations received.”