Battling H5N1

FREEPORT, Minn. — June 15, 2024, was the start to a challenging and lengthy process for dairy farmer Chris Middendorf. While the initial outbreak of H5N1, aka bird flu, lasted 10-14 days, Middendorf said, the aftereffects are still being worked through.

“We did a pretty good job of keeping the barn full through it all,” Middendorf said. “We had such a big influx of cows calving. Now, in the last two months, because we struggled to get cows pregnant through the bird flu … my cow numbers were actually the lowest (this summer) because I had so many cows dry.”

Middendorf milks two separate herds on the farm — 385 cows in a 6-robot barn and 230 cows in a double-8 parallel parlor. The robot cows were infected with H5N1 first and then the virus transferred to the parlor cows roughly two weeks later.

“I was ending up with a bunch of cows in the separation pen (in the robot barn),” Middendorf said. “I started looking at them and I’m like, ‘What the heck is going on with these cows?’ and then, I was praying to God it wasn’t what I was thinking it was.”

He began to work with his veterinarian, Steve Baldwin, to confirm H5N1. Baldwin is at the farm weekly for pregnancy checks and was on site a few times to help with bird flu treatment protocols.

Throughout the battle, Middendorf said they were spending extra hours treating cows to make them feel better. He said the only medicine they found to break the temperature was dexamethasone, which could only be administered to non-pregnant cows.

Once Middendorf’s cows contracted bird flu, he noticed fevers and a drop in milk production. Middendorf said he lost about 26-27 pounds of milk on average. Middendorf previously had a 90-pound tank average, which did not come back until the end of May.

“We have to support (the cows) through the problem,” Baldwin said. “It did hit the majority, if not all, the cows very hard.”

Middendorf said some of the aftereffects they struggled with were mastitis, which led to 3-quarter cows, abortions and problems getting cows pregnant.

“I dealt with that issue of these cows (becoming) 3-teat cows or cows drying up on a quarter … for six months afterwards,” Middendorf said. “Every week I was putting 2-3 cows (on the list), making them 3-teaters.”

With the robot cows, Middendorf said the system would allow him to see the cows that were targeted by the virus on a specific quarter. The cow would have less milk time or production and a higher cell count or conductivity than usual on a quarter. This problem continued all the way through February, Middendorf said. After that, the problem slowed down.

In March Middendorf’s curiosity grew, so he checked the robot software to determine the number of cows he had only milking out of three teats post bird flu in the robot barn.

“There were 100 cows out of the 380 cows that were 3-teaters after all (the bird flu),” Middendorf said. “There were some in there to begin with, but there were probably 10 to 20.”

Throughout the aftermath of the virus, Middendorf also dealt with multiple abortions in milking and dry cows.

“We had probably 20 dry cows that maybe were dry two weeks and they were dumping calves,” Middendorf said. “Then we had a bunch of cows that were in lactation yet that were dumping them.”

Reproduction issues did not end there. He also struggled getting cows pregnant for almost two months after first contracting the virus. In late August and early September 2024, Middendorf said they had more luck with the cows settling.

After Middendorf tested positive for H5N1 in June 2024, he was assigned a case study manager and the state veterinarian put his farm in quarantine. Middendorf had to track where his cows went if any were sold during that time. All other processes continued as normal.

Also, after the first positive test, Middendorf said he had to sit down with two state vets and two epidemiologists to answer questions and gather information about the spread.

Fast forward to the end of February, when the mandatory bulk tank testing began in Minnesota. Middendorf learned his herd tested positive for H5N1 again. This time it was only in his parlor herd. After a couple weeks of testing, they were still positive for H5N1, so he decided to individually test each cow in the parlor herd to narrow it down.

As it turned out, it was one cow testing positive. Once he stopped milking her, the herd test came back negative.

During the second positive test, Middendorf started working with Marie Culhane, retired professor with the University of Minnesota. Culhane was conducting studies to gather more information and research H5N1 in cows. Culhane said one drop of infected milk is enough to kill 18,000 chickens.

“There’s just so much virus in that milk,” Culhane said. “Even if you washed off 99% … of one billion viruses, you still have 100,000 virus particles.”

The positive cow ended up going to Ames, Iowa, where researchers could test and gather information from her. She was ultimately euthanized and researchers gathered tissue samples for review.

“She never showed virus again in her milk (due to being dried off) or her nasal swabs, but she formed such a great immune response that her antibodies were able to recognize five or six different viruses,” Culhane said.

Culhane said researchers did notice the positive cow’s unmilked quarter had scar tissue destroyed by the virus. She said they are still working through the data they collected from Middendorf’s farm and the positive cow.