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U.S. Department of Agriculture detects second bird flu strain in dairy cattle

U.S. dairy cattle tested positive for a strain of bird flu that previously had not been seen in cows, the U.S. Department of Agriculture said on Wednesday, ramping up concerns about the persistent spread of the virus.

The H5N1 virus has reduced milk output in cattle, pushed up egg prices by wiping out millions of hens, and infected nearly 70 people since April as it has spread across the country.

Genome sequencing of milk from Nevada identified the different strain, known as the D1.1 genotype, in dairy cows for the first time, the USDA said. Previously, all 957 bird flu infections among dairy herds reported since last March had been caused by another strain, the B3.13 genotype, according to the agency.

Reuters reported news of the detection of the second strain on Wednesday ahead of USDA’s announcement.

The second strain was the predominant genotype among wild birds this past fall and winter and has also been found in poultry, the USDA said. It was identified in dairy cattle through an agency program that began testing milk for bird flu in December.

“We’re seeing the H5N1 virus itself be smarter than all of us,” said Beth Thompson, South Dakota’s state veterinarian.

“It’s modifying itself so it’s not just staying in the poultry and the wild waterfowl. It’s picking up a home in the mammals.”

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Genetics vs Genomics in Swine - Dr. Max Rothschild

Video: Genetics vs Genomics in Swine - Dr. Max Rothschild



In this episode of The Swine it Podcast Show Canada, Dr. Max Rothschild, Distinguished Professor at Iowa State University, explains how genetics and genomics have transformed swine production. He explores genomic selection, key gene discoveries, and the role of gene editing in improving disease resistance and productivity. Practical insights on litter size, meat quality, and industry adoption are also discussed. Listen now on all major platforms!

"Genetic improvement in swine production accelerated significantly once molecular tools enabled identification of DNA level variation influencing growth, reproduction, and meat quality across commercial populations."

Meet the guest: Dr. Max Rothschild / max-f-rothschild-b3800312 earned his PhD in Animal Breeding from Cornell University and has spent over four decades at Iowa State University advancing swine genetics and genomics. His research focuses on genetic improvement, disease resistance, and molecular tools for swine production. A leader in pig genome research, his work has shaped modern breeding strategies.