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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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Assessing Welfare Resources During Late Finish - Dr. Anna Johnson & Emma Coursey

Video: Assessing Welfare Resources During Late Finish - Dr. Anna Johnson & Emma Coursey


In this episode of The Swine Nutrition Blackbelt Podcast, Dr. Anna Johnson from Iowa State University and Emma Coursey from the University of Illinois discuss research evaluating welfare resources during the late finishing stage on commercial swine farms. They explain how feeder management, water use, space allocation, and pig health influence welfare outcomes and practical on-farm management. Listen now on all major platforms!

"Small resource issues can become larger welfare problems when multiple stressors interact across finishing barns."

Meet the guests: Dr. Anna Johnson / anna-johnson-05028a14 is the Morrill Professor of Animal Behavior and Welfare at Iowa State University. She earned her Ph.D. in Animal Sciences from Texas Tech University and completed her master's degree in Applied Animal Behaviour and Welfare at the University of Edinburgh. Her research focuses on practical solutions that improve farm animal welfare, including sow productive lifetime, animal-human interaction, environmental enrichment, and Precision Livestock Farming.

Emma Coursey / emma-coursey-183810241 is pursuing a Doctor of Veterinary Medicine degree at the University of Illinois College of Veterinary Medicine after earning a bachelor's degree in Animal Science from Iowa State University. Her academic interests include swine health, production, and animal welfare, with research experience evaluating welfare resources in commercial finishing pigs.