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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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Sow Welfare and Group Housing Systems - Dr. Laya Alves

Video: Sow Welfare and Group Housing Systems - Dr. Laya Alves



In this episode of The Swine it Podcast Show Canada, Dr. Laya Alves from the University of São Paulo, in Brazil, discusses how animal welfare regulations are evolving globally and their impact on pig production systems. She explains challenges in group housing, pain management, and euthanasia decisions, while highlighting the role of training and management in improving outcomes and economic sustainability. Listen now on all major platforms!

"Translating welfare requirements into daily farm routines without compromising economic sustainability remains one of the biggest challenges faced by producers globally today."

Meet the guest: Dr. Laya Alves / laya-kannan is a Postdoctoral Researcher at the University of São Paulo, Brazil, focusing on animal welfare in pig production, including pain management, euthanasia, and economic decision making. Her work integrates welfare science with practical farm management and sustainability. She collaborates globally to develop applied tools for producers.