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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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Methionine Requirements for Lactating Sows - Cierra Kozole

Video: Methionine Requirements for Lactating Sows - Cierra Kozole


In this episode of The Swine Nutrition Blackbelt Podcast, Cierra Kozole, PhD candidate in Swine Nutrition at the University of Guelph, explains how methionine supports lactating sows beyond milk protein synthesis. She discusses updated requirement estimates, source comparisons, methylation demand, and why modern sow genetics may require more precise amino acid strategies. Listen now on all major platforms!

"Methionine supports protein synthesis while also serving critical functions through methylation pathways that influence multiple biological processes."

Meet the guest: Cierra Kozole / cierra-kozole-772b64253 is a PhD candidate in Swine Nutrition at the University of Guelph in Canada. Her doctoral research focuses on refining estimates of methionine requirements for primiparous lactating sows, including evaluating methionine sources, nutrient partitioning, methylation reactions, and the links among amino acid supply, milk production, and sow protein retention. Learn more from Cierra Kozole on The Swine Nutrition Blackbelt Podcast, available on all major platforms.