By Greg Goodell, DVM, The Dairy Authority
When bird flu strikes your dairy, it quickly makes its presence known. Infected cows stop producing milk, herd rumination time dramatically drops, dry matter intake plummets, and the hospital pen overflows with cows that don’t look good.
Physical examination reveals a “dead” rumen with no rumen contractions occurring, high fevers (often >105°F), and teary/watery eyes or full-scale conjunctivitis. Affected cows just look extremely bad.
During the initial weeks of the outbreak, almost every day after treating cows with supportive care, I heard producers say the cows looked so bad they were not sure they would make it through the night. But we have found that dairy cows are extremely resilient! With supportive treatments, death loss has averaged just 1-2% of infected adult cows in Colorado.
Bird flu seems to start in mid-lactation cows. That is where you will find your first clinical cases. From there it spreads to cows up and down the lactation curve. Eventually you will have cases in all stages of lactation. Bird flu can also occur in dry cows which often causes abortions.
Once bird flu arrives on a dairy, it will travel through the entire herd—regardless of what you do to prevent it. Separating out clinical cows may reduce daily labor for treating cows by slowing down the number of treatments each day, but it also tends to prolong the length of the outbreak in the herd.
You can expect to treat about 2-3% of the herd each day. Over the course of the next 6-8 weeks about 15-25% of the herd will need supportive treatment. The majority of treatments will be needed during the first two weeks after bird flu is found at the dairy. Treatments need to be simple and fast. Extra labor will need to be pulled from other areas of the dairy to help treat cows because there will be a lot of cows to treat each day. (For more on how to prepare for bird flu, please see the blog “How to Prepare for HPAI at Your Dairy.”)
Supportive care is the key to helping cows recover. Treatment goals are simply to rehydrate and reduce fever. In our practice, we have experienced that approximately 10% of all cows clinically affected will be classified as severe cases. The other 90% will be mild cases.
For cows classified as mild, without a fever, we treat those like an indigestion case —
fluids, probiotics and antipyretics to reduce fever if needed. Cows with high fevers are classified as severe and treated like pneumonia cases. They receive fluids, probiotics plus antibiotics and antipyretics to reduce fever. All cows should be monitored daily, with health information for each recorded in herd management software for tracking. Treatments should be repeated until cows recover. Generally, about 3-5 days depending on severity and how the cow responds.
Once the first clinical case is found in a herd, the number of cases continues to grow and peaks at about 10 days. At approximately 14-16 days after the initial case the number of new cases of bird flu starts to drop quickly. But new cases can linger and continue to occur 3-4 weeks from initial onset.
The good news is that most cows that get bird flu do recover. But when a herd becomes infected, it takes an intentional management effort and dedicated employees caring for and delivering supportive treatment to a lot of cows each day.
