Elizabeth Doughman, editor, WATT PoultryUSA and Poultry Future: Hello, I’m Elizabeth Doughman, the editor of WATT PoultryUSA and Poultry Future.
This Future of Poultry Podcast is brought to you by Elanco. Elanco Animal Health Incorporated is a global leader in animal health dedicated to innovating and delivering products and services to prevent and treat disease in farm animals and pets, creating value for farmers, pet owners, veterinarians, stakeholders and society as a whole.
The Elanco poultry team works closely with producers and integrators to deliver comprehensive, data-driven solutions that support bird health and production goals. Through a combination of technical expertise and on-farm support, Elanco helps customers safeguard flock well-being while supporting long-term operational success. Learn more at www.elanco.com.
Joining us today is Dr. Claudia Osorio, associate advisor at Elanco, to discuss anticoccidial sensitivity testing or AST and how producers can use it to help with the decision-making process when choosing which anticoccidials to use for coccidiosis control programs.
Thanks for joining us, Claudia.
AST has been around for decades, but expectations have changed as production systems, products and pressure on performance have evolved. From your perspective today, how do you define a ‘good’ anticoccidial sensitivity test?
Dr. Claudia Osorio, associate advisor, Elanco: A good AST is one that generates reliable field relevant data by accurately evaluating how a farm’s current Eimeria isolates respond to a specific anti-coccidial drug program. When aligned with field observations, it becomes a valuable tool for guiding effective coccidiosis control strategies.
Doughman: What are the non-negotiables in isolate collection, design and endpoints to make the results decision-worthy for a complex?
Osorio: The biggest non-negotiable is that the isolates represent the Eimeria population circulating the complex, not just one problem flock. That means collecting isolates across different performance levels in the complex from used litter, not new litter. Because I want an oocyst population that reflects real field exposure from births in the active cycling window, which is typically 21 to 28 days of age, but if there is a concern about early breakdown. I will also include younger birds around 14 to 18 days of age. Also, when collected, focusing on the feed and water lines and the center of the house when bird activity is highest.
The trial design also matters. Proper controls including an unmedicated challenge control and, when possible, a non-challenge control. All product tested at labeled dose using sufficient replication, typically eight to 12 pens per treatment with 20 to 30 birds per pen. Product selection should include the current program and the most realistic alternatives. Be careful about how products are grouped. Ionophores and chemicals behave very differently in ASTs.
Finally, the right endpoints are critical. Performance data, weight gain, feed conversion, mortality and uniformity, along with a species-specific lesion score using a standardized system. We also need some measure of intestinal cycling or gut integrity where that oocyst output or semi quantitative assessment.
At the end of the day, we need both pathology and performance to make confident program decisions at the complex level.
Doughman: One of the most challenging parts of AST is interpreting results that may be unclear, especially when lesion scores, cycling data and performance don’t all tell the same story. When you look at AST data, how do you interpret partial sensitivity or conflicting signals?
Osorio: Never interpret AST data in isolation or based on a single number. When I interpret partial sensitivity, I think in terms of a traffic light system. Green means good sensitivity, where performance is closed to the non-challenge control and lesion scores are clearly reduced. Red is poor sensitivity where performance looks like the challenge, control and lesion scores remain high. Partial sensitivity usually sits in the yellow zone where performance is partially protected and lesion scores are moderate.
Doughman: What specific patterns tell you if it’s time to change programs?
Osorio: When it comes to changing a program, it is rarely about one number or one bad flock. It's about patterns. Seeing the same lesion trends, especially increasing in Eimeria maxima across multiple forms or health checks, increasing cycling seen on scrapes. When those findings line up with softer performance drift and appear across several farms, not just one house, that is usually a program level issue. When multiple signs repeat across the complex, we recommend changing the program
Doughman: As more integrators move back and forth between NAE and NAIHM systems, the role of AST can look very different depending on the program in place. How have these fluctuations changed when AST is most useful and how should producers think about interpreting AST results differently in NAE versus NAIHM programs?
Osorio: AST is useful in both systems, but for different reasons.
In NAE systems, AST is most decision worthy. Because it is focused on chemical products, including weak chemicals, those products can lose sensitivity relative quickly. AST helps detect early shifts before performance problems become obvious.
In NAIHM systems, interpretation depends heavily on product class. Ionophores reduce most, but not all, coccidia. Allowing control leakage and immunity development so ionophores can sometimes appear to look weaker because ASTs are short duration tests. That means ionophore AST results always need a strong field context. Strong chemicals are where AST is powerful because when resistance develops, performance drops fast, and AST mirrors that clearly.
Overall, AST today is not about finding a single answer or ranking products in isolation. It is about tracking sensitivity trends over time, especially for chemicals that that can lose effectiveness quickly. And using that information together with field lesions, scraping and performance to support inform long-term program decisions in both NAE and NAIHM systems.
Doughman: AST can be a powerful tool, but only when used correctly. To wrap things up, if you could give integrators one or two practical ways to implement anticoccidial sensitivity testing well, so they avoid overreacting to a single AST report but still act in time to protect performance, what would those be?
Osorio: First treat AST as part of a standard decision framework, not a one time emergency test. That means having clear guidelines for when to run it, collecting isolate in a consistent and representative way and interpreting results alongside field lesions, cycling performance, strength and management changes.
Second, be intentional about what you test and why. Ionophores and chemicals behave differently. They should be evaluated with different expectations.
AST work best when it is used to answer specific questions, especially around chemical sensitivity and rotation timing. When used this way. AST helps integrators avoid knee-jerk reactions while still making timely program decisions to protect performance.
Doughman: Thank you so much for sharing these insights. For more information on the solutions discussed here today, visit Elanco Animal Health at www.elanco.com.
Thanks again, Claudia, and thanks to you for tuning in.
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