Elizabeth Doughman, editor, WATT PoultryUSA and Poultry Future: Hello, I’m Elizabeth Doughman, the editor of WATT PoultryUSA and Poultry Future.
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In today’s episode, my guest is Dr. Scott Gustin, U.S. poultry technical leader for Elanco.
Thanks for joining us today, Scott.
What effect do seasonal changes have on management and coccidiosis control?
Dr. Scott Gustin, U.S. poultry technica leader, Elanco: Typically seasons influence conditions in the house by how much water or moisture is deposited, and then how much can be removed through ventilation.
More moisture in general means more sporulation of oocysts and more proliferation of bacterial challenges, but it's easy to say that certain times of the year give certain conditions. If you're in South Central U.S. broiler production right now, humidity's low, the highs are in the 80s and you'd say we're almost experiencing summer-like temperatures in the fall so moisture's easy to remove. You can keep litter dry. And really this is a favorable environment for managing coccidiosis, provided everything else in the program stays the same.
It won't be long before cooler temperatures will start to set in. We'll have more ambient humidity. Then, Mother Nature is going to allow for better growth rates and efficiencies but, at the same time, litter, moisture, and cocci overall disease challenges can be greater that time of year. Clostridial diseases tend to favor larger animals in a population. And more pounds at the same age in a chicken house of chicken also means management must be really on the top of their game.
Typically, as far as seasons goes, ambient humidity is the one of the greatest challenges for producers out there.
Doughman: You guys have recently done a fairly large analysis of HTSi data looking at seasonal changes. What have you found?
Gustin: Well, we looked at over 10,000 flocks in our HTSi database, which is a health tracking system database from 2021 through midway of 2025. Really this is building on some work that Lynn Warren and Francene Van Sambeek have presented before.
We split the year into astronomical seasons, so winter was December 21st through March 20th. Spring is March 21st to June 21st. Summer is June 22nd to September 21st and fall being September 22nd to December 20th.
We looked at one really big parameter that I would say most consider the most impactful cocci species and best way of evaluating it, and that being microscopic Eimeria maxima. I had some curiosity just to see if we've changed things in our bird sizes and our cycle length has gradually gotten longer. Maybe there's more cool cell usage in summer that might affect seasons and greater incidents of microscopic maxima.
Conventional chicken wisdom would typically say that maximum levels would be lower in the summer and winter would be the highest. And our data did prove that they were. What was striking is that the differences, although statistically significant, were relatively small. So Summer is not necessarily where the living is easy.
Any longer summer incidents of average microscopic maxima was only 8% lower than in spring and fall. Winter, which we thought would be the highest incidence was only 2% higher than spring and fall. The same was true for average score, but again, very small differences. Typical score during spring and fall, winter was 0.4 to and the only change was up to a 0.3 in the summer. This was regardless of which coccidiosis control program is being employed, the overall relationship still held true.
I guess, at the end of the day, we just can't take our eyes off the toddler at any time of the year when it comes to coccidiosis.
Doughman: What trends do we typically see reflected in the HTSi as we head into the cooler months? Is there a true “winter slide” when it comes to performance?
Gustin: Again, looking at some benchmarking data and really prior to last winter, because I think avian metapneumovirus (aMPV) really made for difficult conditions, high mortality and maybe wasn't the best baseline to measure against.
But the typical slide in performance from ideal growing conditions -- say birds settling in September – versus per poor performing months – like birds settling in March – you can really expect that winter slide to be just over six points of lost feed conversion. When you look at the top quartile producers, the change is not as great, but it's still five and a half points of feed conversion.
In the industry, we try and remove sources of variability through housing, nutrition, coccidiosis control. There's a still a big change in efficiency that we have to overcome and try as manage as best we can. Some of this variability, this winter slide will be obviously determined by where your location is.
I think the biggest takeaway is no matter where you're at, is knowing your typical slide in the winter and being aware of what what might need to be investigated further.
Doughman: So what are the biggest watch-outs for producers as winter takes hold, with regards to programs and husbandry?
When you look at benchmarking data, there's a lot of changes that occur in any given year, may have a breed change, ingredient values programs, new diseases, emerging diseases, etc.
First I think you have to recognize there is a problem. And I think you have to do that with good benchmarking internal and external data for your region. If you're in December-January and you've already lost eight points of feed conversion adjusted for weight, it's really time to critically look at your programs and develop an action plan.
It may be your winter temperature curve could be new change to a program you didn't have last year. You really need to go out and verify what is happening and is actually happening on the farms. Are your ventilation programs really accomplishing what they need to? If mortality is up during the winter, where is that mortality occurring? What value is that in terms of feed conversion?
But by the same token, if you've gotten four points worse, and it's in December, I would say that now isn't the time to go and throw the baby out with the bath water and really change every program. The key takeaway is knowing your normal because we make a lot of mistakes simply by overreacting and changing.
For the sake of change, last winter would not probably be the best but baseline for most complexes. It's always better to rely on good data where possible, and if we at Elanco can be a part of that data solution, please let us know.
Doughman: Thanks again, Scott, and thanks to you for tuning in. For more information on the solutions discussed here today, visit Elanco at www.elanco.com.
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