Improve broiler litter quality with increased air circulation

Using higher capacity circulation fans can help control litter moisture levels, leading to healthier flocks and better overall broiler performance.

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Maintaining drier broiler litter leads to better animal welfare and flock health. | Terrence O'Keefe
Maintaining drier broiler litter leads to better animal welfare and flock health. | Terrence O'Keefe

Using higher capacity circulation fans can help control broiler litter moisture levels, leading to healthier flocks and better overall performance.

On March 27, 2018, Dr. Brian Fairchild and Mike Czarick shared the results of recent studies conducted to gauge the effectiveness of circulation fans as part of a webinar presented by WATT Global Media and sponsored by Jones-Hamilton Co. Fairchild, an extension poultry scientist at the University of Georgia, spoke about the importance of litter moisture in flock health. Czarick, senior public service associate at the University of Georgia, spoke about the role circulation fans play in maintaining litter and environmental quality inside the house.

Why litter moisture matters

Inside the poultry house, controlling the litter moisture level is key to controlling a critical factor in bird health: ammonia.

Fairchild explained ammonia levels are elevated when litter is too wet – specifically when litter moisture is between 20 percent and 40 percent. Heightened ammonia levels lead to health and animal welfare issues like footpad lesions, breast blisters, respiratory health issues and leg deformities. Excessively moist litter can also contribute to coccidiosis problems in flocks.

He presented studies showing how paw quality – one indicator of health and welfare – degrades as litter moisture increases over time. Additional research showed that ammonia levels – as well as carbon dioxide – increase as relative humidity rises. Therefore, he said, in order to maintain the best possible bird health, poultry farmers need to set their ventilation rate in order to control litter moisture.

“When it comes to controlling house moisture, the drier you want your litter to be, the lower your target relative humidity needs to be. At 70 percent relative humidity is going to lead to wet litter and 40 percent relative humidity is going to lead to drier litter,” Fairchild said. “Drier litter is going to give us a much better environment for those birds overall in terms of paw quality, air quality and just overall health.”

If moisture is not properly managed, Fairchild said, farmers risk issues like: reduced litter quality; reduced litter treatment life; uneven water lines; reduced paw quality; breast blisters; reduced growth; poor feed conversion and increased disease susceptibility.

Can higher capacity ventilation help control moisture?

Because of this, the objective of ventilation is now to keep the litter very dry under relatively humid conditions, Czarick said. This is going to require greater air movement than traditional circulation fan systems which worked to mix the air from floor to ceiling in order to create a uniform temperature and minimize energy usage. It is possible to maintain dry litter in a relatively damp environment if there’s enough of the damp air moving over the litter.

To meet this challenge, Czarick asked if it’s possible to keep the litter drier not by running the fans more – and using more energy – but by increasing circulation fan capacity. Traditionally, circulation fans are mixing about 10 percent of the air in the house every minute. He wanted to know what would happen if that capacity was increased to 20 percent or even higher.

Testing elevated circulation capacity

Czarick discussed a pair of studies examining this concept. One study compared the performance of three total houses: two with fans capable of mixing about 9 percent of the air – using 18 inch, one-tenth horsepower circulation fans – and one house with fans capable of mixing about 18 percent of the air – using 24 inch, one-third horsepower circulation fans. One house with 18 inch fans maintained about 50 percent relative humidity, while the other maintained between 60 to 70 percent relatively humidity. The house using the larger fans maintained about 50 percent relative humidity. Connie Mou, a poultry science graduate student at the University of Georgia, assisted in facilitating the experiment as well as data collection and analysis. The study was sponsored by the US Poultry & Egg Association.

In the study, footpad lesions were monitored as a way to track the fans’ effectiveness at controlling moisture at the litter level. The results showed the house with the higher capacity ventilation recorded the lowest amount of footpad lesions whereas the house with the lower circulating fan capacity and highest humidity recorded the most lesions of the highest severity.

“When we provided a fair amount of air movement with those higher capacity circulation fans, we dramatically improved paw quality and we significantly improved litter moisture,” Czarick said.

Promising results

A subsequent study, which studied the extremes – comparing one house with no circulation fans and one with high volume circulation fans – backed up the results of the first experiment. Mou was also involved in this trial. Moreover, the house with the circulation fans showed more uniform litter moisture and lower overall moisture levels than the house with no fans. The study did not monitor ammonia levels in the house.

Czarick also observed the birds were also less likely to pile up in certain areas and more likely to spread out in the house with the circulation fans compared to the house without fans.

“What it looks like now is with our newer houses that we can be more aggressive with the amount of air movement that we have in our houses, and because we are moving the air around we’re able to keep drier litter, be able to generate less ammonia and the birds health is improved,” Czarick said.

Cost implications of switching to higher capacity fans

Making improvements like those outlined in the research will cost significantly more than the conventional circulation fan set-up, Czarick said in response to an audience question.

“What we’re looking at in the future is the use of the sub-$100 fans to mix the air, when it comes to (antibiotic-free) when we’re really interested in keeping the litter dry, I think those days are numbered,” Czarick said. “I think we’re going to have to be looking at fans that cost a lot more.”

While there’s a range of factors effecting the cost of the transition – including house design and roof height – he estimated the price of providing adequate circulation fan capacity could be doubled if not tripled. However, he said the bigger, high capacity fans – the models used in his experiments cost more than $200 each –  are built to last for 15 years. Comparatively, the models used in most houses right now only last for two or three years. Replacing cheaper, lower capacity fans with more expensive, higher capacity models will cost a lot up front, but the cost should be comparable during the life of the new fans thanks to their superior quality.

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