Three keys to controlling pathogens in poultry litter

Litter is a piece of poultry health and performance that often goes overlooked. Controlling the substrate’s heat, humidity and acidity can yield benefits for the animal and the grower.

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Temperature, moisture content and litter pH are key variables in the level of pathogens in the house.
Temperature, moisture content and litter pH are key variables in the level of pathogens in the house.
(Courtesy Big Dutchman)

Litter is a piece of poultry health and performance that often goes overlooked. Controlling the substrate’s heat, humidity and acidity can yield benefits for the animal and the grower. 

As part of the Poultry Federation’s 2021 Poultry Symposium for Production & Processing, Animal Waste Management Consulting Services President Dr. Josh Payne spoke about litter pathogen reduction strategies. The event was held April 14-16, 2021. 


Josh PayneJosh Payne, Animal Waste Management Consulting Services (Todd Johnson)

 


Poultry litter 

Litter is a key building block for raising healthy birds. In a poultry house, litter absorbs moisture from droppings, insulates the cold floor and provides a comfortable surface for the animals. 

Along with a substrate, poultry litter is made up of bacteria, viruses, fungi and insects. It includes varying levels of nutrients like nitrogen, phosphorus and potassium. The level of nitrogen, Payne said, is correlated with ammonia production in the house. 

Removing antibiotics from production can create a shift in litter microflora with higher pathogen loads in the substrate. Using older litter, with more manure packed in, increases nitrogen levels and leads to higher levels of ammonia in the house. Litter is moister due to larger birds and wetter droppings from vegetable-based diets. 

Managing the pathogen load 

Litter quality can impact the performance of subsequent flocks. Growers are managing litter for each flock that will live on it. The time litter is treated and the amount of downtime it is given between flocks impacts birds later in the litter’s life cycle. 

One goal of litter management is controlling the pathogen load. Temperature, moisture content and litter pH are key variables in the level of pathogens in the house. 


Young Broiler Chicken CloseupLitter absorbs moisture from droppings, insulates the birds from the cold floor and provides a comfortable surface for the animals. (Greg Miles | Dreamstime.com)

 


Temperature

Raising the litter temperature can significantly impact pathogen load. Often, it is achieved through windrowing. Pathogens grow best in a litter temperature of about 98° Fahrenheit (36.6° Celsius). When windrowing, the target temperature for the optimal pathogen kill is 131° F (55° C). 

In-house windrowing can achieve those high temperatures if properly conducted. However, that requires careful management by the grower and a longer downtime of at least 14 days in between flocks. Payne did not recommend windrowing during the winter months due to the difficulty of — and possible hesitancy of growers toward — ventilating to remove ammonia from the house.

Windrowing can be challenging because it mixes wet cake with the rest of the litter. Hot core temperatures must be achieved to drive off moisture. Nevertheless, windrowing requires a moisture content greater than 30% to work. Growers must decide if its best for them to remove wet, caked litter by decaking ahead of windrowing. 

Additionally, windrowing requires a high level of carbon for heating to occur. Older, built-up litter may not be able to reach the necessary 25 to 1 carbon to nitrogen ratio. Fresh bedding is likely needed for proper windrowing. 

After heating it up, particles in the litter are degraded to a fine size and the material’s absorbency is lost. When the wet litter is redistributed, it disperses the pathogens into the litter and produces high ammonia levels. Longer downtimes are needed to purge the ammonia from the house. 

Growers must also check the temperature of the windrows by using a long stem thermometer and checking the core of the windrows. The pile must be turned so all of the litter is exposed to the high temperatures at the core of the windrow. 

Moisture

For moisture content, Payne said, the lower the better. Bacteria require water to live and wet litter can lead to ammonia production. Keeping litter drier is ideal. 

Bedding depth: Starting off and keeping the correct bedding depth is critical to success. Typically, about 4 to 6 inches are needed. This insulates the floor, regulates the bird’s body temperature and wicks away moisture. Shallow litter can easily become saturated to the pad and cause issues with pathogen proliferation. 

Humidity: The ideal relative humidity is between 50% and 65%. If the level reaches above 70%, litter starts to slick over. When that happens, ventilation should be adjusted. 

He recommended using a hygrometer to check relative humidity and monitor potential litter wetness. These devices monitor relative humidity at the litter-air interface. Hand held hygrometers work well because they are placed at the bird level and tend to get more accurate readings than controllers.

Directional airflow: Airflow must be established and maintained to bring in cold, moist air and mix it with warm air in the center of the house. This will ensure that the birds feel warm air while preventing chilling the birds and wetting the litter. 

Water line management: Wet areas underneath leaking water lines can be a source of pathogens and ammonia that affect paw quality. Wet litter sticking to paws with ammonia present can lead to footpad burns. 

Downtime: In between flocks, the house must be closed and heat within the litter should be utlilized to reduce moisture and ammonia. Closing the house also enhances biosecurity. Minimum ventilation should be used to enhance removal of ammonia and moisture. 

Litter should be managed within the first 48 hours after a flock departs, and then left to rest for the remainder of the downtime. Whether decaking or windrowing, it is important to do it as soon as possible. Litter should be left undisturbed for at least three days prior to amendment application. The substrate is still actively producing high levels of ammonia. 

Decaking: When decaking, only caked litter should be removed. Decaking should be kept as shallow as possible. The entire house may not need to be decaked. Growers should focus on removing caked litter below the feed and water lines.

Preheating: Thorough heating drives away moisture and ammonia. If a house isn’t properly heated, only the 1/2 to 1 inch of litter will be dried out. This will create health and performance issues in the flock. 

It’s possible to tell if the house hasn’t been preheated by seeing if it can be "balled up." That indicates an excess of moisture and ammonia, and a lack of proper preheating prior to placement. 

pH level

Pathogens prefer a pH of 6-8. Poultry litter is 7.5-8.5. Acidic environments are more likely to be hostile to pathogens, so managing the litter pH to a more acidic state will help reduce pathogenic proliferation.

Litter treatments are typically applied pre-flock for ammonia control. An additional benefit they provide is that they decrease litter pH, creating an anti-pathogenic effect on the surface. 

pH is key to manage, Payne said, during the first week after birds are placed due to their gut’s microflora formation. Payne explained that the right pH manipulation can help birds take up more favorable microbes from the litter, such as Lactobacillus, and avoid pathogens that prefer a higher pH level. Dropping the litter pH level below 4 for the first week can impact what bacteria are colonizing in the chicks' guts. 

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