Managing poultry litter effectively is essential for reducing salmonella.
When litter becomes contaminated, birds can ingest the bacteria, increasing the risk of foodborne illness and potential contamination in processing plants.
Recent research, led by the author of this article, showed that controlling moisture levels and using PLT (sodium bisulfate) are two practical strategies poultry farmers should implement to reduce salmonella survival in litter, leading to healthier flocks and safer poultry products.
Understanding Water Activity, Bacteria Growth
Bacteria and other microbes thrive in wet conditions, as they need water for metabolism.
Water activity (a measurement of the free water in a substance, designated by the unit aw) indicates how much water is available for microbial growth. It’s measured on a scale from zero to 1 where 1 means pure water and lower values indicate less available water for bacteria, like salmonella, to survive.
In this study, researchers tested poultry litter at three water activity levels to represent the dry to wet litter conditions commonly found in poultry houses:
• Dry litter (aw 0.85)
• Moderate moisture litter (aw 0.90)
• Wet litter (aw 0.95)
Relationship of Water Activity, Moisture
Moisture content and water activity are related but not the same thing.
Moisture content is the total amount of water present in the litter, including both free and bound water. Depending on the litter type and composition, moisture content can vary at a fixed water activity level.
This study used windrowed used litter, which was originally pine shavings from commercial broiler farms. The moisture content for each water activity level was estimated:
• aw 0.85 — 25% moisture
• aw 0.90 — 32% moisture
• aw 0.95 — 50% moisture
PLT Application
PLT (sodium bisulfate) is a mineral-based acidifier that lowers litter pH and eliminates ammonia for improved air quality in poultry houses.
This acidifier created an unfavorable acidic environment for bacteria and other pathogens because most microbes can’t survive in acidic conditions.
This study challenged the litter of different water activities with a mix of salmonella, including S. enteritidis, S. typhimurium and S. Heidelberg, which are the most common salmonella serotypes that cause foodborne illnesses associated with poultry products.
Then, the PLT was top-dressed on the litter at three application rates:
• No PLT (control)
• Moderate PLT (100 pounds/1,000 square feet)
• High PLT (150 pounds /1,000 square feet)
Salmonella survival, pH, moisture content and water activity were measured over eight days.
Key Findings
• Drier litter means lower salmonella.
Salmonella survival was significantly lower in dry (aw 0.85) and moderately dry (aw 0.90) litter compared to wet litter (aw 0.95). Even without chemical treatment, dry conditions naturally suppressed bacterial growth.
• Wet litter increases risk.
Salmonella persisted much longer in wet litter, reinforcing the need for poultry houses to maintain dry conditions.
• PLT helps reduce Salmonella.
PLT lowered litter pH from about 8 to a range of 2 to 5, depending on moisture content and application rate. This unfavorable acidic environment helped reduce salmonella faster by making the litter inhospitable for bacteria.
• Best results: dry litter and PLT
The most effective strategy combined low moisture with PLT treatment. When applied to the driest litter (aw 0.85), Salmonella declined at the fastest rate.
However, in wet litter, even PLT could not eliminate bacteria as effectively, suggesting excessive moisture limits its effectiveness.
Practical Steps for Poultry Farmers
• Keep litter dry by ensuring proper ventilation, fixing leaks and adjusting drinkers to prevent excess moisture from accumulating.
• Monitor moisture levels by regularly checking moisture content or water activity to detect problems early before they lead to increased bacterial survival.
• Use PLT wisely. PLT is most effective in dry litter. If litter is wet, higher PLT rates may be needed, but moisture control should always come first.
• Plan for reapplication since PLT lowers pH quickly, but its effect is not permanent. Depending on litter conditions, multiple applications may be required to maintain bacterial suppression.
Why These Findings Matter
Controlling salmonella in poultry litter is critical for maintaining a healthy flock and producing safer poultry products for consumers.
While PLT can be a valuable tool, it should be viewed as a supplement to good moisture management — not a substitute for it.
Wet litter counteracts the benefits of PLT, making it less effective at reducing Salmonella levels.
Farmers who prioritize keeping litter dry and apply PLT strategically can achieve better flock health, reduce contamination risks and enhance overall food safety.
Additionally, managing litter conditions properly can lead to better farm performance by reducing disease risks, improving bird welfare, and minimizing ammonia buildup that affects air quality in poultry houses.
Investing time in moisture monitoring and litter management can lead to significant long-term benefits for both producers and consumers.
Source: Lancaster Farming
