Increased litter moisture content increases ammonia volatility in a built-up litter program—and in a big way—making moisture control a vital part of avoiding wet floors, cake and ammonia in poultry houses. While heat also plays a significant role in ammonia volatility from built-up litter—with higher temperatures purging more ammonia from the litter—producers have little flexibility in setting house temperatures since producers must reach target surface temperatures prior to placement. Moisture is the number one variable producers have to manage to help control ammonia production, thereby boosting bird health and performance.
Small moisture increase, big impact
Even slight increases in moisture can translate to a significant boost in ammonia production. Ideally, litter moisture should be between 20 and 35 percent. Research by Miles et al showed that even slight increases in litter moisture can cause substantial increases in ammonia volatility—and that impact is magnified as temperatures rise (Figure 1).1
Maximum ammonia volatilization occurs at approximately 42% litter moisture with temperatures of 75°F; at 95°F, maximum generation occurs near 46% litter moisture. At 95°F and 20% litter moisture content, ammonia volatility is nearly doubled compared to the same moisture content at 75°F.
Production Challenges of Increased Litter Moisture
Excessive moisture will cause litter to cake, which means the litter has been sealed off to create a continually damp, sticky and slippery surface. While this is most commonly seen around drinker lines, sidewalls and corners, severe moisture control problems can cause large areas of a house to cake over. Once litter reaches this state, the litter is saturated with water and it cannot escape. To prevent litter from caking, moisture must be removed through adequate ventilation and proper heating.
Wet litter does not retain heat well, so it can lower bird’s body temperature which can be detrimental to weight gain, feed conversion, paw condition and immune function. Also, since floor temperatures are more important to bird health than air temperatures, increased pre-heating times are necessary to not only prepare wet and dry litter but to maintain bird temperature, which increases fuel costs.
Wet litter also greatly increases pathogen load, and with it the chances of a disease outbreak, as well as incidence of breast blisters, footpad dermatitis, condemnations and downgrades. If caked litter is not removed and moisture is not managed, paw lesions can begin to form in the first week of a bird’s life as the liquid ammonia at the litter surface begins to erode the paw.2
Managing Litter Moisture
Proper broiler litter management is attained when more moisture is removed than deposited where the air and litter meet. To make that happen:
- Preheat houses 48-96 hours prior to bird placement to dry the bedding, purge ammonia and warm the floor.
- Ventilate to maintain the ideal relative humidity of 50-70% during brooding to prevent moisture build-up and increased ammonia production, thereby preventing paw lesions and cake formation.
- Keep litter depth at about 4-6 inches to provide sufficient moisture absorbing and wicking capacity without being too deep. Litter less than five inches deep often has excessive caking. Broilers raised on litter 3 to 5 inches deep consistently demonstrate fewer and less severe paw lesions due to litter moisture decreasing with an increase in litter depth from 1 to 5 inches3. Caked litter must be removed between flocks and replaced with new litter.
- Add an extra inch or two of litter along sidewalls in houses with concrete footers for better insulation. The extra litter will absorb the excess moisture in these high challenge areas.
- Keep litter level throughout the house so it doesn’t interfere with proper drinker and feeder line height.
- Acidify the litter surface with safe acids to neutralize ammonia. Litter pH affects ammonia release and must be below 7 to reduce volatilization. Untreated litter will have a pH near 8 or higher4.
In one , birds raised in houses treated with PLT®-poultry litter treatment to neutralize the ammonia at the litter surface had 19% fewer major paw lesions and 20% fewer minor paw lesions than control birds. Birds raised on PLT also showed a three-point improvement in feed conversion (1.77 vs. 1.80) and a one-point improvement in weight.
As companies grow chickens for longer periods, the houses become more crowded making it difficult to get sufficient air flow across the litter to keep it dry. Litter moisture and its overall condition must be carefully managed starting before the first bird is placed to help ensure drier litter and therefore less ammonia for the incoming flock.
1Miles, D. M., D. E. Rowe, and T. C. Cathcart. 2011. High litter moisture content suppresses litter ammonia volatilization. Poultry Science 90:1 397-1 405.
2Litter Quality and Broiler Performance, Casey W. Ritz, Brian D. Fairchild, and Michael P. Lacy Extension Poultry Scientists, UGA Extension Bulletin 1267, 2014
3The Relationship between Litter Moisture and Foot Pad Dermatitis, Brian Fairchild, UGA Extension Bulletin 2010
4Wheeler, E. F., K.D. Casey, R.S. Gates, and H. Xin. 2008. Ammonia emissions from USA broiler barns managed with new, built-up, or acid-treated litter. Proceedings of the Eighth International Livestock Environment Symposium. Iguassu Falls City, Brazil. ASABE. St. Joseph, MI. 10 pp.