The production of chickens has shifted from free-range farming to confined indoor factory production since the 1930s. Modern broiler houses hold tens of thousands of chickens and control lighting, temperature, and automated feeding to maximize growth. A major issue is the accumulation of ammonia-rich chicken manure on the floors, which can harm chickens' health. Litter materials like wood shavings are used to absorb moisture and slow ammonia production from uric acid in droppings, but ammonia levels still often exceed thresholds that impact chickens. Chemical litter treatments were developed in the 1990s to temporarily reduce ammonia, though their effectiveness depends on various management factors, and there is no single best treatment.

1. Poultry and Ammonia
Raising chickens for eggs and meat changed from free-range farming to factory production
methods gradually from the 1930's to the 1970's. It was discovered that chickens would lay more
eggs and get fatter faster if you confined them indoors and kept the lights on at night. By 1965
one person could operate a plant producing forty thousand birds a day.
A modern broiler house is usually 20,000 square feet, but houses as large as 32.000 square feet
are not unusual. They are climate controlled, and can be cooled in the summer and heated in the
winter. Access to a special diet of high protein feed is delivered via an automated feeding
system. This is combined with artificial lighting conditions to stimulate growth. The desired
body weight is achieved in 4 - 8 weeks, depending on the approximate body weight required by
the processing plant.
A major issue with modern broiler houses continues to be the floor where chicken manure
accumulates. The air can become highly polluted with ammonia from the droppings. This can
damage the chickens' eyes and respiratory systems and can cause painful burns on their legs
(called hock burns) and feet.
The floors of modern broiler houses are typically covered with high carbon materials such as
wood shavings or rice hulls prior to birds being introduced to the house. This material along with
the bird droppings that accumulate there are known as litter. The wood shavings add their natural
carbon to the droppings, accelerating decomposition. It lessens the birds contact with their
droppings, helps to absorb excess moisture, and the decomposition process helps to somewhat
mitigate disease and ammonia.
Poultry litter contains uric acid. When exposed to moisture, air and microbiological degradation,
the uric acid is converted to volatile ammonia that increases pH in poultry litter (near pH 8.5). As
poultry litter dries, the pH becomes more neutral (near pH 7). The highest concentration of
ammonia in a poultry house is experienced within a few inches above the litter surface where
chicks are susceptible to its detrimental effects on eyes and lungs. Coupled with elevated relative
humidity levels in houses and the high moisture contents of litter in houses cleaned after a
previous flock, ammonia can have a devastating effect on the health of chicks. Most poultry
losses occur soon after chicks are introduced to the houses because of respiratory tract damages
or illnesses, such as pneumonia, that may result in death.
The detrimental effects of ammonia in poultry production have been known for years. Numerous
laboratory and field studies have shown how ammonia levels as low as 10 parts per million
(ppm) affect bird health and performance. Ammonia levels above 25 ppm in the poultry house
can damage the bird's respiratory system and allow infectious agents to become established,
leading to declining flock health and performance. E. coli bacteria can be significantly
increased in the lungs, air sacs, and livers of birds exposed to ammonia because of damage
that occurs to the tracheal cilia. Resistance to respiratory disease may be decreased. In addition,

2. body weight, feed-efficiency, and condemnation rate may be higher in birds exposed to levels of
ammonia exceeding 10 ppm.
The volatilization of ammonia has been attributed to microbial decomposition of nitrogenous
compounds, principally uric acid, in poultry house litter. Litter pH plays an important role in
ammonia volatilization. Once formed, the free ammonia will be in one of two forms: as the
uncharged form of NH(3) (ammonia) or the ammonium ion (NH(4)), depending on the pH of the
litter. Ammonia concentration tends to increase with increasing pH. Ammonia release remains
low when litter pH is below 7, but can be substantial when litter pH is above 8. Uric acid
decomposition is most favored under alkaline (pH>7) conditions. Uricase, the enzyme that
catalyzes uric acid breakdown, has maximum activity at a pH of 9. As a result, uric acid
breakdown decreases linearly for more acid or alkaline pH values. One principal ureolytic
bacterium, Bacillus pasteurii, cannot grow at neutral pH, but thrives in litter above pH 8.5.
Typically, litter pH in a broiler house ranges between 9 and 10.
To reduce the potential effect of ammonia on chick health when re-using poultry litter, poultry
producers have depended on chemical litter treatments that reduce the ammonia loss from litter
when chicks are most vulnerable to high ammonia concentrations. Poultry litter treatments
acidify litter, a condition under which ammonia is not volatile, and chemically bind some
ammonia. This condition, however, is short-lived but can reduce losses of chicks in early growth
stages.
The first products marketed to control ammonia in poultry houses began appearing in the early
1990's. They were highly acidic chemicals designed to hold down ammonia temporarily. Prior to
their introduction, farmers usually cleaned out all their litter after every flock. The effort required
to do a full cleanout, along with the cost of shavings or other litter materials made solutions that
would allow multiple flocks to use the same litter seem attractive.
One primary question for those involved in poultry production is "What is the best litter
treatment?" Unfortunately, this most frequently asked question has no general answer, and the
difficulties in addressing this question may be complicated and numerous. There has never been
an experimental study evaluating the various litter treatment products under various management
conditions. Litter moisture, brooding and lighting programs, ambient temperature, strain type,
ventilation management, litter management, and disease challenge are only a few of the variables
that have a potential impact on product selection, efficacy, and potential return on investment.
In the selection of a litter treatment product, one must identify the goals for application. Litter
treatments may be cost-effective and justifiable under one or more of the following situations:
 high fuel prices
 extremely cold weather
 short layout periods
 persistent disease challenges
 severe vaccination reactions
 reduction of ammonia-related stress
 prolonged litter reuse

3.  increased bird density
 address marginal management or housing situations
In general, the control of house ammonia levels is the primary purpose for using a litter
treatment. In recent years, the reasons for using a litter treatment and any potential benefits from
its use have expanded to include improvements in performance, environmental concerns, and
disease control. Some litter treatments may be used to enhance the composition of the litter as a
fertilizer or as part of a best management practice to reduce food borne pathogens. Ammonia-
reducing litter treatments offer a potentially better in-house environment for both birds and
producers. They may also play a role in reducing ammonia and odor emissions from poultry
facilities thereby making them better neighbors. Although different litter treatments vary in their
ability to control ammonia, each offers a unique set of characteristics that need to be considered
in selecting the appropriate product to meet an individual's needs. The litter treatment that offers
the best return on investment will depend on the user's ability to select the product that best
meets application goals.