NH3 Guidelines in Poultry Farming

Both concentration and exposure time may
influence the effect that NH3 can have on poultry
and worker health. The National Institute of Occupational
Safety and Health has established a
time-weighted human threshold limit value of 25
ppm for 8 to 10 h of exposure. The Occupational
Safety and Health Administration has an 8-h
exposure level at 50 ppm. The short-term exposure
limit (15 min) set by the American Conference
of Governmental Industrial Hygienists is
35 ppm [12]. The level that is considered an
immediate danger to life and health is 300 ppm.
While these levels refer to concentrations that
might have negative impacts on human health,
similar recommendations for poultry have been
made. Beker et al. [13] found that NH3 in poultry
houses lowers performance and may increase
disease susceptibility. It has been suggested that
686 JAPR: Review Article
NH3 should not exceed 25 ppm in poultry houses
[6]. However, prolonged exposure to concentrations
as low as 20 ppm can be detrimental to bird
health and performance, when poultry remain in
such an environment throughout the production
period [14]. These recommended levels have
been reinforced within a more recent study in
which broilers exhibited lower BW gains when
exposed to NH3 levels of 25 ppm or greater [15].
Broiler feed consumption and feed efficiency
has been shown to decrease during exposure to
levels of NH3, ranging from 25 to 125 ppm [15,
16, 17]. Symptoms of NH3 poisoning in poultry
include snicking, tracheal irritation, air sac inflammation,
conjunctivitis, and dyspnea [6]. Exposure
to 20 ppm for long periods of time has
resulted in a variety of disorders, including increased
Newcastle disease susceptibility and respiratory
tract damage [14]. Levels of 75 to 100
ppm are associated with changes in the respiratory
epithelium, including loss of cilia and increased
number of mucus-secreting cells [18,
19]. Exposure to 25 ppm for 42 d resulted in
decreased feed efficiency [20] and after 56 d
resulted in airsacculitis following infectious bursal
disease exposure [21, 22]. Exposures to 46
to 102 ppm resulted in eye damage in the form
of keratoconjunctivitis [23]. After eye damage
has occurred, birds may experience difficulty in
finding feed and water sources. Bird performance
and health can, therefore, be affected by
both respiratory disease challenge and physical
damage due to increased NH3 concentration.
Concern has been expressed about NH3 in
poultry houses on the basis of animal welfare
[24]. Animal welfare, food marketing, and poultry
industry groups are currently debating
whether to set limits for NH3 exposure and concentration
levels in poultry houses based on welfare
implications. The concentration standards
as yet have not been established, but initial proposals
have ranged from 10 ppm as a goal to
25 ppm as a maximum level [25]. Maintaining
such low concentrations will be a difficult challenge
under current commercial production
practices without the potential of putting excessive
financial burden on poultry producers. Further
reviews ofNH3 as it relates to poultry health,
production, and welfare have been published by
Carlile [6], Kristensen and Wathes [24], and Al
Homidan et al. [26].
AMMONIA EMISSIONS
AND ENVIRONMENTAL EFFECTS
Modern intensive animal feeding operations
and the relatively large quantity of NH3 produced
by the excreta associated with these facilities
has heightened environmental concerns over
NH3 emissions. It has been suggested that nearly
50% of the NH3 emissions from human-related
(anthropogenic) sources come from livestock
operations [27] (most of the rest coming from
inorganic fertilizer). Poultry production has been
estimated to be responsible for 1.9 million metric
tons of ammonia emissions annually. Tables 1
and 2 depict the estimated NH3 emission contributions
of various domestic animal species on
a global [28] and US [29] basis.
Once emitted, NH3 can rapidly react with
acidic compounds found in the atmosphere, such
as nitric acid and sulfuric acid, and be converted
to aerosolized ammonium particles, typically as
ammonium sulfate and ammonium nitrate. As
aerosols, N compounds can impact ecological
balance, biodiversity, and water systems. Deposition
back onto soil, vegetation, or water usually
occurs within a matter of days and thus in relatively
close proximity to the emission source.
Once deposited, N can impact soil acidity, forest
productivity, terrestrial ecosystem biodiversity,
stream acidity, and coastal productivity [30]. Of
particular concern is high atmospheric N contributions
in the formation of acid rain that may
damage plant life, cause excessive fertilization
of soils and vegetation, increase algal blooms
in surface waters, and damage aquatic life. In
general, plant growth globally is limited by N.
Deposition of N, therefore, can cause increased
plant growth [31]. Silvaculture studies in North
America and Europe document accelerated forest
growth in recent years, and a portion of this
faster growth has been attributed to increased
atmospheric N inputs [32, 33]. European forests
that receive N from atmospheric deposition also
show an increase in nitrate leaching, as much
as 30% of inorganic N deposition [34]. Several
studies have shown that in temperate zones fertilizer
inputs and atmospheric N can lead to soil
acidification [35, 36]. Many plant species in unmanaged
ecosystems are adapted to low N environments.
Emissions of N compounds can result
in N fertilization and species change in natural

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