2004 Poultry Science Association, Inc.
A Review of Literature Concerning
Odors, Ammonia, and Dust from
Broiler Production Facilities: 2. Flock
and House Management Factors
J. B. Carey,*,1 R. E. Lacey,† and S. Mukhtar†
*Department of Poultry Science Texas A&M University, College Station,
Texas 77843-2472; and †Department of Biological and Agricultural Engineering,
Texas A&M University, College Station, Texas 77843-2117
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Primary Audience: Extension Specialists, Poultry Scientists, Poultry Farm Managers
SUMMARY
Confinement buildings are one of the most likely sources of odor in a broiler operation. The
buildings must be ventilated, either mechanically with fans or relying on natural airflow, to prevent
animal mortality and enhance animal health. Consequently, odors generated within the building
are carried to the surrounding environment by the ventilation system. This review addresses the
management of those factors that affect the production and removal of odorants in a broiler
production operation. Published literature does not specifically discuss odor generation within
broiler houses. Several studies deal with ammonia (an odorant gas) or particulate matter (a pollutant
thought to carry odorant gases) emissions in broiler houses. These studies are discussed and
inferences are made about the generation of odors under similar conditions.
Conditions that lead to higher moisture in the litter tend to increase ammonia release, and by
inference, more odorant release. Higher litter moisture is presumed to encourage greater microbial
degradation of uric acid excreted by the birds into the litter and release more ammonia. Evaporative
coolers may produce excess water droplets that fall to the litter rather than evaporate to cool the
incoming air. Broiler houses that use misting systems generally have higher moisture content in
the litter at the inlet end of the house. Either type of evaporative cooling system may also reduce
litter drying rates by increasing humidity levels within the house. At the other extreme, low litter
moisture could lead to the production of more particulate matter (i.e., dust), a pollutant that can
transport odors to the atmosphere. The optimum litter moisture content that can minimize odorant
and dust release is somewhere within the range of 25 to 35%, but exact values for optimum balance
depend on numerous house-specific conditions. Changes in dietary nutrient levels can alter the
production of ammonia by varying the amount of nitrogen available; however, most currently
researched methods show negative impacts on productivity. Management of watering devices is
critical to controlling litter moisture. Proper water equipment maintenance and operation are part
of daily house management strategies to control litter moisture and, therefore, dust and odor.
Key words: broiler production, odor, litter management
2004 J. Appl. Poult. Res. 13:509–513
DESCRIPTION OF PROBLEM which the floor is covered in an absorbent mate-
rial (i.e., litter). Conditions within these confine-
Production of broiler chickens in the US is ment buildings are managed to optimize bird
primarily done within enclosed structures in health and productivity. Factors that affect the
1
To whom correspondence should be addressed: j-carey@tamu.edu.
510 JAPR: Review Article
interior conditions include seasonal climate and monia emissions. Those factors related to poul-
weather conditions; building ventilation, heating try house and flock management include dietary
and cooling; and factors that affect the litter manipulation, adequate bedding, exhaust air
(e.g., feed spillage, flock husbandry, litter man- cleaning, and use of ventilation systems to dry
agement). These factors are interrelated in estab- litter.
lishing the composition of the interior air in the
building. Because commercial broiler produc- LITTER MANAGEMENT
tion is totally confined, the air in the building Management of broiler litter to reduce am-
contains all of the materials emitted to the atmo- monia volatilization is largely a matter of con-
sphere; some of which are potential pollutants trolling litter moisture and pH. Control of litter
(e.g., ammonia, dust, and odorants). pH over the life of the flock has proven to be a
difficult task. Reece et al. [4] demonstrated that
HOUSE AND SITE FACTORS
litter ammonia release was negligible at litter
The American Society of Agricultural Engi- pH below 7. Ammonia release began when pH
neers [1] has suggested separation distances for was near 7 and reached a maximum at pH 8 and
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site selection of animal production facilities above. These researchers examined treating the
from residential developments (1 mi) and indi- litter with monobasic calcium phosphate at 0.4
vidual rural residences (0.25 to 0.5 mi). Many and 1.0 kg/m2 or phosphoric acid at 0.4 kg/m2
states have regulatory requirements that estab- in an attempt to adjust litter pH during grow-
lish minimum set-back distances for broiler pro- out, but no treatment was effective after 17 d.
duction facilities. Regulatory constraints Ellicott and Collins [5] modeled ammonia re-
notwithstanding, it is best to locate broiler pro- lease from broiler houses and found litter pH,
duction facilities such that impact on sur- temperature, and moisture content (in that order)
rounding property is minimized. Local airflow to impact ammonia release. Carr et al. [6] found
and human traffic patterns may necessitate dis- that ammonia concentration increased with in-
tances in excess of those stated above to prevent creases in litter pH, temperature, and moisture
negative impact. level. They stated that increased ventilation
In a study of broiler and pig slurry in The caused a decrease in ammonia concentration and
Netherlands, Misselbrook et al. [2] used a series that litter moisture level should be below 35%
of mathematical models to demonstrate that to reduce ammonia concentration in the build-
broiler house odors were more intense than the ing air.
pig slurry, but broiler house odors had a greater Amon et al. [7] studied litter treatment with
slope of intensity on concentration (1.61 for a commercial yucca extract (De-Oderase) and a
swine compared with 2.35 for broilers) and zeolite (clinoptilolite) fed at 2% of the diet and
would, therefore, be easier to abate. A greater spread on the litter at 1.6 kg/m2 in concrete and
slope of intensity means that smaller reductions brick broiler houses in Slovenia. The treatments
in concentration yield greater reductions in had no positive impact on odor, and clinoptilolite
odors. The models thus developed for the rela- actually increased ammonia release.
tionships between odor concentration and odor
FLOCK HUSBANDRY
intensity could be useful in determining the re-
quired abatement strategy to render the odor Flock husbandry encompasses a variety of
acceptable. The effectiveness of any control factors that impact odor and dust. Litter depth
measures, when used in conjunction with such can be a factor as Al Homidan et al. [8] observed
models, could establish minimum acceptable that litter ammonia levels were higher in treat-
distances between the source of an odor and ments with less bedding material. Dietary factors
potential complainants. are discussed more fully in a subsequent section.
Due to regulatory constraints, ammonia Ferguson et al. [9] examined the impacts of di-
emissions are of utmost importance in the UK. etary CP levels on litter ammonia and found that
Phillips et al. [3] used a ranking system to eluci- their dietary treatments had no significant impact
date approaches to livestock management and on litter ammonia. They did, however, confirm
waste storage that had feasibility to reduce am- the relationship between higher litter moisture
CAREY ET AL.: REVIEW: FLOCK AND HOUSE MANAGEMENT 511
and increased litter ammonia. Increases in litter dium group and also between the medium and
moisture from approximately 56 to 60% resulted low treatment group.
in an increase in litter ammonia release. The Si et al. [15, 16, 17] studied the impacts of
positive impacts of litter management can also lowering CP levels accompanied by supplemen-
improve broiler health. McGovern et al. [10] tal synthetic amino acids in an attempt to reduce
demonstrated that oiling broiler litter with feed- nitrogen excretion while maintaining growth and
grade canola oil reduced dust levels by up to feed efficiency in broilers. Reducing CP below
32%. Willis et al. [11] used evaporative cooling 20%, while providing indispensable amino
systems to control broiler house dust. Treated acids, consistently resulted in reductions in BW
pens had higher ammonia and moisture but and feed conversion of the broilers. Extensive
lower dust. Broiler BW of the treated pens work to elucidate specific amino acids that may
were higher. contribute to the poor performance has failed to
determine the necessary amino acids required
Dietary Influences to restore growth and feed efficiency in lower
protein diets. Chavez et al. [18] reported signifi-
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Terada et al. [12] studied the impact of feed-
cant differences among methionine sources on
ing lactosucrose in broiler diets on cecal mi-
the odor volatility of broiler excreta. This could
crobes and odor compounds in cecal contents.
provide additional management strategies to re-
These researchers reported significant reduc-
duce or alter odors from broiler production
tions in cecal ammonia, phenol, and cresol
facilities.
among birds fed lactosucrose. They also reported
Litter dry matter content and nitrogen losses
increases in cecal acetic acid and butyric acid
were lower when using nipple drinkers vs. bell
among birds fed lactosucrose. Pen ammonia lev-
drinkers [13]. Presumably conditions favoring
els were significantly lower in the lactosucrose-
reduced nitrogen loss would also favor reduced
fed birds, and the researchers observed that pen
odor production. However, if the litter is too dry,
odor was reduced in the lactosucrose-treated
then increased dust concentrations may occur in
groups.
the building.
Elwinger and Svensson [13] examined the
impact of protein level on ammonia emission
Water Systems
and litter nitrogen in broilers in Sweden. Based
on nitrogen balance estimates, they calculated Guidelines for drinker management in rela-
that the loss of nitrogen attributable to ammonia tion to season of the year are provided by manu-
losses increased as dietary protein level in- facturers [19]. Birds drink substantially less
creased but numerous measurements of litter water in cooler weather; thus, it is necessary to
ammonia did not detect any differences in am- reduce pressure in drinker systems during cooler
monia volatilization from the litter. weather to prevent wet litter conditions that can
An initial experiment by Ferguson et al. [9], lead to increased ammonia release and related
examining the impact of low CP on broiler problems. Each manufacturer has recommenda-
growth and litter composition, found no impact tions regarding drinker pressure for birds of all
on litter ammonia levels but did report signifi- ages and under all environmental conditions.
cant reductions in litter nitrogen levels. In other Additional difficulties occur when house floors
work, Ferguson et al. [14] compared low, me- are not level. Some form of pressure equalizer
dium, and high CP levels in broiler diets. The or additional regulator is needed in the system
low and medium treatments were supplemented to assure proper water pressure throughout the
with synthetic amino acids. Litter ammonia lev- length of the system. General recommendations
els tended to be lower for the low and medium for finding the proper water pressure involve
CP treatments compared with the high treatment. careful observation of litter conditions sur-
Litter pH of the low treatment was significantly rounding the drinker system. If the litter is wet,
reduced compared with the high treatment the pressure needs to be reduced or the drinker
group. Litter moisture and total nitrogen was height needs to be raised. Litter age, season of
significantly reduced between the high and me- the year, bird age, and equipment condition all
512 JAPR: Review Article
play a role in determining the proper drinker problems are the single biggest threat to a com-
pressure. posting operation. They recommend that com-
posting facilities be placed a long distance from
COMPOSTING OF LITTER
neighbors and property lines. The 3 primary
AND MORTALITY sources of odor are raw materials, ammonia, and
Wet litter and dead birds are among the po- anaerobic conditions within the compost stack
tential sources of odor at a broiler operation. or row. Anaerobic conditions can be eliminated
Processing of litter and mortalities by compost- through assurance of proper moisture and aera-
ing helps reduce odors and volumes of waste tion. Ammonia odors can be controlled by pro-
generated. On the other hand, a poorly managed viding extra carbon sources (such as straw or
composting operation will add one more source wood shavings) to the mixture. Strong-smelling
of odor.
raw materials can be eliminated through timely
Managing a major die-off requires extra at-
and effective collection and use. Reduction of
tention to the factors that could result in the
odors from strong smelling raw materials will
development of odors. Carcass burial must be
not occur until the composting process is well
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completed within the 72 h required by regula-
tions, but it is highly advisable that burial occurs underway. Odors can be reduced by increasing
within 24 h. Due to the large number of carcasses the porosity of the mixture and by covering the
associated with a major die-off event, the poten- compost pile with a layer of peat moss or fully
tial for rapid development of strong odors is of composted material. Compost turning, loading,
primary concern. and transportation tend to increase odors. Con-
Natural Resource, Agriculture, and Engi- trol of moisture in raw materials can also reduce
neering Service [20] states that odor control odor problems related to excessive moisture.
CONCLUSIONS AND APPLICATIONS
1. Proper location of poultry facilities is a key factor in the avoidance of odor-related problems.
Other site factors include the potential windbreak walls, tree lines, or fan elbows to improve
air mixing.
2. Litter moisture management is key to odor control. This includes ventilation and drinker man-
agement.
3. Research has demonstrated that litter ammonia release is negligible at litter pH below 7.
4. Consideration of nutritional factors that influence odor production may be warranted if such
changes do not negatively impact bird performance.
5. Management of on-farm mortalities is an important factor in odor management.
REFERENCES AND NOTES
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through amino acid supplementation. 1. Extent to which crude protein
may be reduced in corn-soybean meal diets through amino acid This review was in part supported by contract #582-0-81252 with
supplementation. Abstr. 2000 Int. Poult. Sci. Symp., Atlanta, GA. the Texas Natural Resources Conservation Commission (Study of
Abstr. 50. Odors and Arsenic Emissions from Poultry Growing Operations).
