Ammonia affects performance and thermoregulation of male broiler chickens
Ammonia affects performance and thermoregulation of male broiler chickens1
Shlomo YAHAV 0
0 Institute of Animal Science, Agricultural Research Organization, The Volcani Center , PO Box 6, Bet Dagan 50250 , Israel
- The effects of various atmospheric ammonia concentrations (X ± S.E.; 16 ± 2; 28 ± 3; 39 ± 4; and 54 ± 5 ppm) at high ambient temperature (Ta = 32 °C) and relative humidity (rh = 6065%) on the performance and thermoregulation of male broiler chickens were studied. Body weight declined significantly and proportionally with increasing ammonia concentration in the air. The decline in body weight coincided with a similar pattern in feed intake. Feed efficiency did not differ significantly among treatments, but the broilers exposed to the lowest concentration of ammonia showed the highest feed efficiency. Chickens exposed to the lowest ammonia concentrations regulated Tb at significantly lower levels (41.5 °C at 16 ppm and 41.9 °C at 28 ppm) than those at the highest concentrations (42.3 °C at 39 and 54 ppm). Arterial pH increased with increasing ammonia concentration and was similar in the upper 2 concentrations of ammonia. A similar but opposite trend was found in the partial pressure of arterial CO2. Plasma triiodothyronine (T3) concentration did not differ significantly among treatments. It can be concluded that exposure to increased ammonia concentrations impairs broiler performance. It may also be suggested that ammonia can affect the ability of the chickens to control Tb effectively.
L’ammoniac pourrait également affecter la capacité des poulets à contrôler efficacement leur
ammoniac / poulet de chair / performance / température corporelle / triiodothyronine
The environment maintained in broiler
houses has a major effect on the health and
performance of broiler chickens. Ammonia
gas, one of the poultry house products that
are detrimental to broilers, is produced from
uric acid and undigested proteins in manure,
by aerobic or anaerobic bacteria [
degradation of uric acid and undigested
proteins into ammonia is influenced mainly
by temperature, pH and the manure
moisture content .
The deleterious effects of ammonia on
weight gain, feed intake and feed
conversion of broiler chickens have been reviewed
by Carlile [
], Whyte [
] and Kristensen
and Wathes [
]. However, chronic
exposure to ammonia or previous experience
with it may elicit a compensatory response
to the pollutant and reduce its deleterious
Exposure to ammonia has been found to
cause changes in the pulmonary
ultrastructure that supports the mechanical defense
mechanism of the respiratory system [
and the respiratory system, especially the
dead space, which plays a major role in the
ability to control body temperature at high
ambient temperatures, by panting [
effect of ammonia on the ability of broiler
chickens to thermoregulate is not known.
The objectives of the present study were
to determine the effects of acclimation to
various concentrations of ammonia on the
performance of male broiler chickens and
on their ability to control body temperature.
2. MATERIALS AND METHODS
2.1. Experimental procedure
The study was conducted on
fast-growing male Cobb chickens. All birds were
obtained from a commercial hatchery and
raised for 4 weeks in battery brooders under
regular conditions [
]. At the age of 4 weeks,
192 chickens were selected by weight from
a group of 240 birds. Birds with extreme
weights were discarded. The birds were
divided into 4 treatment groups, each
including 8 replicates of 6 birds, with equal average
body weights in all treatments and replicates.
The birds were housed in cages – 2 birds per
cage – situated in 4 computer-controlled
environmental chambers which maintained
a constant temperature within ±1.0 °C and
relative humidity (rh) within ±2.5%, under
continuous fluorescent illumination.
During the acclimation period (5th week), Ta,
and rh were raised by equal increments to
attain the target environmental conditions
of the experiments: 32 °C and 60% rh (the
optimal rh for raising broiler chickens at
high Ta [
]). The ammonia concentrations
in the chambers were maintained at 16 ± 2,
28 ± 3, 39 ± 4 and 54 ± 5 ppm, respectively,
being controlled by the fresh air supply. The
lower fresh air admission into the chambers
allows maintaining the oxygen available
for the chickens (taking into account the
high volume of the chamber in comparison
to that of the cages). Twice a day, the gas
concentration was measured in different
sites of the chamber with an Ammonia
Electrolyte Sensor (Bionic Instrument, model
TX2460FN-P with GS-2460DP). The diet was
designed according to the National Research
] recommendations, and water
and feed in mash form were supplied
At weekly intervals, body weights and
feed intake were recorded on individual and
group bases, respectively between 4 and
7 weeks of age. Body temperature was
measured with a digital thermometer (Sika
TT-7170) in 10 birds of each treatment group.
At 7 weeks of age, whole blood samples
Within rows, values designated by different letters differ significantly (P ≤ 0.05); n = 8 replicates of
6 birds; BW: body weight; FE: feed efficiency.
were taken from the brachial vein, and were
centrifuged at 1814 g for 10 min to obtain
plasma, which was stored at –20 °C. Arterial
blood samples (2 mL) were drawn from the
brachial artery under anaerobic conditions,
for immediate blood gas and pH analyses.
2.2. Blood and plasma analysis
pH and pCO2 were measured in arterial
blood samples, with a Blood Micro System
(Radiometer, Model BMS3 MK2).
Radioimmunoassay for triiodothyronine (T3) was
performed in plasma samples, with
commercial kits (Coat-A-Count, Canine, T3 kits
- Diagnostic Products Corporation (DPC),
Los Angeles, CA 90045-5597), validated
for domestic fowl [
]. The T3 assay was
characterized by intra-assay and inter-assay
variation (cv) of 7.0 and 9.4%, respectively.
2.3. Statistical analysis
In the experiment, there were 4
treatments (chambers) with different levels of
ammonia. Each chamber contained 8
replicates of 6 birds. The results were averaged
for each group of 6 birds (3 cages) and then
subjected to analyses of variance (ANOVA)
according to Snedecor and Cochran [
and the Duncan multiple range test [
applied to them. The means were
considered significantly different at P < 0.05.
3. RESULTS AND DISCUSSION
The effects of the different concentrations
of ammonia in the air, on the performance
of the male broiler chickens are
summarized in Table I. The initial body weights (at
4 weeks of age) were similar in all
treatments. Body weight declined significantly
with increasing concentration of ammonia.
At 7 weeks of age the decline in body
weight paralleled a similar trend in feed
intake. Feed efficiency did not differ among
treatments, but the highest value was
reached in broilers exposed to the lowest
concentration of ammonia. The results in
this study demonstrate a significant
deleterious effect of aerial ammonia
concentration on body weight gain and feed intake of
broiler chickens, despite 3 weeks of chronic
exposure to the pollutant. Other factors than
ammonia (dust for instance) were unlikely
to be involved in this deleterious effect
because the air entering the chambers was
filtrated, its velocity was very low (0.25 m
per second) and the chickens were housed
In rows, values designated by different letters differ significantly; n = 10 for Tb and 8 for blood analysis.
in cages. These results may, therefore, show
that chronic exposure to ammonia does not
elicit a complete compensatory response
which would eliminate the deleterious effect
on performance, as suggested by Reece
et al. [
] and Johnson et al. [
reducing the ammonia concentration in the
air, may lead to recovery of the chickens
and may therefore evoke some growth
Body temperature was significantly
affected by the concentration of ammonia
in the air (Tab. II). The chickens exposed to
the lowest ammonia concentrations
regulated Tb at significantly lower values than
those exposed to the highest
concentrations. Arterial pH increased with increasing
ammonia concentration and was similar in
the birds exposed to the 2 highest
concentrations. An opposite trend was observed in
the partial pressure of arterial CO2 (Tab. II).
These results suggest a higher panting rate
in broilers exposed to the higher
concentrations of the pollutant [
], but with
lower efficacy to control Tb. Under the low
ammonia concentrations, the broilers
maintained Tb within the known normothermic
range for domestic fowl , whereas
exposure to 39 ppm of ammonia or more
caused significant increases in Tb, which
reached values typical of mild
hyperthermia. In the present study, the air flow speed
was 0.25 m per second, precluding the
possibility of losing heat by convection, and
leaving panting as the main pathway for
heat dissipation. It may be suggested,
therefore, that changes in the pulmonary
ultrastructure, resulting from the high aerial
ammonia concentrations, could affect the
efficiency of panting and hence the ability
to control Tb effectively under these
Plasma T3 concentration did not differ
significantly among treatments, but it was
on average numerically the lowest in
chickens exposed to the lowest ammonia
concentration and higher with an increasing aerial
ammonia concentration (Tab. II). Plasma
T3 is the main metabolic hormone, and
changes in its concentration have been
found to be related to ambient temperature
] and to feed intake in domestic fowls [
16, 17, 18
]. It can be speculated that a
reduced T3 concentration in broilers exposed
to the lowest aerial ammonia concentration
might be associated with the relatively low
energy demands imposed when the chickens
are able to control Tb efficiently. However,
this hypothesis requires further confirmation.
It can be concluded that exposure to
different atmospheric ammonia
concentrations significantly impairs performance, to
an extent which was found to be correlated
with the pollutant concentration. It may also
be suggested that ammonia can affect the
ability to control Tb effectively. For the practical
point of view, it can be concluded that even
under low aerial ammonia concentrations
a significant effect on performance may
appear, therefore, a proper ventilation of the
poultry house is needed.
This study was supported by grant No.
3560360 from the Chief Scientist’s Office of the
Israeli Ministry of Agriculture and Rural
Development, and by the Egg and Poultry Board of
Israel grant No. 356-0350. The author wishes to
thank Mr. M. Rusal and Dr. D. Shinder for
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