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Infectious Bronchitis Virus (IBV) And Vaccination
Of Broilers
Vaccination protects broilers from IBV despite
exposure to moderate ammonia levels
Properly vaccinated commercial
broilers are protected from an infectious bronchitis virus (IBV) challenge
despite exposure to moderate ammonia levels, according to a study that
surprised researchers.
Ammonia remains a persistent problem
for the broiler industry because higher
levels coincide with an increase in airsacculitis and condemnations,
especially in winter when ventilation tends to be less
than ideal, Emily Aston, DVM, of the University of Georgia, told Poultry Health Today.
Aston and colleagues sought to
determine the impact of ammonia on the immune response to IBV vaccination.
For their study, they administered an IBV Massachusetts-type vaccine
to 1-day-old chicks.
They placed the
chicks in a climate-controlled room and exposed them
to 30 to 60 parts per million of ammonia.
Other birds in the study were not
vaccinated and exposed to the same levels of ammonia, and some birds were
vaccinated but were not exposed to ammonia.
At 28 days of age, birds in
the study were challenged with IBV M41, a strain of the virus similar to
the vaccine.
‘Completely protected’
“IBV-vaccinated birds in both
ammonia and no-ammonia groups were completely protected from challenge and
showed significantly reduced viral load, clinical signs, no
ciliostasis and no airsacculitis,” Aston reported at the International Poultry
Scientific Forum.
Among the unvaccinated, challenged birds, 90% exposed
to ammonia had airsacculitis compared to 40% to 50% of those that
weren’t exposed to ammonia.
The results surprised the
investigators because past research indicates that ammonia exposure would
negatively affect the immune response to IBV vaccination and
protection against challenge, Aston said.
Aston noted
that although ammonia’s contribution to poor air
quality remains one of the biggest issues confronting the poultry
industry, other factors are involved such as humidity levels,
temperature, dust and carbon dioxide.
Still unknown is whether exposure
to higher ammonia levels, coupled with factors such as
insufficient vaccination and environmental stressors, can increase the
risk for respiratory disease, all questions Aston said she and
colleagues plan to study in the future
Aston said ammonia levels also
rise when the temperatures drop — usually at night — and
spike during the winter months because of cooler temperatures.
Increase ventilation
Ventilation is key
to fighting respiratory infection from
ammonia. She noted that many producers worry about their gas
bills and reduce ventilation, inadvertently triggering a rise in ammonia levels
in the house.
Because ventilation controls
humidity, it controls ammonia, she said. The benefits of
increasing ventilation to reach acceptable ammonia levels far
outweigh the costs of saving on energy bills, she said.
“So, even if you don’t…have
an ammonia sensor — those are very expensive — you can
measure relative humidity in the house and there are target ranges,” Aston said.
“What we
recommend is anywhere from 50% to 70% humidity in the house for baby
chicks. And then, as they get older, the natural humidity will increase, and
you want to make sure you don’t go above that 70%.”
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