PoultryUSA - May 2018 - 15
Salmonella recovery from multiple inoculation routes
Generally, catch crew workers wear respiratory
protective equipment during harvest (catching) to
minimize the amount of dust they inhale. However,
the birds themselves do not have any external respiratory protection other than the increased mechanical
exhaust ventilation during harvest. Therefore, there is
potential for increased levels of dust in the air to be
inhaled by the broilers during catching and accumulate in the respiratory tract.
The levels of dust present during catching may
depend on the outside ambient temperature. During
hot weather, ventilation rates are at maximum levels to
prevent bird heat stress. However, during cold weather
ventilation rates are at lower levels to prevent bird
chilling. This difference in ventilation could affect levels of dust present during broiler catching.
Although it would seem increased ventilation
would decrease dust, it is possible increased ventilation rates combined with increased bird activity during harvest may cause resuspension of dust particles.
Research shows that greater levels of E. coli were
detected in air from tunnel-ventilated broiler houses
during the summer when ventilation rates were higher
in comparison to lower winter ventilation rates.
Source: Data adapted from E.V. Chadwick M.S. Thesis, Auburn University
Salmonella is found at the highest percentage when broilers are
inoculated in the trachea.
chicks and result in intestinal colonization.
An in vitro tracheal clearance assay reported a
clearance velocity of 2.39 millimeters per minute
for chicken embryos. Using this clearance rate, the
entire broiler trachea would clear every 1.05 minutes.
Tracheal clearance of dust inhaled during catching
may have led to the general decrease in respiratory
tract bacteria during harvest.
Read more: 3 tools to control
Research on tracheal response
to bacterial infection
In a study where broiler respiratory tracts were
sampled one week prior to harvest, one day prior to
harvest and during harvest, there was a trend of decreasing Salmonella and Enterobacteriaceae prevalence even during catching when dust levels were
expected to be higher than normal.
This decrease in respiratory tract bacteria was unexpected considering the increases in dust during harvest.
The mucus and cilia lining the trachea are continuously
removing dust particles, bacteria and toxins from the air
where they are swallowed and enter the esophagus. This
mucus coating may aid the passage through the acid environments of the proventriculus and gizzard of young
reactivated Salmonella in poultry feed,
The broiler respiratory tract appears to be an important potential route for Salmonella dissemination in a
growout house. However, the exposure of broilers to dust
during harvest may not lead to significant levels of carcass contamination. Based on this information, steps to
minimize the presence of dust during the growout period
could potentially decrease levels of Salmonella contamination within the house and therefore decrease the levels
of Salmonella entering the processing plant. ■
References available on request
Dr. Dianna Bourassa is an assistant Professor of Poultry Science at Auburn University specializing in poultry
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