By determining the numbers of bacteria in the poultry production
environment, improved air ventilation was identified as a prime management
practice in preventing "hot spots" of 
Salmonella and E.coli multiplication
in broiler litter or layer manure. The prevention of water leakage
was also identified as another important flock health and quality assurance
practice.
The study further corroborated: 1) the relationship between litter/manure
humidity and moisture control with the reduction of Salmonella contamination
on farms; and 2) that contamination is not uniformly distributed throughout
the house but instead, is mainly located in areas that are favorable for
bacterial multiplication. A variety of ventilation options are proposed
to ensure that air is gently and uniformly distributed at the velocity
of 100 feet or more per minute over and in close proximity to all litter
and manure surfaces to achieve drier litter/manure and healthier, safer
birds.
In this study, the numbers of Salmonella and E.coli in
litter/manure related to low levels of humidity (relative humidity of Aw)
and moisture content (MC). Drag swabs and individual litter cultures
confirmed that high Aw levels (>90 percent) were associated with a higher
prevalence of Salmonella if introduced, and E.coli.
Furthermore. culture of litter revealed higher Salmonella populations
in litter samples possessing MC levels above 35 percent and Aw values ranging
from 0.9 to 0.95.
Additionally, a quantitative direct relationship between ventilation
rates and higher or lower levels of humidity and moisture in 
poultry litter/manure
and Salmonella/E.coli loads in the litter was observed. Very
low litter surface airflow rates (<60 feet/minute) tended to be associated
with higher E.coli counts in broiler litter as opposed to elevated
airflow rates (>60 fpm), which were associated with reduced E.coli
populations. A clear cut trend for Salmonella was not established
for broiler litter due to the large number of Salmonella negative
samples. However, clearly higher Salmonella counts were observed
in layer manure pits away from the fans with very low airflow rates.
For those commercial broiler houses surveyed, decreased airflow was significantly
associated with high MC (av. 41.2 percent) and Aw (av. 0.909). Conversely
elevated airflow was associated with lower MC (av. 29.6 percent) and Aw
(av.0.849).
In laboratory studies on the persistence of Salmonella in litter,
used poultry litter was seeded with Salmonella typhimurium, thoroughly
stirred, stored at room temperature and tested weekly for Salmonella.
Salmonella persisted through the seventh week in the litter by
usual culture methods. From eight to 10 weeks, the organism was only
isolated by the delayed secondary enrichment procedure, suggesting that
Salmonella may survive in the litter in reduced numbers. In
a second laboratory study, we were unable to verify that Aw levels play
a vital role in the survival and multiplication of Salmonella.
This study suggests that elevated water parameters (Aw 0.9 to 0.95 and
MC above 35 percent) may aid in the persistence of and promote large Salmonella
and E.coli populations in poultry houses. Modest improvements
in ventilation that ensure all little/manure surfaces have an airflow rate
>100 feet per minute may be important in maintaining drier litter/manure,
thus creating an adverse environment for the growth of food -borne pathogens.
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Summaries of completed projects are available at http://www.poultryegg.org
