The development and significance of fungi in poultry rearing sheds : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology at Massey University
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Date
1984
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Massey University
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Abstract
A study was conducted at the Poultry Research Centre, Massey
University, to determine the numbers, types and patterns of development
of fungi that occur in poultry rearing sheds. Two sheds, a broiler shed
and a layer shed were analysed for the fungal population by weekly sampling
of litter, feed and air. Particular emphasis was placed on the
presence of Penicillium and Aspergillus as these genera contain species
of potential significance to flock health as infectious or toxigenic
agents. Use of the dilution plating method with modified Potato
Dextrose Agar and Aspergillus Differential Medium for culture resulted
in successful isolation of these genera. Further selectivity was
attained with the use of a modification of the strip-bait method of
Luttrell (1967}. Air sampling was by the exposed agar plate method.
The poultry houses were found to contain high levels of viable fungal
propagules. Of the total fungi, Penicillium, Aspergillus and
Scopulariopsis were the major genera. Other genera included Rhizopus,
Mucor, Cladosporium and Geotrichum. Penicillium was found throughout
the trials. Scopulariopsis was present at low levels in fresh litter
and feed but counts increased greatly with time. Counts of species of
Aspergillus, (A. flavus and A. fumigatus) also showed increases
mainly towards the end of the trials. Other genera (Geotrichum,
Cladosporium etc.) were found on certain days only.
As litter aged, its pH and moisture content increased and these
increases were correlated to the increase in total fungal numbers during
the period of housing. Patterns of fungal succession in the litter were
similar to those in air. For some species the increases in numbers in
litter were preceded by a similar peak in the air (eg. A. flavus)
whereas for others the peak in litter was earlier than the peak in air
(S. brevicaulis). The correlation between patterns in air and those in
feed and litter was more obvious in the layer shed, where a more active
flock created greater air movement than in the broiler shed where the
birds were docile and caused very little circulation of air.
A. flavus isolates were screened for the production of aflatoxin on
coconut agar. Approximately 30% of all A. flavus isolates tested were
toxigenic. Also, it was possible to extract the toxin after growth in
semisynthetic liquid medium from isolates which had been strongly fluorescent
on coconut agar, but not those which had been weakly fluorescent.
Feed and litter samples tested for the presence of aflatoxin and
other mycotoxins (T-2, ochratoxin and zearalenone) were negative for
these mycotoxins.
The fungal population of poultry houses has been shown to include
species which may be of economic importance. The large amounts of
A. flavus (potentially toxigenic) and A. fumigatus (infectious), in
particular, should not be ignored as they may well affect poultry health
and productivity.
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Keywords
Poultry housing, Feed and feeding, Pathogenic fungi