| dc.description.abstract | The occurrence of fungi and their toxins in poultry feed
lowers the hygienic quality of feed and presents several hazards to
poultry and sometimes to 'man. To evaluate the magnitude of these
hazards and generally the hygienic quality of feed presented to
poultry in Nairobi, Kenya, several experiments were carried out. A
total of 90 samples of poultry feeds were randomly sampled from
farmers in peri-urban areas Nairobi province and in Kikuyu division
of Kiambu district. dirty samples were collected in January, 30 in
March, and 30 in May 1993.
All the samples were subjected to moisture determination,
mycological examination and mycotoxin analysis. Enumeration of
total mould counts, Aspergillus spp. counts, Penicillium spp.
counts, Fusarium spp. counts as well as identification of isolates
of species belonging to these three genera was done. The aflatoxin
producing ability of the Aspergillus flavus group isolates was
tested on a synthetic medium. All feed samples were also analysed
for aflatoxin B1, B2, G1, G2, ochratoxin A, zearalenone and
sterigmatocystin.
The total mould counts recorded were very high compared to
the findings from other parts of the World such as Norway and
Germany. They varied from 1 X 104 - 1.31 X 106 CFU/g. On the basis
of these mould counts, the hygienic quality of 36%- of all the
samples examined were classified as unacceptable. Aspergillus spp. ,
Penicillium spp. and Fusarium spp. were the most commonly isolated
fungi sometimes accounting for all the fungi identified.
Aspergillus spp. counts varied from 1.0 X 103 - 8 X 105. Penicillium
spp. counts varied from 2.0 X 102 - 3.0 X 105 while Fusarium spp.
counts varied from 0 - 3.1 X 105• A total of fifteen species of the
genus Aspergillus, 19 of Penicillium and 3 of Fusarium were
identified. Overall, Aspergill us flavus was the most commonly
isolated species being demonstrated in 73.3% of all samples. When
the aflatoxin producing ability of these A. flavus group isolates
was tested on yeast extract sucrose agar, only 19.01% of all the
isolates produced aflatoxins.
Analysis of mycotoxins by thin layer chromatography revealed
that 35.6% of all the samples were contaminated with at least one
of the seven mycotoxins analysed for, with aflatoxins being the
most abundant. They were found in 24.4% of the samples at levels of
between trace and 50ppb. Ochratoxin A was detected in 10% of all
samples, zearalenone in 5.6% and sterigmatocystin in 2.2% of all
samples examined. Occurrence of several mycotoxins in one sample
was recorded in 13.3% of all the samples. The moisture content
varied from 6.79 % to 11.46 %.
Statistical analysis showed no significant differences in the
levels of total mould counts, moisture content, mycotoxin
contamination and most fungal groups' counts in feed samples from
different manufacturers or of different feed formulations. However,
almost all these variables showed significant differences when feed
sampled at different times was compared.
Several conclusions are drawn from this study. (1) The level
of fungal contamination of poultry feeds used in Nairobi is very
high making most of the poultry feed unacceptable. (2) The majority
of these contaminants belong to the genera Aspergillus, Penicillium
and Fusarium and include many well known mycotoxigenic fungi
species. (3) Aflatoxins are present in some of the feed used in
Nairobi and surrounding areas, but at levels insufficient to cause
clinical aflatoxicosis. (4) Mycotoxin other than aflatoxins, such
as ochratoxin A, zearalenone and sterigmatocystin also occur in
poultry feeds used in Kenya, sometimes as co-contaminants to the
aflatoxins. (5) The frequency of contamination of poultry feed with
mycotoxins vary with the month of the year. (6) Because of the low
moisture content of feed recorded in this study, the mycotoxin
contamination in mixed poultry feed is most likely as a result of
use of contaminated raw materials and not due to fungal growth and
toxin production in the mixed feed. For this reason, it is
recommended that further studies be done to identify the most
susceptible raw material and also have a continuous surveillance
for mycotoxins in these raw materials. | en |
