Citation
Azman, Nur Izzati
(2020)
Prevalence of aflatoxigenic fungi and aflatoxins on commercial and formulated goat's feed, and aflatoxin M1 carryover in goat's milk.
Masters thesis, Universiti Putra Malaysia.
Abstract
At present, the consumers’ preference over cow’s milk has steadily shifted
towards goat’s milk due to its many newly-found benefits. In Malaysia, largescale
commercial goat’s milk production is still relatively new and mainly
managed by the small and medium enterprises (SMEs). Among the major
problems faced by Malaysian goat farmers is feed contamination by the
aflatoxigenic Aspergillus flavus and A. parasiticus. The hot and humid climate of
Malaysia further exacerbates the fungal proliferation which leads to the
production of aflatoxins, especially aflatoxin B1 (AFB1). Upon ingestion, AFB1 is
bio-transformed into AFM1 which is transferrable to infants during breastfeeding.
AFM1 causes stunted growth and delayed development in infants and children.
Although worldwide surveillance studies have been done on AFM1
contamination in milk and milk products, Malaysian-based data are scarce.
Furthermore, with the booming of goat’s milk industry in Malaysia, numerous
researches are being conducted, including feed formulation, for the goats’ health
improvement and maintenance. Nevertheless, the safety and quality of the
formulated feed must still be ensured. Therefore, the objectives of the present
work were (i) to determine the prevalence of aflatoxigenic Aspergillus spp. on
commercial and formulated goat’s feed samples; (ii) to determine the occurrence
of aflatoxins present in commercial and formulated goat’s feeds; and (iii) to
determine the occurrence of aflatoxin M1 present in goat’s milk samples and to
establish the relationship between AFB1 present in commercial and formulated
goat’s feeds and their carryover rate in goat’s milk as AFM1. Three commercial
goat farms (Farms A, B, C) were selected to supply the commercial goat’s feed
and goat’s milk over a period of three months (i.e., does’ common lactation
period), while one farm involved in novel feed formulation was selected to supply
the formulated goat’s feed and goat’s milk. The total number of goat’s feed
samples was 60, and goat’s milk 120. Enumeration of fungal loads using
Dichloran Rose Bengal Chloramphenicol agar showed that Farm C goat’s
concentrate sample yielded the highest total fungal load at log 7.071 ± 0.03
CFU/g. Fungal identification on Aspergillus flavus and A. parasiticus agar
revealed that 48.33% (n = 29 of 60) feed samples were positive for A. flavus and
A. parasiticus with goat’s concentrate from Farm B yielded the highest load of
A. flavus and A. parasiticus at log 3.206 ± 0.05 CFU/g. Enzyme-linked immuneassay
(ELISA) was performed to quantify total aflatoxins in goat’s feed, and
AFM1 in goat’s milk, while high performance liquid chromatography (HPLC) was
used to quantify AFB1, AFB2, AFG1, and AFG2 in goat’s feed, and AFM1 in goat’s
milk. ELISA results revealed that 76.67% (n = 46 of 60) goat’s feed samples
were contaminated with total aflatoxins (0.050 to 4.658 ng/g), while HPLC results
revealed that 11.67% (n = 7 of 60) goat’s feed samples were contaminated with
AFB1 (0.139 to 28.18 ng/g), AFB2 (6.78 ng/g), and AFG1 (1.71 to 54.99 ng/g).
AFG2 was not detected. One feed sample from Farm A was found with AFB1
higher than the maximum European Union (EU) regulatory limit. Comparing to
the other farms, Farm A generally had higher aflatoxin contamination. High
relative humidity and temperature during sampling at Farm A could have led to
this contamination as these ecophysiological factors are conducive for aflatoxin
production by Aspergillus spp. ELISA results further revealed that 46.67% (n =
56 of 120) goat’s milk samples were positive for AFM1 (0.052 to 0.177 ng/mL),
while HPLC revealed that no goat’s milk sample was contaminated with AFM1.
Following the positive results of AFM1 in goat’s milk samples, the AFB1 in goat’s
feed from the same week when the milk was sampled was obtained, and the
carryover rate of AFM1 was estimated. The carryover efficiency from AFB1 in
feed into AFM1 in milk was found within the range of 0.12 to 11.54%. The amount
of AFM1 detected in goat’s milk samples did not exceed the Malaysian regulatory
limit of 0.5 ng/mL, but exceeded the EU regulatory limit of 0.5 ng/mL.
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