Aflatoxins, Heavy Metals, and Safety Issues in Dairy Feeds, Milk and Water In Some Selected Areas of Ethiopia
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Date
2018-02-03
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Addis Ababa University
Abstract
The production of wholesome milk is controlled by the quality and safety of feed supply.
Aflatoxins and heavy metals are some of the major factors that affect the quality of feeds and
water sources that are transferred and eventually get bio-accumulated in livestock species and
humans via meat, milk and milk products. Monitoring dairy production inputs using technical
tools and gathering appropriate information on perception, experience and indigenous
knowledge of stake holders along the feed and milk chains are relevant in assessing how
processing, storage and distribution of feeds and water sources to ensure safety of milk and milk
products. The objective of this study was to determine aflatoxin B1 (AFB1) in feeds and aflatoxin
M1 (AFM1) in milk and heavy metals cadmium (Cd), lead (Pb), arsenic (As) and chromium (Cr)
in feeds, water, and milk samples from West Shoa, East Shoa and Hawassa, Ethiopia. A total of
205 samples consisting of 115 concentrate feeds, 45 roughage feeds and 45milk samples were
collected for the detection and quantification of aflatoxin using Enzyme-linked Immunosorbent
Assay (ELISA). A total of 90 samples (30 feeds, 30 water and 30 milk) were collected for
determination of heavy metals using Graphite Furnace Atomic Absorption Spectrophotometer
(GFAAS). Stakeholders’ perception and experience of handling feeds and water sources were
evaluated by interviewing peri-urban farmers, feed processors, feed retailers and urban dairy
producers using semi-structured questionnaires and field observations. The results showed half
of the feed samples (81) were free from aflatoxin, and the remaining (79 samples) were within
the EU standard of 5μg/kg and the USA standard of 20μg/kg. The pattern of afltoxin
contamination showed that concentrate feeds were more contaminated (7.67 ± 0.80 μg/kg) than
roughage feeds (0.41 ± 0.14 μg/kg); hay (0.72 ± 0.25 μg/kg) was more contaminated than straw
(0.05 ± 0.05 μg/kg) and oilseed cake based concentrate feeds were more contaminated (13.09 ±
1.12 μg/kg) than concentrate feeds without oilseed cake (2.78 ± 0.66 μg/kg). The average AFB1
of feeds in Bishoftu (9.76μg/kg) was significantly higher (p<0.05) than the sampling sites in
Holetta (6.33μg/kg) and Hawassa (1.19μg/kg). The AFB1 of feeds handled by dairy producers
was significantly higher (p<0.05) (9.35 ± 1.04μg/kg) than feed retailers (6.91 ± 1.09 μg/kg) and
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feed manufacturers (7.50 ± 1.43 μg/kg). The AFM1 of milk was in a range and average of 0–
0.146 μg/L and 0.054 μg/L respectively of which 29% of the milk samples did not contain
aflatoxin, and 58% of them had AFM1 level within the EU permitted limit of 0.05μg/L and 42%
of the samples were less than the U.S.A. recommended limit of 0.5 μg/L. The AFB1and AFM1
levels of milk samples collected from the study locations were in the order of Hawassa < Holetta
< Bishoftu. With regards to heavy metals, the data showed that concentrations of heavy metals in
teff straw in Holetta and Bishoftu were 1543.54 ± 318.70 μg/kg and 1486.92 ± 279.73 μg/kg,
respectively. The overall concentration of heavy metals in teff straw was in the order of Cr > As
> Pb > Cd. The water samples taken from Mojo areas (Eastern Shoa) showed the highest of
heavy metals (43.64 μg/L - 86.89 μg/L) with very high concentration of Cr (300.56 μg/L). In
general, the average concentration of heavy metals in livestock water in Eastern shoa (Akaki to
Mojo) (28.08 ± 7.02 μg/L) was significantly higher (p<0.05) than the levels of heavy metals in
water collected from Western Shoa (Holetta/Welmera) (1.96 ± 0.28 μg/L) and the levels of the
heavy metals was in the order of Cr > As > Pb > Cd. With the exception of pH of water from
Mojo Lake (10.37) and Gelan dye factory (8.9), the rest of the water samples collected from
Bishoftu and Holetta areas were within the legal pH limit of 6.5-8.5 for livestock drinking. The
overall concentration of heavy metals in cow milk samples was in the order of Cr > Cd > Pb >
As. The concentrations of Cd and As in milk were within the permissible limits. However, 60%
and 73% of the milk samples from Holetta and Bishoftu respectively for Pb and, all the milk
samples in both study locations for Cr were above the permissible limits indicating poor quality
of milk due to environmental pollution. The data from the interview of stakeholders showed that
91% of the farmers sometimes encountered mold formation in roughage feeds due to lack of
good harvesting and stacking practices. Most of the farmers admitted to feeding light moldy
feeds to their livestock by diluting with uncontaminated ones. Most of the respondents (67%)
used extreme moldy feeds for firewood; and 33% of the interviewees damped the extreme moldy
feeds into landfills. Farmers recognized two causes of water contaminants associated with health
and production problems in livestock. Accordingly farmers from Eastern Shoa (100%) were
aware of the effect of industrial effluent as the most important hazard for dairy production;
whereas 66% of the farmers from Eastern Shoa and 34% of the respondents from Western shoa
identified leech problems in water bodies in dry season. Farmers also had indigenous knowledge
to tackle the leech problem in that 69% of the farmers used bucket for selectively scooping water
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from the water body to exclude the leech from being consumed by animals; whereas 50% of the
respondents treated animals with chopped tobacco and onion. The majority of the feed
processors (64%), feed retailers (82%) and dairy producers (56%) reported that they did not use
palate for placing their concentrate feeds implying that there is probability of mold
contamination in times of prolonged storage. Among the respondents, 88% of feed processors,
all feed retailers and most (96%) of the dairy producers recognized that wheat bran was the
most mold susceptible feed ingredient. Majority of the feed processors (67%), feed retailers
(73%) and dairy producers (58%) stored their concentrate feeds for a short period of about 1
month. Majority of the feed processors (74%), feed retailers (87%) and most dairy producers
(91%) did not encounter mold formation in their concentrate feed because of the small amount of
concentrate feed they hold and shorter storage time. To overcome mold formation in concentrate
feeds, 64% of the feed processors gave enough space between stored feed and the wall. Further
research needs to be undertaken along the feed and milk production and distribution chains
using other techniques such as HPLC, GC and multi-mycotoxin assay using LC-MS-MS taking
into account different storage conditions such as use of palate, ventilation, and duration of feed
storage on aflatoxin. The effect of mold growth in feeds on nutrient composition needs to be
investigated. There is also a need for further investigation on heavy metals from soils and fodder
feed samples grown in similar study locations.
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Keywords
Arsenic, Cadmium, Dairy Producers, Concentrate Feed, Hay, Storage Time, Mycotoxins