IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC ...

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IARC MONOGRAPHS VOLUME 82
diet and controls received only the basal diet (Table 14). Ten fish were removed from
each tank for histopathological evaluation at four and eight months and the remaining
fish were held for 12 months. Liver nodules of doubtful classification and five randomly
sampled livers at each sampling date were examined histopathologically. At eight
months, fish fed contaminated untreated corn had a high incidence (19/20) of hepatoma
(Brekke et al., 1977). Ammoniation significantly reduced the carcinogenic potential at 12
months of aflatoxin B 1-contaminated corn (Table 14).
Table 14. Incidence of hepatoma in trout fed various
diets for 12 months
Diet Incidence of hepatoma
Basal diet 1/116
Uncontaminated corn untreated 2/115
Uncontaminated ammonia-treated corn 0/111
Contaminated corn untreated 109/112
Contaminated ammonia-treated corn 3/116
From Brekke et al. (1977)
In a more recent experiment, trout were given non-fat dried milk power prepared
from the milk of cows that had received aflatoxin-contaminated diets. Thirty lactating
cows (Holstein-Friesian) were fed a ration containing ammonia-treated (atmospheric
pressure at ambient temperature; AP/AT) aflatoxin-contaminated whole cottonseed (aflatoxin
B 1, 5200 μg/kg) for seven days followed by an untreated aflatoxin-containing seed
for seven days. The final aflatoxin B 1 concentration in the cow ration was 780 μg/kg. In
a second experiment, three lactating cows were fed for 10 days a ration containing
ammonia-treated (high pressure at high temperature; HP/HT) aflatoxin-contaminated
cottonseed (aflatoxin B 1, 1200 μg/kg), incorporated at 25% (w/w) of the total dry weight
of the ration. Then, they were fed for 10 days a ration containing untreated aflatoxincontaminated
cottonseed (aflatoxin B 1, 1200 μg/kg), incorporated at 25% (aflatoxin B 1,
300 μg/kg, in final ration). Milk was collected daily from days 3 to 7 (for each period)
when cows were fed the AP/AT material and from days 3 to 10 (for each period) when
they were fed the HP/HT material. The milk was processed to prepare non-fat dried milk
powder, which was fed as 25% of the diet to rainbow trout (Oncorhynchus mykiss) for
12 months. The aflatoxin M 1 levels in the milk powders from cows given untreated and
treated seed were: AP/AT, 85 and < 0.05 μg/kg; and HP/HT, 32 and < 0.05 μg/kg, respectively.
AP/AT treatment reduced the liver tumour incidence to 2.5% compared with 42%
in the trout fed the milk from the cows that received the untreated cottonseed. In positive
controls, feeding aflatoxin B 1 (4 μg/kg) continuously for 12 months resulted in a 34%
tumour incidence, while feeding for two weeks a diet containing 20 μg/kg aflatoxin B 1
resulted in an incidence of 37% of liver tumours, and feeding of 80 μg/kg or 800 μg/kg