Page 1056 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

988 SECTION | XV Mycotoxins

VetBooks.ir Other biotransformation products of AFB 1 are AFQ 1 , calculate the dietary:milk ratio for AFs and is an accurate
predictor. To compare with other mammalian species,
which can be metabolized to AFH 1 . AFB 1 is also metabo-
humans excrete 0.09% 0.43% of dietary AFB 1 intake as
lized to AFP 1 , AFM 1 , aflatoxicol and other metabolites.
The AFP 1 , AFM 1 , AFQ 1 and aflatoxicol form glucuronide AFM 1 in breast milk, sheep excrete 0.26% 0.33% of the
and sulfate conjugates. dietary AFB 1 as AFM 1 in the milk, and AFs in sows’ milk
have been shown to be B1000-fold less that the AFs in
Turkeys are a sensitive species and they activate AFB 1
3.5 times more than chickens by hepatic enzymes homo- the diet (Zarba et al., 1992; Silvotti et al., 1997; Battacone
logs to human CYP1A2, CYP1A5 and other CYPs to et al., 2009). The dietary threshold for AF excretion in
form AFB 1 -8,9-epoxide. Younger birds activate AFB 1 at cows’ milk appears to be B15 ppb dietary level or 230 μg
a greater rate than older birds. Conjugation of the AFB 1 - AFB 1 /cow/day. AFs in milk generally disappear within
8,9-epoxide by GSH is generally considered to be the 24 72 h after all the AFs have been removed from the
diet. The percentage of AFs in milk increases with increas-
rate-limited determinant in species susceptibility to AFB 1
rather than the rate at which AFB 1 -8,9-epoxide is formed. ing milk yields. Cows in early lactation can excrete from
The affinity of the glutathione S-transferases for AFB 1 - 3.8% to 6.2% of the dietary AFB 1 as AFM 1 in the milk,
8,9-epoxide is also important. Cattle were given single and cows in late lactation can excrete 1.8% to 2.5% of die-
oral doses (ranging from 0.2 mg, 0.4 mg, 0.6 mg, and tary AFB 1 as AFM 1 . This phenomenon appears to be
0.8 mg/kg body weight) of AFs from rice culture (42% linked to cows having upregulation of AFB 1 metabolism
AFB 1 and 27% AFB 2 ) in gelatin capsules (Cook et al., during early lactation. Sheep and swine excrete AFs in
1986). AFM 1 was identified in rumen contents 2 h after milk. Sheep excreted 0.26% to 0.33% of the dose of AFB 1
dosing. This observation suggests that AFM 1 is formed by as AFM 1 in milk. AF level in curds is two times higher
the flora and fauna in the rumen. Urine from these cattle than whole milk (Battacone et al., 2005). AFs are excreted
contained AFB 1 and AFM 1 . Bovine hepatocytes metabo- in sows’ milk (Silvotti et al., 1997). The levels of AFs in
lized AFB 1 to AFM 1 , AFB 1 dihydrodiol and minor levels sows’ milk increased over a 25-day lactation period. The
of AFB 1 glutathione conjugate. Pretreatment of goats sows were fed diets containing 800 ppb AFB 1 or a diet
with phenylbutazone and benzoflavones increased the tox- containing 400 ppb AFB 1 1 400 ppb AFG 1 for the entire
icity of AFB 1 . Hepatic Kupffer and endothelial cells in gestation and lactation period. The average ratio of AFs in
the rat have been shown to have upregulated activity of the diet to AFs in milk was B1000:1. Sows fed diets con-
enzymes that convert AFB 1 to AFM 1 (Gemechu-Hatewu taining 800 ppb AFB 1 or 400 ppb AFB 1 1 400 ppb AFG 1
et al., 1996). The P450 inducers used were phenobarbitol, excreted AFB 1 or AFB 1 1 AFG 1 , respectively. Sows fed
isosafrole, Aroclor 1254, and 3-methylcholanthrene. AFB 1 excreted AFM 1 and sows fed AFB 1 1 AFG 1
AFs are excreted in milk, eggs, urine, semen, bile, and excreted AFM 1 1 AFM 2 metabolites. The consensus in the
scientific literature is that AFs are stable in milk (Becker-
feces. Bingham et al. (2004) identified AFM 1 and AFP 1
in dog urine. AFB 1 , AFM 1 , and aflatoxicol are transferred Algeri et al., 2016). Approximately 75% of AFs in milk
to the egg. Humans exposed to dietary AFs excrete are found in the casein (protein) fraction and 25% in the
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ABM 1 , AFP 1 , and AFB 1 -N -Guanine in urine. AFs have whey fraction of milk. AFs are also found in butter and the
been shown to be excreted in boar semen. Rats excrete division is B84% in butter milk and B16% in butter. AFs
AFB 1 into the intestinal tract via bile and the intestinal are concentrated in cheese, and the concentration factor
mucosa also excretes AFs. Cattle excrete AFB 1 predomi- varies with the type of cheese and cheese-making
nately in the feces and AFM1 predominately in the urine procedures.
(Stubblefield et al., 1983).
Residues in Meat and Eggs
Aflatoxins in Milk
Chickens were fed a diet containing rice culture that
AFs can be present in milk and processed milk products AGB 1 produced by A. parasiticus (Pandey and Chauhan,
(Becker-Algeri et al., 2016). Milk products such as cheese 2007). At 2 weeks of age groups of birds were placed on
and dried milk also can become directly contaminated diets containing 0.0, 2.5, 3.13, and 3.91 ppm AFB 1 ,
with AFs by fungal growth in these substrates. AFs appear respectively. These diets were fed for 40 weeks. Tissues
in cows’ milk within 12 48 h after ingestion. The percent- and eggs were collected on day 40 for AF analyses. AFB 1
age of dietary AFs being excreted in milk varies from in eggs increased with feed levels, the mean levels were
0.17% to 3%. Veldman et al. (1992) derived the formula 1.43, 1.39, and 1.63 ppb, respectively, for the different
for excretion of AFM 1 in milk as (ng AFM 1 /kg treatment groups. AFB 1 levels in breast meat were 18, 26,
milk 5 1.19 3 dietary intake of μg AFB 1 /day/ cow 1 1.9). and 26 ppb, respectively, for the chickens in the different
Alternatively, herd-specific analytical data can be used to treatment groups. The levels of AF metabolites were not