Lactobacillus rhamnosus GG modulates gastrointestinal absorption, excretion patterns, and toxicity in Holstein calves fed a single dose of aflatoxin B1.

The aim of the present study was to evaluate the effects of Lactobacillus rhamnosus GG (LGG; ATCC 53013) on growth performance and hepatotoxicity in calves fed a single dose of aflatoxin B1 (AFB1) and to investigate the absorption, distribution, and elimination of AFB1 and the hydroxylated metabolite aflatoxin M1 (AFM1) in rumen fluid, blood, and excretions. Twenty-four male Holstein calves were blocked for body weight and age and were randomly assigned to 1 of 3 treatment groups: (1) untreated control, (2) treated with 4.80 mg of AFB1 (AFB1 only), or (3) treated with 1 × 1010 cfu of LGG suspension and 4.80 mg of AFB1 (AFB1 plus LGG). The calves received LGG suspension in 50 mL of phosphate-buffered saline daily via oral administration for 14 d before and on the day they received a single oral dose of AFB1. Body weight was recorded at the beginning of the study (before LGG administration), at the day of AFB1 administration, and at the end of the trial. Rumen fluid, blood, urine, and feces samples were collected continuously for 96 h after AFB1 administration. Average daily gain (ADG) and plasma biochemical parameters were analyzed, and concentrations of AFB1 and AFM1 in the samples were determined for monitoring excretion pattern and toxicokinetics. The results showed that ADG was lower in AFB1-treated animals; LGG administration partially mitigated the decrease in ADG (0.85 ± 0.08 vs. 0.76 ± 0.18 kg of gain/d). The AFB1 treatment increased plasma aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase levels. Administration of LGG alleviated the AFB1-induced increase in plasma enzymes activity. The excretion patterns of AFB1 and AFM1 were surprisingly regular; toxins were rapidly detected in all samples after a single oral dose of AFB1, and the peak of toxins concentrations was sequentially reached in rumen fluid, plasma, urine, and feces (except AFM1 in rumen fluid), followed by an exponential decrease. The excretion curves showed that AFB1 and AFM1 concentrations were the highest in feces and urine, respectively. Administration of LGG decreased the concentrations of free AFB1 and AFM1 in rumen fluid and reduced the release of toxins into plasma and urine. Toxicokinetic parameters (except for the time of maximum concentration and the terminal half-life) were reduced by LGG administration. In conclusion, the absorption, distribution, and excretion of AFB1 and AFM1 were rapid in calves fed a single dose of AFB1. Urine was the main route for the excretion of AFM1, and the clearance pattern from the peak of concentration was well fitted by exponential decreasing function. Administration of LGG reduced the absorption of AFB1 in the gastrointestinal tract by increasing the excretion via the feces, thus alleviating the hepatotoxic effect of AFB1.

Excretion pattern of aflatoxin M1 in milk of goats fed a single dose of aflatoxin B1.

The feedstuffs used in dairy animals must be able to give consumers confidence about the wholesomeness of milk with regard to aflatoxin contamination. The aim of this study was to determine the excretion patterns of aflatoxin M(1) (AFM1) in the milk of dairy goats fed a single dose of pure aflatoxin B(1) (AFB1), which can occasionally occur if feeds are infected by hot-spot growth of molds that produce aflatoxins. Five dairy goats in midlactation were administered 0.8 mg of AFB1 orally. Individual milk samples were collected for 84 h after AFB1 dosage. Aflatoxin M(1) was found in milk in the highest concentration. In all goats, AFM1 was not detected in milk before AFB1 administration, but was detected in the first milking following AFB1 administration. The excretion pattern of AFM1 concentration in milk was very similar in all goats even if the values of the concentration differed between animals. The peak values for AFM1 concentration in milk was observed in milk collected during the milking at 3 and 6h. After the peak, the AFM1 in milk disappeared with a trend that fitted well a monoexponential decreasing function, and the toxin was not detected after 84 h. Only about 0.17% of the amount of AFB1 administered was detected as AFM1 in milk, and about 50% of this was excreted in the first liter of milk yielded after AFB1 intake. Correct procedures to prevent growth of molds, and consequent AFB1 contamination, on the feedstuffs for lactating goats represent the key to providing consumers a guarantee that milk is not contaminated by AFM1.

A simple steady-state model for carry-over of aflatoxins from feed to cow's milk.

A simple steady-state model is derived from two kinetic one-compartment models for the disposition of aflatoxin B1 (AFB1) and aflatoxin M1 (AFM1) in the lactating cow. The model relates daily intake of AFB1 in feed of dairy cattle and the cow's lactation status to resulting concentrations of AFM1 in milk. Moreover, assuming a linear relationship between the cow's lactation status and feed intake, the model relates daily milk production and AFB1 concentration in total feed to AFM1 levels in milk. The model explains similar experimental outcomes from different investigations into carry-over of aflatoxins from feed to milk. Although it is difficult to set a permanent limit for AFB1 in feed, the European Union (EU) limit of 5 microg AFB1 kg(-1) concentrate has proved, thus far, to be an appropriate level in preventing the EU limit of 0.05 microg AFM1 kg(-1) milk being exceeded.

Aflatoxin M1 absorption and cytotoxicity on human intestinal in vitro model.

Aflatoxin M1 (AFM1) is the principal hydroxylated Aflatoxin B1 (AFB1) metabolite and is detected in milk of mammals, after consumption of feed contaminated with AFB1. As it is classified as probable human carcinogen (group 2B of the IARC), most countries have regulated its maximum allowed levels in milk in order to reduce AFM1 risk (50 ng/kg the EU and 500 ng/kg in the USA). It was demonstrated that if AFB1 must be converted into its reactive epoxide to exert its effects, and the protein binding may play an important role in its cytotoxicity. Conversely, the AFM1 epoxidation in human liver microsomes is very limited and studies with human cell line (MCL5), expressing or not expressing cytochrome P450 enzymes, demonstrated a direct toxic potential of AFM1 in absence of metabolic activation. For this reason, while AFM1 is generally considered a detoxification product of AFB1 relatively to carcinogenicity and mutagenicity property, this is not always true for cytotoxicity activity. Aim of this work is to evaluate the intestinal absorption of AFM1 using a human in vitro model, the Caco-2 cell line. Either the parental Caco-2 cell line or its derived clone TC7, with higher metabolic competence, have been used. They were treated with different concentrations of AFM1, that mirror the milk contamination level (0.3-32 nM corresponding to 10-10,000 ng/kg), either in undifferentiated or in differentiated phase of growth. After 48 h of treatment in serum free medium, a dose dependent absorption of AFM1 has been detected in both cell lines, especially in differentiated cells, while, no appreciable effects on cell viability were observed, except for a general cellular suffering, revealed by LDH release, particularly evident in the undifferentiated cells. As well, no metabolites or AFM1 conjugates have been detected. The present results may be crucial for the evaluation of human risk to AFM1 exposure, in particular for children's population, due to their large use of milk and derivatives.

Transfer of aflatoxin B1 from feed to milk and from milk to curd and whey in dairy sheep fed artificially contaminated concentrates.

An experiment was carried out using dairy ewes to study the transfer of aflatoxin B1 (AFB1) from feed to milk and from milk to cheese. The effects of AFB1 on liver function and hematological parameters were also investigated. Fifteen ewes were assigned to treatments in replicated 3 x 3 Latin squares. The experimental groups received 32, 64, or 128 microg/d of pure AFB1 for 7 d followed by 5 d of clearance. On the sixth day of the first period, the total daily milk produced by each ewe was collected separately and processed into cheese. The results indicate that the level of AFB1 used did not adversely affect animal health and milk production traits. The aflatoxin M1 (AFM1) concentrations in milk approached a steady-state condition in all treated groups between 2 and 7 d after the start of treatment. The mean AFM1 concentrations of treated groups in steady-state condition (184.4, 324.7, and 596.9 ng/kg in ewes fed 32, 64, or 128 microg of AFB1, respectively) were significantly affected by the AFB1 doses. The AFM1 concentration was linearly related to the AFB1 intake/kg of BW. The carry-over values of AFB1 from feed into AFM1 in milk (0.26 to 0.33%) were not influenced by the AFB1 doses. The AFM1 concentrations in curd and whey were linearly related to the AFM1 concentrations in the unprocessed milk.

Excretion of aflatoxin M1 in milk of dairy ewes treated with different doses of aflatoxin B1.

Two experiments were conducted to study the amount of aflatoxin M1 (AFM1) in milk in response to feeding aflatoxin B1 (AFB1). In experiment 1, four dairy ewes in early lactation received a single dose of pure AFB1 (2 mg). Individual milk samples were collected during the following 5 d to measure AFM1 concentration. The average excretion of AFM1 in milk followed an exponential decreasing pattern, with two intermediate peaks at 24 and 48 h. No AFM1 was detected in milk at 96 h after dosing. The mean rate of transfer of AFB1 into AFM1 in milk was 0.032%, with a high individual variability (SD = 0.017%). In experiment 2, 16 dairy ewes in midlactation were divided into four groups that received different daily doses of AFB1 (0, 32, 64, and 128 microgram for control and groups T1, T2, and T3, respectively) for 14 d. Pure AFB1 was administered to each animal divided in two daily doses. Individual milk samples were collected at 12, 24, 36, 48, 72, 96, 144, 216, and 312 h after the first AFB1 administration, during the intoxication period, and every 24 h for 7 d after the withdrawal of AFB1. AFM1 was detected in the milk of all animals of the treated groups at 12 h after the administration of AFB1. In all treated groups, milk AFM1 concentration increased from 12 to 144 h after the beginning of administration. It then decreased, reaching a stable concentration at 216 and 312 h after the first administration. No AFM1 was detected in milk 3 d after the last administration of AFB1. Milk AFM1 concentration measured at steady-state condition was significantly affected by the AFB1 dose (0.031, 0.095, and 0.166 in T1, T2, and T3 groups, respectively), with a linear relationship between AFB1 dose and milk AFM1 concentration (R2 = 77.2%). The carryover (AFM1/AFB1 ratio) was not significantly affected by treatment, and its mean value was 0.112% (SE = 0.011). The carryover was lower than that reported for dairy cattle and goats, suggesting a better ability of sheep to degrade AFB1.