Carry-over of pyrrolizidine alkaloids from feed to milk in dairy cows

Pyrrolizidine alkaloids are toxins present in many plants belonging to the families of Asteraceae, Boraginaceae and Fabaceae. Particularly notorious are pyrrolizidine alkaloids present in ragwort species (Senecio), which are held responsible for hepatic disease in horses and cows and may lead to the death of the affected animals. In addition, these compounds may be transferred to edible products of animal origin and as such be a threat for the health of consumers. To investigate the possible transfer of pyrrolizidine alkaloids from contaminated feed to milk, cows were put on a ration for 3 weeks with increasing amounts (50-200 g day(-1)) of dried ragwort. Milk was collected and sampled twice a day; faeces and urine twice a week. For milk, a dose-related appearance of pyrrolizidine alkaloids was found. Jacoline was the major component in milk despite being a minor component in the ragwort material. Practically no N-oxides were observed in milk, notwithstanding the fact that they constituted over 80% of the pyrrolizidine alkaloids in ragwort. The overall carry-over of the pyrrolizidine alkaloids was estimated to be only around 0.1%, but for jacoline 4%. Notwithstanding the low overall carry-over, this may be relevant for consumer health considering the genotoxic and carcinogenic properties demonstrated for some of these compounds. Analysis of the faeces and urine samples indicated that substantial metabolism of pyrrolizidine alkaloids is taking place. The toxicity and potential transfer of metabolites to milk is unknown and remains to be investigated.

Proficiency studies on the determination of paralytic shellfish poisoning toxins in shellfish

Paralytic shellfish poisoning toxins are produced by dinoflagellates. Shellfish filtering these unicellular algae will accumulate the toxins and pose a health risk when consumed by man. In the European Union, paralytic shellfish poisoning toxins in bivalve molluscs are regulated at a maximum content of 80 microg/100 g (91/492/EEC). The current reference method in the European Union is the mouse bioassay, but alternative methods including the liquid chromatography methodology are preferred for ethical reasons. Analyses of suspected shellfish batches revealed, however, unacceptable differences in results reported by a small group of Dutch laboratories all using liquid chromatography methods with precolumn derivatization, followed by fluorescence detection. Therefore, a series of proficiency studies were undertaken among these laboratories. In the first three studies, participants were more or less allowed their own choice of method execution details. This approach yielded unsatisfactory results. A fourth study was then initiated in which a standardized method was mandatory. Two types of test material were used in the fourth study: lyophilized Cardium tuberculatum material containing saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX), and lyophilized mussel material containing dc-STX. The latter material was investigated in an interlaboratory study involving 15 participants and was considered as the reference material. Among the four laboratories, coefficients of variation (ANOVA) for C. tuberculatum material were 10% (n = 11) and 9% (n = 12) for STX and dc-STX, respectively, and for the reference material was 8% (n = 12) for dc-STX. The joint efforts showed that variability in analysis results between laboratories that all apply more or less the same method can be drastically improved if the methodology is rigorously standardized.

Effects ofFusariumtoxin-contaminated wheat and feed intake level on the biotransformation and carry-over of deoxynivalenol in dairy cows

An experiment was carried out to examine the effects of feeding Fusarium toxin-contaminated wheat (8.21 mg deoxynivalenol (DON) and 0.09 mg zearalenone (ZON) per kg dry matter) at different feed intake levels on the biotransformation and carry-over of DON in dairy cows. For this purpose, 14 ruminal and duodenal fistulated dairy cows were fed a diet containing 60% concentrate with a wheat portion of 55% (Fusarium toxin-contaminated wheat (mycotoxin period) or control wheat (control period)) and the ration was completed with maize- and grass silage (50 : 50) on a dry matter basis. Daily DON intakes ranged from 16.6 to 75.6 mg in the mycotoxin period at dry matter intakes of 5.6-20.5 kg. DON was almost completely biotransformed to de-epoxy DON (94-99%) independent of the DON/feed intake, and the flow of DON and de-epoxy DON at the duodenum related to DON intake ranged from 12 to 77% when the Fusarium toxin-contaminated wheat was fed. In the serum samples, de-epoxy DON was detected in the range of 4-28 ng ml-1 in the mycotoxin period, while concentrations of DON were all below the detection limit. The daily excretion of DON and de-epoxy DON in the milk of cows fed the contaminated wheat varied between 1 and 10 microg and between 14 and 104 microg, respectively. The total carry-over rates as the ratio between the daily excretion of DON and de-epoxy DON into milk and DON intake were in the ranges of 0.0001-0.0002 and 0.0004-0.0024, respectively. Total carry-over rates of DON as DON and de-epoxy DON into the milk increased significantly with increasing milk yield. In the urine samples, de-epoxy DON was the predominant substance as compared with DON with a portion of the total DON plus de-epoxy DON concentration to 96% when the Fusarium toxin-contaminated wheat was fed, whereas the total residues of DON plus de-epoxy DON in faeces ranged between 2 and 18% of DON intake in the mycotoxin period. The degree of glucuronidation of de-epoxy DON was found to be approximately 100% in serum. From 33 to 80% of DON and from 73 to 92% of de-epoxy DON, and from 21 to 92% of DON and from 86 to 100% of de-epoxy DON were glucuronidated in the milk and urine, respectively. It is concluded that DON is very rapidly biotransformed to de-epoxy DON in the rumen and only negligible amounts of DON and de-epoxy DON were transmitted into the milk within the range of 5.6-20.5 kg day-1 dry matter intake and milk yields (fat corrected milk) between 10 and 42 kg day-1.

Aflatoxin M1in milk powders: Processing, homogeneity and stability testing of certified reference materials

As part of the certification campaign of three candidate reference materials for the determination of aflatoxin M1 (AfM1) in whole milk powders, homogeneity, short- and long-term stability tests of naturally contaminated milk powders have been performed. The homogeneity of two AfM1-contaminated milk powders was studied by taking samples at regular intervals of the filling sequences and analysing in triplicate for their AfM1 contents by liquid chromatography with fluorescence detection (LC-FLD) using random stratified sampling schemes. The homogeneity testing of an AfM1 'blank' milk powder material was performed by determining the nitrogen content because AfM1 levels were below the limit of detection of the most sensitive determination method. The short-term stability of AfM1-contaminated milk powders was evaluated at three different storage temperatures (4, 18 and 40 degrees C). After storage times of 0, 1, 2 and 4 weeks, samples were investigated using LC-FLD. The long-term stability study comprised of measurements after 0, 6, 12 and 18 months after storage at -20 and 4 degrees C. Analyses were done by LC-FLD. Based on the homogeneity tests, the materials were sufficiently homogenous to serve as certified reference materials. Corresponding uncertainty contributions of 0.23-0.89% were calculated for the homogeneity. The stability measurements showed no significant trends for both short- and long-term stability studies. The long-term stability uncertainties of the AfM1-contaminated milk powders were 7.4 and 6.3%, respectively, for a shelf-life of 6 years and storage at -20 degrees C. Supplementary stability monitoring schemes over a long period of several years are currently ongoing.

Determination of trichothecenes in duplicate diets of young children by capillary gas chromatography with mass spectrometric detection

Trichothecenes are mycotoxins produced by several fungal genera, mainly Fusarium species, that can contaminate a wide range of cereals used for human and animal consumption. They are associated with various adverse health effects in animals and humans such as feed refusal, vomiting and immunotoxic effects. A method based on capillary gas chromatography with mass spectrometric detection was developed and validated in-house for the determination of nine trichothecenes in duplicate diets of young children. The trichothecenes were extracted from the sample matrix by water/ethanol (90/10). The extracts were cleaned by means of ChemElut and Mycosep columns. The cleaned extracts were evaporated to dryness and derivatized to trimethylsilyl ethers at room temperature. The residues were dissolved in iso-octane and washed with water. The final extracts were analysed for trichothecenes by GC-MS. The response was linear in the range tested (1-10 microg kg(-1)). Recoveries for the trichothecenes were between 70 and 111%, with the exception of nivalenol, which had a low recovery (34%). The limit of quantification for all trichothecenes was below 0.4 microg kg(-1). Seventy-four food samples from young children collected by 74 respondents in a duplicate diet study were analysed for trichothecenes with the developed method. The mean levels of deoxynivalenol, nivalenol, HT-2 toxin and T-2 toxin were 5.8, 0.3, 0.3 and 0.1 microg kg(-1), respectively. Based on the individual results, dietary intake calculations were made. For deoxynivalenol, the tolerable daily intake of 1 microg kg(-1) body weight was exceeded by nine respondents. For the combined intake of T-2 and HT-2 toxin, the temporary tolerable daily intake of 0.06 microg kg(-1) body weight was exceeded by nine respondents.

The development of five animal feed reference materials, certified for their aflatoxin B1 content

The development of three peanut meal and two compound feed reference materials and the certification of their aflatoxin B1 content is described. The materials were prepared and certified within the Measurements and Testing Programme of the Commission of the European Communities as part of a broad activity to improve accuracy and agreement of results of measurements on food and agriculture. RM 262 (peanut meal) was prepared from uncontaminated peanut products. RM 263 and RM 264 (peanut meals) were prepared from naturally contaminated peanuts which were blended with uncontaminated ones, to achieve the desired aflatoxin B1 mass fractions. RM 375 and RM 376 (compound feeds) were made by blending decontaminated dairy feed together with commercial feed ration and contaminated dairy feed with several feed compounds, respectively. Details are given of the preparation and the investigations to verify homogeneity and stability of the materials. The certification exercise was carried out by 17 laboratories using a variety of extraction and clean-up procedures. Most laboratories used liquid chromatography as the determinative step, although operating under a variety of chromatographic conditions. A few laboratories applied thin layer chromatography with densitometric quantification. Peanut meal RM 262 was certified as containing aflatoxin B1 at a mass fraction of < 3 micrograms/kg, RM 263 at 43.3 +/- 2.1 micrograms/kg and RM 264 at 204 +/- 10 micrograms/kg. Compound feed RM 375 was certified as containing aflatoxin B1 at a mass fraction of < 1 micrograms/kg and RM 376 at 9.2 +/- 0.5 micrograms/kg. The materials can be employed either to establish or confirm a calibration curve, or to check the performance of a method.

Rationale for regulatory programmes for mycotoxins in human foods and animal feeds

Currently, more than 50 countries have enacted or proposed regulations for mycotoxins in food and feed. There are various factors that may influence the establishment of tolerances for certain mycotoxins, such as the availability of toxicological data, the availability of data on dietary exposure, the distribution of mycotoxins over commodities, legislation of other countries with which trade contacts exist, and the availability of methods of analysis. In practice, only few countries have formally presented the rationale for the need to regulate, or for the selection of a particular maximum tolerated level, as a recent international enquiry demonstrated. Most of the limits for aflatoxins in food were based on rather vague statements of the carcinogenic risk for humans. There was a general consensus that exposure to a potential human carcinogen that could not be totally avoided should be limited to the lowest practical level. Several countries made a claim to a hazard evaluation (Belgium, Canada, India, The Netherlands, Switzerland, South Africa, United Kingdom, United States), although specifics were rather scarce. No rationales for setting limits for other mycotoxins were provided, except for Canada, where risk assessment was done for deoxynivalenol, zearalenone and ochratoxin A. It is apparent that in most countries either the scientific basis for regulation of mycotoxins is non-existent, or the science has not been fully utilized.

Rationales for the establishment of limits and regulations for mycotoxins

Although 50 countries have enacted or proposed regulations for control of alfatoxins in food or feed, and 15 of these countries also have regulations for permitted levels of contamination by other mycotoxins, very few countries have formally presented the rationale for the need to regulate, or for the selection of a particular maximum tolerated level. After several successive inquiries, information concerning the rationale for regulation was obtained from 21 countries. Most of the responses concerned limits for aflatoxin in food, and most of these were based on a vague, unsupported statement of the carcinogenic risk for humans. There was a general consensus that exposure to a potential human carcinogen that could not be totally avoided should be limited to the lowest practical level; the definition of practicality depended on whether the country was an importer or producer of the potentially contaminated commodity. A claim to a hazard evaluation was made by six countries (Canada, Belgium, India, United Kingdom, United States, Switzerland) without providing specifics; and one country, South Africa, referred to a risk determination. The most comprehensive rationale for any mycotoxin regulation was provided by the United States in support of limits for aflatoxin in specific animal feedstuffs. The responses provided no rationale for setting limits for other mycotoxins; but scholarly risk assessments for zearalenone and ochratoxin A have been published by Canadian government scientists, and a symposium presentation provides the information that in Norway patulin is regulated for quality control purposes only. It is apparent that, in most countries, either the scientific basis for regulation of mycotoxins is nonexistent, or the science has not been fully utilized.(ABSTRACT TRUNCATED AT 250 WORDS)

EC-collaborative study on the determination of aflatoxin B1 in animal feeding stuffs

A collaborative study was conducted to test a method, proposed in the European Community (EC) as a candidate-official method for the determination of aflatoxin B1 in compounded feeding stuffs. The study was undertaken on behalf of the European Commission's Community Bureau of Reference (BCR). It involved 25 laboratories from 11 EC countries. The method, based on chloroform extraction and Sep-Pak Florisil and C18 cartridge clean-up, offered either reverse-phase high performance liquid chromatography (HPLC) with iodine post-column derivatization, or two-dimensional thin-layer chromatography (TLC) as determinative steps. In the study, 22 laboratories applied HPLC, three laboratories applied TLC. The study involved six unknown samples. These consisted of blind duplicate samples of compounded feeding stuff, with target concentrations of aflatoxin B1 at less than 2, 8 and and 14 micrograms/kg. Statistical analysis of the HPLC data was carried out according to ISO 5725. For the less than 2 micrograms/kg sample, all reported aflatoxin concentrations were less than 2 micrograms/kg. At the 8 and 14 micrograms/kg level (pooled), repeatability (r) and reproducibility (R), expressed as ratios, were 1.4 and 1.7 respectively, and within-laboratory and between-laboratory coefficients of variation were 11% and 18% respectively. The study revealed that admittance of daylight in the laboratory caused losses of aflatoxin B1 and must be avoided. New glassware coming into contact with aqueous solutions containing aflatoxin B1 was found to be a potential cause of loss of aflatoxin B1. The method has been recommended to the European Commission to be considered for adoption in EC regulations.

Two-dimensional chromatographic method for determination of aflatoxins in liver; occurrence of aflatoxins in animal liver

A thin-layer chromatographic method is described for the analysis of aflatoxins in animal liver. Liver samples are extracted with chloroform and phosphoric acid. After filtration, an aliquot is evaporated and defatted by liquid-liquid partitioning. The extract is submitted to silica gel minicolumn cleanup and the final extract is concentrated and submitted to two-dimensional thin-layer chromatography (TLC). The identity of aflatoxins B1 and M1 is confirmed with trifluoroacetic acid (TFA) carried out on the thin-layer plate used for quantitation of these aflatoxins. The method permits the detection and confirmation of aflatoxins in liver in concentrations as low as 0.05 micrograms/kg. Average recoveries for aflatoxin M1 and aflatoxin B1 at spiking levels of 0.2 micrograms/kg were found to be 65% and 85%, respectively. With this method, 73 samples of bovine liver, 70 samples of porcine liver, and 56 samples of chicken liver taken from different slaughterhouses were investigated. In one sample of bovine liver, aflatoxins B1, B2, and M1 could be detected in concentrations of 0.10, 0.03, and 0.08 micrograms/kg, respectively.

Aflatoxin B1 in compound-feed reference materials: an intercomparison of methods

The BCR has undertaken a project to prepare compound-feed reference materials to provide a basis for analytical quality control for this assay. The first phase of the project, an intercomparison of methods for aflatoxin B1 in compounded feedstuffs at a level of ca 15 micrograms/kg is now described. The study involved 24 European laboratories who analysed two pairs of compounded feedstuffs. Each pair of feeds consisted of a contaminated and an almost uncontaminated sample (a near-blank) of otherwise identical composition. The feed pairs differed essentially only in their citrus-pulp and barley contents. The participants used a variety of methods of analysis, including chloroform, methanol-water and acetonitrile-water for extraction, TLC, reversed phase disposable cartridges and immunoaffinity columns for extract clean-up and TLC, HPLC and ELISA in the determinative step. Several performance characteristics were checked and the aflatoxin B1 contents were determined. Recoveries were found to range from approximately 70 to 110%. Coefficients of variation calculated from all the results obtained with the two pairs of contaminated samples were 16 and 19%. The study showed that, when properly applied, a number of methods employing variations in extraction, clean-up and end-method gave results which were in close agreement. It is concluded that there exists a sound basis for the establishment of reference values for the aflatoxin B1 content of compound feed reference materials which have been prepared in this project.

Aflatoxin B1 in peanut meal reference materials: intercomparisons of methods

The Community Bureau of Reference (BCR) is preparing a series of animal feed reference materials to provide a basis for analytical quality assurance for aflatoxin B1 analysis, a problem of particular importance in view of Community legislation. Before reference values can be assigned to the reference materials the major errors in the underlying measurements must be identified and reduced. This paper presents the results of two intercomparison exercises involving some 20 European laboratories who applied a wide variety of analytical methods. It is shown that the major source of error and discrepancy is connected with incomplete extraction and/or losses during clean-up and that, provided correction for recovery/background interference is made, many methods can achieve acceptable accuracy. Sources of error and their control are discussed, and essential details of the methods used are presented. It is concluded that analytical QA is more important than the use of standardized methods when a high degree of accuracy and comparability are required.

Current situation on regulations for mycotoxins. Overview of tolerances and status of standard methods of sampling and analysis

A worldwide enquiry was undertaken in 1986-1987 to obtain up-to-date information about mycotoxin legislation in as many countries of the world as possible. Together with some additional data collected in 1981, information is now available about planned, proposed, existing or absence of legislation in 66 countries. Details about tolerances, legal bases, responsible authorities, prescribed methods of sampling and analysis and disposition of commodities containing inadmissible amounts of mycotoxins, are given. The information concerns aflatoxins in foodstuffs, aflatoxin M1 in dairy products, aflatoxins in animal feedstuffs, and other mycotoxins in food- and feedstuffs. In comparison with the situation in 1981, limits and regulations for mycotoxins have been expanded in 1987 with more countries having legislation (proposed or passed) on the subject, more products, and more mycotoxins covered by this legislation. The differences between tolerances in the various countries are sometimes quite large, which makes harmonization of mycotoxin regulations highly desirable.

Comparison of six methods of analysis for the determination of aflatoxin B1 in feeding stuffs containing citrus pulp

Six published methods of analysis for the determination of aflatoxin B1 have been compared for their suitability to determine aflatoxin B1 in feeding stuffs containing citrus pulp. These methods are the official European Community (EC) procedure, four procedures proposed in the European Community to replace this method and a new procedure developed by the authors of this article. In all procedures chloroform is used for initial extraction. Various clean-up systems are then applied. For the ultimate separation and detection, use is made of high performance liquid chromatography (HPLC) in three procedures and two-dimensional thin layer chromatography (TLC) in two procedures. One method allows either HPLC or TLC. All experiments were carried out with samples of a batch of feeding stuff containing citrus pulp, artificially contaminated with aflatoxins B1, B2, G1 and G2 at levels of ca 13, 5, 10 and 4 micrograms/kg respectively. Three methods were found to be suitable: a procedure in which gel permeation clean-up and two-dimensional TLC are used; a procedure in which TLC clean-up and reverse phase HPLC with postcolumn derivatization are used: a procedure in which cartridge clean-up and either HPLC or TLC are used. The latter method is preferred because its efficient clean-up yields a very clean extract, allowing the application of various systems of HPLC or TLC. Published recovery data of these three methods for aflatoxin B1 vary from 85-90% at a level of ca 10 micrograms/kg feeding stuff.

Limitations in protection afforded by gloves in laboratory handling of aflatoxins

The permeability of latex and vinyl laboratory gloves by aflatoxins in chloroform or dimethyl sulfoxide (DMSO) has been investigated. Latex gloves provide good protection against permeation by aflatoxins in DMSO, but aflatoxins in chloroform permeate all types of laboratory gloves. If gloves are contaminated when aflatoxins in chloroform are handled, an immediate change of gloves is recommended.

Confirmatory test for aflatoxin M1 on a thin layer plate

The identity of aflatoxin M1 can easily be confirmed directly on a thin layer plate by reacting aflatoxin M1 with trifluoroacetic acid (TFA). This confirmation reaction is carried out on the thin layer plate which has been developed in 2 dimensions and used for the quantitation of aflatoxin M1 in the sample. TFA is superimposed on the separated M1 spot. The plate is kept in the dark 3 min, heated to 75 degrees C for 5 min, and developed with chloroform-methanol-acetic acid-water (92 + 8 + 2 + 0.8). The Rf value of the blue-fluorescent derivative is compared with that for the M1 standard. The method was used successfully on extracts of milk, cheese, and liver. M1 quantities on the plate as low as 0.5 ng can be confirmed by this method. The method is also suitable for simultaneous confirmation of aflatoxin B1.