Occurrence of mycotoxins in feedstuffs of dairy cows and estimation of total dietary intakes.

A survey was conducted to determine the occurrence of mycotoxins in feedstuffs of dairy cows in the Netherlands and to estimate total dietary intakes of these compounds. Twenty-four dairy farms were visited twice and samples taken of all diet ingredients. Feed intake data were collected by means of questionnaires. A total of 169 feed samples were collected and analyzed for 20 mycotoxins using a liquid chromatography tandem mass spectrometry multimethod. Silage and compound feed were the main diet ingredients, representing on average 67 and 23% of dry matter intake, respectively. Deoxynivalenol (DON), zearalenone, roquefortine C, and mycophenolic acid were the mycotoxins with the highest incidence. The incidence of DON in silage, compound feed, and feed commodity samples was 38 to 54%. The incidence of zearalenone in silage, compound feed, and feed commodity samples was 17 to 38%. The DON and zearalenone had a low incidence in forage samples and were not detected in ensiled by-product samples. Roquefortine C and mycophenolic acid were only detected in silage and ensiled by-product samples (incidence 7 to 19%). Fumonisins B(1) and B(2) were detected in 2 compound feed samples and one feed commodity sample. Aflatoxins B(1), B(2), G(1), and G(2), ochratoxin A, T-2 and HT-2 toxin, 3-acetyl-DON, 15-acetyl-DON, diacetoxyscirpenol, sterigmatocystin, fusarenon-X, ergotamine, and penicillinic acid were not detected in any of the samples. Average concentrations of DON, zearalenone, roquefortine C, and mycophenolic acid in complete diets were 273, 28, 114, and 54 microg/kg, respectively. Maximum concentrations were 969, 203, 2,211, and 1,840 microg/kg, respectively. Calculated average daily intakes of these mycotoxins were 5.0, 0.5, 2.0, and 0.9 mg/animal, respectively, and maximum daily intakes 19.3, 3.5, 38.9, and 32.3 mg/animal, respectively. Corn silage was the major source of all 4 of these mycotoxins in the diet. Extremely high concentrations of roquefortine C and mycophenolic acid (up to 45 and 25 mg/kg, respectively) were detected in visibly molded areas in surface layers of corn silage. These areas appeared to be the main source of roquefortine C and mycophenolic acid in the diet. Because carry-over of DON, zearale-none, roquefortine C, and mycophenolic acid into milk is negligible, their occurrence in feedstuffs is not considered of significant concern with respect to the safety of dairy products for consumers. Potential implications for animal health are discussed.

Occurrence of mycotoxins in maize, grass and wheat silage for dairy cattle in the Netherlands.

The occurrence of mycotoxins in 140 maize silages, 120 grass silages and 30 wheat silages produced in the Netherlands between 2002 and 2004 was determined using a liquid chromatography coupled with tandem mass spectrometry detection (LC-MS/MS) multi-method. Deoxynivalenol (DON) was detected above the limit of quantification (LOQ) of 250 µg kg⁻¹ in 72% of maize and 10% of wheat silages. Average DON concentrations were 854 and 621 µg kg⁻¹, respectively, and maximum concentrations 3142 and 1165 µg kg⁻¹, respectively. Zearalenone was detected above the LOQ of 25 µg kg⁻¹ in 49% of maize and 6% of grass silages. Average zearalenone concentrations were 174 and 93 µg kg⁻¹, respectively, and maximum concentrations 943 and 308 µg kg⁻¹, respectively. The incidences and average concentrations of DON and zearalenone in maize silage were highest in 2004. The incidence of other mycotoxins was low: fumonisin B1 and 15-acetyl-DON were detected in 1.4 and 5% of maize silages, respectively, and roquefortin C in 0.8% of grass silages. None of the silages contained aflatoxins, ochratoxin A, T2-toxin, HT2-toxin, sterigmatocystin, diacetoxyscirpenol, fusarenon-X, ergotamine, penicillinic acid, or mycophenolic acid. This study demonstrates that maize silage is an important source of DON and zearalenone in the diet of dairy cattle. Since the carryover of these mycotoxins into milk is negligible, their occurrence in feed is not considered to be of significant concern with respect to the safety of dairy products for consumers. Potential implications for animal health are discussed.

Sample comminution for mycotoxin analysis: dry milling or slurry mixing?

A comparison was made between dry milling and slurry mixing as a comminuting step preceding mycotoxin analysis. Sample schemes of up to 30 kg are mandated by European Commission legislation. Cocoa, green coffee, almonds and pistachio samples of 10 kg were milled by a Romer analytical sampling mill and all three subsamples were analysed for aflatoxin B1 or ochratoxin A content. The homogenization process was evaluated in terms of the analytical results, coefficients of variation for different mills and particle size distributions. Coefficients of variation for the comminuting step were higher for dry milling than for slurry mixing. This difference was explained based on measured particle size distributions for both milling types. Measurements also showed slight differences in mycotoxin content of samples based on milling procedures. This might lead to lots being wrongly accepted or rejected based on an erroneous subsample result. It was concluded that sample comminution was best performed by slurry mixing, which produced smaller particles and, consequently, homogeneous samples with lowest coefficients of variation. Additional data are given on analytical results in 10-kg subsamples that originate from the aggregate 30-kg sample as described in Commission Directive 98/53/EC.

Evaluation of effect of measures taken after a DON outbreak.

In April 1999 an amount of 2600 µg/kg DON was found in a sample breakfast cereals in the Netherlands. This event was the start of a lot of activities, which dealt with the prevention, control, health and consumer aspects of DON in food for human consumption. The Food Inspection Services started a monitoring program to measure DON in cereal products, flour and raw cereals. The National Institute of Public Health and the Environment, another part of the Ministry of Health in the Netherlands, was asked to carry out a risk analysis on DON. This was the basis for the Minister of Health to set an action limit for consumer products. She also informed Brussels and asked for a European limit. The Main Board on Agriculture set out to implement measures to be taken at harvesting, milling and bread baking industry. The Scientific Committee on Food of the EC expressed an opinion on DON in December 1999. Worldwide attention leads to discussion of a DON limit by JECFA in February 2001.In the period may 1999 until march 2002 a number of more than 1700 samples were analysed on DON. These originated from the cereal harvest of the years 1998 until 2001. The results showed a sharp decrease of DON content in samples of harvest 1999 when compared to 1998. This lower level was maintained in the 2000 and 2001 harvests. Apparently the measures taken to control the DON level succeeded to maintain values below the action limits. Despite these activities a smaller outbreak of DON appeared in 2001 in pasta products at a lower extent. This indicated that control should be done systematically, not sporadically, and at a European level, which is made possible since EC has set a limit in July 2000. Analytical results of the measurements are presented, together with the chronological order of the associated activities of national, EU and worldwide bodies on human health control. Special attention is paid to DON in bread, related to the level in flour.

Determination of aflatoxin B1 in pistachio kernels and shells.

A method was developed for accurate measurement of aflatoxin B1 in the edible portion of pistachio nuts. Twenty-nine samples of kernels with and without their shells were slurried with a Mega Ultra Turrax. A subsample of the homogenate was extracted with water-methanol, defatted with petroleum ether, purified with a silica solid-phase extraction column, and redissolved in methanol. After separation on an octadecyl column and postcolumn reaction with on-line electrochemically generated bromine, the aflatoxin B1 derivative was detected fluorometrically. The shells contained less than 1% of the aflatoxin B1 found in the edible kernel, and they accounted for 41.7-46.8% of the weight of the whole pistachio. These observations indicate it is possible to analyze an entire sample, up to 25 kg, as a whole and still be able to judge whether it meets the legal tolerance limit of 5 micrograms aflatoxin B1/kg edible part, as set by the Dutch Food Act.