Lantmannen highlighted the severity of the European Union's opposition to genetically modified foods by revealing that it had closed down feed production capacity after the discovery of biotech rapeseed meal.
The Swedish agriculture and food co-operative said that it was taking action against the, unnamed, supplier of the rapeseed meal, after routine internal tests discovered "traces" of genetically modified material.
"The raw material comes from a reputable supplier that guarantees GM-free product," Lantmannen said.
The co-operative has closed down the affected operations for cleansing, and contacted customers which took deliveries from the Västerås plant, where the biotech-tainted fed is believed to have been produced between June 22 to July 3.
'Obviously very regrettable'
The contamination was termed "obviously very regrettable" by Stefan Atterwall, the head of Lantmännen Agriculture's fodder division, said, with the group adding that it was to introduce extra controls at its Västerås plant in an effort to avoid a repeat tainting.
And it issued a reminder of the extent of anti-GM restrictions in the European Union, in contrast with many major growing countries, such as in the Americas, where biotech crops are commonplace in feed.
Sweden one of the more relaxed countries towards GM crops, having hosted - marginal – plantings of amflora, a genetically modified potato for use making industrial starch, and which, with a Monsanto corn variety, is one of only two crops cleared by Brussels for cultivation.
France, the top EU corn grower, has banned the Monsanto corn despite the seed's EU backing.
While no biotech rapeseed is grown in the EU, it is produced in major exporting countries Canada and Australia.