Cattle breeders have begun an indefinite blockade of Spanish slaughterhouses to protest about effects of the mad cow disease crisis.
The action could leave the country without meat stocks within days. Spain normally slaughters up to 7,000 cows per day.
The protest was called by the country's three main breeder associations and is backed by two farming unions.
The protesters are calling on the Government to introduce measures to alleviate the problems caused by BSE.
Javier Lopez, president of breeding group Asovac, says it is being supported by a majority of the country's 200,000 cattle farmers.
He said: "We're doing this out of despair. Our aim is not to leave people without meat but that may end up being the case".
The protest is set to continue until the Government agrees to help farmers.
The breeders accuse Prime Minister Jose Maria Aznar's Government of turning a blind eye to the crisis and demand compensation for the loss in sales. They are also pressing for the Government to pay for the slaughter and disposal of suspect animals and to fund a campaign aimed at restoring confidence in the sector.
At Madrid's main slaughterhouse, some 25 protesters, watched by nearly 50 riot police, set up a picket line. Traffic in and out of the abattoir has been scant.
The breeder associations, Asovac, Aprovac and Arabovis, estimate that in a matter of months the mad cow crisis has reduced meat consumption by 70% and caused financial losses to the sector of 11 billion pesetas ($65 million).
Since October there have been five confirmed cases of bovine spongiform encephalopathy, mad cow disease, in Spain.