23 May 1991,
The Biscayan farmers tried to introduce cows at the headquarters of the Civil Government of Bizkaia. It was a protest against the low prices they paid for milk and meat. The police began to erase and eventually threw rubber balls at people and animals. The other day, in San Sebastian and Pamplona, hundreds of litres of milk were thrown into the soil and meat fillets were distributed.
Source:
Sabino Ormazabal, 500 acts without violence, another way to tell the story.