The pig auction in the Breton town of Plérin started after midday on Tuesday with a lowest possible sale price set at 1.37 euros a kilo.
It usually opens on Mondays and Thursdays but farmers were desperate to clear a backlog of 5,000 animals they have not been able to sell because of the crisis.
A further 12,000 pigs were newly up for sale.
But neither the Cooperl cooperative nor the Bigard company, who between them buy 30 per cent of the animals on sale, were present to make bids.
That raised fears that the pigs would sell at below the government's target price of 1.40 euros a kilo, the level farmers say they need to make ends meet.
Although only 15 per cent of France's pigs are sold in Brittany, the market at Plérin sets prices nationwide.
Cooperl and Bigard, who slaughter and sell on the meat, also boycotted Le Foll's roundtable, leaving farmers and the market's management alone with the minister.
They are to meet Le Foll separately on Tuesday and Wednesday.
They want a return to "market prices", claiming that French prices are 28 centimes higher than those in Germany and 38 centimes higher than those in the Netherlands.
Le Foll is to meet represatives of Spain, Italy, Portugal in Madrid next week and of Germany and Poland on 31 August to try to stop French farmers being undercut by other EU producers and discuss the effects of the embargo on Russia.
A special European Council will discuss the crisis on 7 September and French farmers have promised to demonstrate outside it.
A small group of France's picketed a distribution centre for the Lidl supermarket chain in the north of France on Tuesday, claiming that most of its milk and meat was improted from Germany and other European countries.