Just weeks before the farm's dairy is due to start opeation, 50 farmers from all over France arrived at the site, intending to dismantle the giant milking machine, designed to milk 1,000 cows three times a day.
Public prosecutor Bernard Farret said that five activists, including the spokesperson of the Confédération Paysanne union, Laurent Pinatel, were held in custody on theft and vandalism charges.
According to the union, the "factory farm" is a symbol of industrial agriculture which is killing small farmers' livelihoods.
The protest received support from Green party, EELV.
"This factory farm goes against animal welfare, the environment and sustainable development," in the region, a party statement said.
Construction magnate Michel Ramery plans to open the farm this spring.
The farm will house 1,750 cows in one 234-metre barn.