The company had announced the closure of a plant last week, in a cost- cutting move that will involve 140 job losses. But the Spillers group had bargained without the strong-arm tactics of the French.
Daniel Boulet, the managing director of Spillers Petfood, France, and his human resources director, Bernard Manhaval, were "comfortably detained", as the company described it, at the factory throughout Monday night, before being allowed to leave in the morning.
The company says they were not tied up and were given food. It is therefore unlikely that the management duo had to resort to opening a couple of tins of Felix to ease their hunger pangs.
"I think they spent the night sleeping in their chairs and were allowed home in the morning to change their shirts and have a shave," a spokesman for the company said. "They then came back to resume negotiations."
The company added: "We want to come to an amicable arrangement and hope to resume discussions with the Workers Council. But the plant will close."
The local trade unions want the local prefect to appoint a mediator to resolve the conflict at the company.
The striking staff want the closure plan to be withdrawn and demand that Dalgety either modernises the plant or builds a new plant there.
The closure is part of the rationalisation programme that followed Dalgety's acquisition of Quaker's pet food interests in Europe last year.