The transport trailer carrying about 35 cattle crashed on its way to Ontario.
One lane of Highway 20 westbound remains closed.
Radio-Canada is reporting that it appears the driver fell asleep at the wheel.
About a dozen of the cattle were thrown from the trailer and police said six of them are expected to survive.
Officers had to shoot six of the escaped cattle in order to prevent danger to motorists.
Police said the remaining cattle inside the truck will be euthanized by a veterinarian.