My dogs always liked to chew on sticks, actually they would haul large branches in the yard & chew on them. I found those ropes with knots on both ends that you can buy at the pet stores work pretty good for chewing on. It looks like by the pictures you have Australian Shepherds? I have a 14 year old Australian Shepherd & he use to pick up big branches & run along with them & expected me to play tug of war with him. The other dog an Australian Cattle Dog would grab onto the branch & they would play tug of war also. My sons dog had a long nylon rope he likes to tug around the yard & when he was a pup he was tugging on the rope & one of his baby teeth fell out.