Unfortunately there is not much you can do about this problem.
I have talked to a few Vets about this too and they agreed that most of the time it is not related to nutrition, unless the animal is locked in a cage or kennel and has nothing else to eat.
Most of the time it is a bad habit...they develop a taste for it and the habit begins.
I have dogs that will not eat their own feces but will try to eat the feces of my other dogs.
In my dogs' case...they were both pet shop dogs(yes, I know buying pet shop dogs is terrible, my son bought one and my hubby bought one...there is no going back now) But in any case...they were in the pet shop kennels and played with and ate their kennel mates(and maybe their own poop)for fun.