I was hoping to get some responses back but want you to have as much of an answer as I can give with the information you supplied. First let me give you some information about Coprophagia which is eating feces. Many dogs eat their own feces. Some eat any feces they find. Cat feces seem to be a favorite. No cause has been determined as to why dogs do this though some believe it may be a dietary deficiency while others believe it to be an obsessive compulsion disorder. If you are not feeding your dog a high quality dog food, you may wish to try switching foods. Some believe that if a dog is experiencing mal absorption problems the stool will smell like food and thus the dog eats it thinking it is food. Additionally, some dogs learn this behavior from their moms since they keep the den clean. As parasites are contracted frequently through feces, your dog should be tested for parasites. Blood tests can be run to rule out a medical cause. Shepherds can have problems with pancreatic function that can lead to diarrhea and food passing through the system too quickly and thus would smell more like food than if his system was working more normally. The best thing to do is try and curb your dog's tendency to do it.
Number one thing to do is to get the temptation out of the picture by removing feces out of the yard as soon as possible and keep it cleaned up. You can also put hot sauce or other pepper product on them so the dog finds then terrible tasting. There are over the counter products that you can give your dog daily to prevent this condition. They work in some cases and if it works for you, then it’s an easy solution. You can buy them at most pet stores. :
It will be harder to treat if your dog eats it’s own feces right after going. You will need to be with your dog when it is going and divert your dog away from it, praising your dog when it does not try and eat it. A firm “leave it” and correction should be said when he tries to eat it and comes in handy in the future for other items you do not want your dog eating.
You can read more about Coprophagia here.
For his biting you and your wife, you need to obedience train him. If he is biting you and not to the point where you have gotten rid of him, it is likely him reprimanding you because he thinks he is the boss or if he is an older dog, he may be getting senile.
I think it is likely a younger dog so obedience train him so he sees you and your wife who has to help as the bosses. You don't reprimand the boss. The boss (humans) do the reprimanding via the word NO. Don't ever hit him as that will encourage physical reprimands and his physical reprimand will be bites. So keep them verbal reprimands.
The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
This usually is enough to stop a dog from reprimanding their owners. Now if he is mouthing your hand, instead of taking it out of his mouth, move it further in and he will likely gag and find it unpleasant. If you keep doing it, he'll stop trying to control you with the behavior.
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Since there have been recalls on certain foods, please check the following site to be sure the food your animals eat is not affected. If it is affected, contact your vet as soon as possible. Have your dog seen if they have any symptoms.