eating rocks

Question
My lab now 5 years old keeps eating rocks, fortunately small enough to bring back up or pass. Two Vets and a Guide dog expert cannot give me an answer as to why. We have tried all kinds of supplements, training (He is a medical service dog) and speciality foods. Is this specific to the breed? I have had dogs and bred (another breed) for over 20 years and never heard of this behavior?  My concern is that it may become dangerous in the event he eats a rock too large to bring up or pass.  He only does this when left in the dog run with our two other dogs.  He is the middle dog in age. (The middle child syndrome-seriously?).  We have done everything to keep it rock free, however our topographical area prevents that. Do you have a recommendation? Thank you.

Answer
If anything, Goldens are worse about gulping down indigestible.  You are right to be concerned.  I have seen rocks in a display of objects surgically removed from dogs.  I am not sure what to do.  Start by limiting the time he spends in the dog run.  For relief, take him out on a leash in a grassy area.  Otherwise, keep him in the house.  When you aren't around, if you can't trust him loose in the house, crate him.  Other dogs may not be as bad as the young Labs I am plagued with.  Still your house and dog
will be much safer with the dog in a crate when you are away.  The dog may be
happier in its den than loose in the house.  It relaxes, it feels safe in its
den.  It rests, the body slows down reducing the need for water and relieving
its self.  Dogs that have been crated all along do very well.  Many of them
will rest in their crates even when the door is open.  I think the plastic
ones give the dog more of a safe, enclosed den feeling.  They are harder for
dogs to open too.    Metal ones can be put in a corner or covered with
something the dog can't pull in and chew.  Select a crate just big enough for the full grown dog to stretch out in.

Leave it some toys.  Perhaps a Kong filled with peanut butter.  Don't leave
anything in the crate the dog might chew up.  It will do fine without even any
bedding.  You will come home to a safe dog and a house you can enjoy.

A dog that has not been crated since it was little, make take some work.
Start out just putting its toys and treats in the crate.  Praise it for going
in.  If you have been able to trust it with any bedding, put that in the crate.
Feed it in the crate.  This is also an easy way to maintain order at feeding
time for more than one dog.

Use the crate only when you must  I have a short length of chain fastened to
my computer desk.  With more mats around the chair mat, this gives a place
where the puppy is with me, but about as controlled as in the crate, while
still allowing me to get some work done, or at least answer All Experts questions.

If you do leave him in the dog run, try to eliminate all the rocks about an inch or 2 in diameter.  The smaller ones shouldn't hurt, and he shouldn't able to swallow the larger ones.  If nothing else, excavate the dog run, put down landscape fabric and then pea gravel.