> Obviously they are needing some mineral
Not nescessarily Ann,
There are
many reasons and as your saying that its your dogs (plural) and that its only sometimes.. I'd be more inclined to think it
wasn't any defficiency or malabsorbtion. If your feeding a commercial dog food then the balance should be
adequate (or better..dependant on what is fed and how your dogs uptake)
Soil can be a tempting forage for dogs because of the plant matter and even old feacal matter (cats,foxes etc) Some fertilizers contain organic matter which smells gooood (read gross for us!) and of course there could even be rotting corpse of mouse etc in there. :)
(I found a flat old leathery petrified toad in an area of my garden that my Sibe was regularly chomping on!)
*If *you have been 'tinkering' with diet and think there maybe a gap somewhere and this is leading you to wonder about Mineral defficiency.. then we'd really need to know what you've been feeding (and amount) to what (size/sex/age/sedentary v working dog) and what soil is being favoured? for example clay soil is tempting for iron content but mainly for salt (and the salt can be more from a tasty need than the dogs own diagnosis of dietary need)
HTH?