I'm not sure what good salt in the eyes would except burn like the dickens.
IF, it was debris, it may purge the eye of the debris. But i wouldnt do it to myself, so there aint no way id do it to my dog or livestock. On top of that, it might make the dog scared or resentfull of the owner, not being able to trust the hand that feeds them, makes it a battle of pissing in the wind.