I have an Italian greyhound 8 months old he has all his shots and monthly heart worm and flea tick treatments. My question is: Every time I take him out for a walk or to the dog park(where shots and vaccines are required) he tries to eat leaves, grass, dirt, etc. Should I stop him every time he tries to eat one of these things? If so I would have to spend almost the whole time saying "No" & pulling him away from things. This is my first dog and i'm still learning and just curious. Thanks!