Why does my 6 month old mastiff eat rocks? He has no other problems with eating and is healthy. I try to watch him but he finds them when I am not looking, and I see them in his stool. Could they harm him?

What kind of plant can hurt my puppy?

My dog is 5 months old and every time we go for walks he tries to eat everything he sees. Just yesterday he ate something and it's in his throat. He isn't choking on it but I know it bothers him because he is coughing trying to get it out. What can we do to make whatever it is go down?