For the not eating, it is a common enough problem it has a section in the sticky at https://www.askmehelpdesk.com/dogs/i...tml#post254171
Post back with any questions it leaves.
I am not sure I can help much with grass eating. It is so common with some dogs that I no longer accept the conventional wisdom that they do it because their stomach is bothering them as a purgative. There may be cases of that. However, if that was true, I would have to accept my Aster's stomach constantly bothers her, because she seldom misses a chance to eat long, coarse grass. I seldom see her eating the fine, short grass in the backyard at home. Yes, they frequently throw up after eating grass, but they also frequently throw up after eating other things they find. I think it is like the binge drinkers that drink because they like being drunk, and throw up. There is another thread now about this, https://www.askmehelpdesk.com/dogs/d...-94347.html
I have been thinking some more about this. Much of my personal experience has been with the always famished, eat anything young Labs. Yes they eat grass, and sticks, leaves, feces, acorns, plastic, twistems, the handles on my tools, electric cords, socks, the list is endless. And frequently hack stuff back up. Aster is 13 and still eats that way, although no longer a problem chewer. I am trying to remember if the one Shepherd I had, and the one Lab that ate like a Shepherd were as bad about eating grass as many of my other puppies. If your Pit Bull eats grass, but not its chow, perhaps it is seeing grass as tasty variety. When I watch my Aster eat grass, she looks like she is enjoying it, not that her stomach is bothering her.
If he waits until he comes back inside to puke, you might try to limit his access to grass, although if he is eating the grass in the yard, that would be tough. Again, in the sticky near the end of the housebreaking section, I have some help on cleaning up messes. Aster seldom pukes after her grazing. We went to the woods Sunday afternoon as we often do, and she enjoyed her grass. In the morning, there was enough processed grass I had to wash the cover to her bed, plus clean up some more from the hardwood floor.
This is something I posted to another site last year:
My Brown Swiss
For years the only dog we had in the house was the puppy we were raising for the dog guide school. They are NEVER allowed to be off lead except in a fenced area. That is explicitly stated in the body of the contract. After Aster retired as a dog guide a couple of year ago, I was free to do as I wish with her. My rules mainly are she enjoys it, and it doesn't hurt her. I also do not abuse people's trust and slip her in places her current status as a pet doesn't allow. She stays on lead on our daily walks that never get more than a 1/4 mile from a road. However, Sunday afternoons we drive out to the state land around the reservoirs. She has a good run off lead and often a swim. I have restricted her swimming since she got pneumonia after a swim in November.
Today, almost as soon as I pulled the slip collar off, she started grazing. It was almost as though she missed the grass all winter, and now it was greening up for the spring, and much longer than our yard at home, she was enjoying it. I see many suggestions of why dogs eat grass. I think in some cases, they select a coarse grass to make themselves throw up if their stomach is bothering. Or maybe they never learn it upsets their stomach. Many other times, they just seem to eat it. Some times they seem to sniff around and only eat very carefully selected grass. I have wondered since they often eat feces, if they are are finding contaminated grass to eat.