What makes dogs want to eat grass and horse poop ? Mine are crazed to get out and eat green grass and horse poop. I have concerns that it might be worms or that they will get worms from this activity.

Don't worry about dogs eating grass...helps them get rid of gas or sour stomach...now horse poop...don't encourage them to eat it...there's little nutrition left in the grass there and the chance for parasites are much greater

Are they young? I have one that was crazy for cat poop, and our neighbors collected feral cats...Lucky he grew out of it.

My pup was the same way when it came to eating poop. Grass is perfectly fine, but stay away from the poop eating in general haha, but especially as a pup. You don't want him contracting parvo at an early age.

Puppies; just about everything goes in their mouth; they usually grow out of that stage.

maybe hes a vegan

He called the [censored] poop

Mine are like cows grazing when they come across the certain types of grass. If I tell them Leave It, they move along.
When it comes to poo I say nothing, but nick them with the ecollar.
I haven't caught them trying to eat any in a while.

One of the guys on the "Red Neck tour" (they call me tater) said his dog ate every pile he found, kept the yard spotless. Neighbors wanted to borrow the dog to clean up their yards. He declined, said the dog wouldn't be hungry when it got back to his house and he'd have to start scooping again.

My lab was crazy for cat poop... he'd even go digging it out of the cat boxes...

Supposedly (from 'experts'), cat poop is a delicacy to dogs and it's quite common for all kinds of dogs to eat it...

Here's some links from my previous researching the topic:
Eating Cat Feces from Cat Boxes
Coprophagia (ASPCA)

-z

Mine are not young and I think I will use the shocker on them

Don't sweat it, just let them sleep outside and have fresh water. I feed raw on occasion with no issue. My dogs love to get in the chicken coop as well. I just water and feed normally. Now smoked pork leftovers are a mess. lOL