I took her to the vet and the vet said she looked good, but that was just a general check up. Libby, my dog, would eat anything and everything even bugs and salads, but not anymore. Also, she still drinks the same amount of water. She's 8 years old now so she is considered a senior dog. She has no more energy and sleeps all day. Most her energy would be in the morning and night. I think she eats the horse poop because of what we give the horse. It's a garlic powder for both horses and dogs, it helps keep the flies away and helps with digestive system in some way. If she fills up on poop could that be why she has no energy? Its just abd grass. The vet said we don't want her to lose anymore weight. I'm thinking about having her blood tested, as that was an option given.

I would definitely rule out anything medical.

Horse poop is just grass and water. It's a major filler. It'd be like you eating a bunch of vegetables. Its full of fiber and very, very filling. Try and keep her away from the horses to see if her appetite will come back.

STOP the supplement. Garlic in amounts more than 'a bit' can cause hemolytic anemia due to the effects on the red blood cells. See the link below, and scroll down to the section on "garlic and onion toxicity".

http://www.vetinfo.com/dtoxin.html

Also, 8 years old... have her tested for low thyroid. She has been spayed, too, right? ( There are some problems if not, this isn't a solicitation to have it done. )