I have a 17 week old miniature dachshund. He has always seemed to like to eat a little bit of grass since we got him. Yesterday he threw up what looked like greenish bile but was acting fine apart from being sleepy most of the day because of the heat. This morning I gave him his breakfast and he ate it all. About 5 hours after eating his breakfast he threw it up and it had blades of grass in it. He did was to eat more grass just before he threw up. Why could this be?