Dog throwing up clear, lethargic after eating deer. What's wrong?

Unfortunately vomiting right after eating or drinking is often a sign of a foreign body obstruction. It is possible that Gunter ate a piece of a bone/rib etc. that has become lodged in his gastrointestinal tract. As this can be a life threatening condition, it is recommended to have him examined by a veterinarian and to have abdominal x-rays taken ASAP. Unfortunately, if X-rays do show a foreign body obstruction, surgical removal is usually the only solution. If no foreign body obstruction is noted on x-rays, your vet may give Gunter an injection of an anti-nausea medication called cerenia, give him SQ fluids for hydration (and which will help if he has pancreatitis from eating the deer or table food), as well as start him on either a prescription intestinal diet or recommend boiled rice and chicken for the next 3 days. Good luck!