Contrary to the popular belief, wolves do not eat the contents of the large 
prey's stomachs.  And dogs are subspecies of wolves. 

According to Dr. David Mech who spent several decades studying wolves and is 
world authority on them, they open the stomach, shake the contents out and eat 
just the stomach itself.  I read all the books by Dr. Mech and he gave several 
accounts how they eat their prey. I don't know where that notion of eating the 
stomach contents came from but certainly not from Dr. Mech.  Wolves also do not 
eat small rodents unless starving, but that would be the only instance that 
they would eat a stomach contents.  

Barbara


  The page at http://dogsobediencetraining.com/info/learn_dog_wiki.htm 
  makes a good point.  Although canines are carnivores, in the wild they 
  get a good bit of vegetable matter because they would eat the contents 
  of the stomach of their prey. If fed only meat, then they are not 
  getting this which would normally been a natural part of their diet.  
  Thus to duplicate what they would have gotten in the wild, they should 
  also be fed prechewed vegetable matter which is similar to what their 
  prey would have normally eaten.

  Marshall