A good friend of mine 's lab ingested a corn cob. He raided the trash, and she didn't even know the dog had eaten it. When the lab started to get sick, she took him to the vet (the dog had previously had surgery after swallowing wood- darn beaver) and the vet did blood work, but nothing else. During the weekend, lab got more and more sick, finally ending up in doggie ER. After x-rays and exploratory surgery, the vet produced a 4 inch corn cob. If she had waited much longer, the dog would have been in some serious trouble. Retrievers are the catfish/pigeons of the dog community- they eat anything.