i recently had to have one of my puppies put down and i was wondering if anyone could help me find out what was wrong with the puppy. My bitch had 10 pups and they were all fine until they reached about 4 weeks wehn it became apparent that one of them was a lot smaller than the rest - a runt i think its called. i started feeding her seperately to make sure she didnt get pushed out of the food dish by the other bigger pups, but it didnt seem to make any difference. she seemed to get smaller and skinnier every day, despite the extra attention :-(
I also noticed that every time she ate she would go off into a corner afterwards and make really pitiful noises before being sick, this happened quite a few times so I took her to the vet and explained the situation and he advised me to have her put to sleep as she was very underweight and he said it was not the best idea to rear puppies with health problems. now I feel really bad, what do you think could have caused this and have any breeders seent his happen or know what causes it?
the other puppies are all fine and most have now gone to their new homes. It has put me off breeding again, I feel quite upset :-(

It's no more than a guess but I'd wonder about congenital megaoesophagus. Was the pup actually vomiting or was it regurgitating food? And what is the breed? Was the pup small from birth and did it gain weight normally while still on mum? If it was always small and didn't put on weight normally when on mum, chances are that it something else entirely or maybe the pup had some other abnormality. Unfortunately it's now too late to have an autopsy done on the pup and that is the only sure way to make a diagnosis that would be useful in deciding whether or not to mate this bitch / her progeny again. If it was megaoesophagus I know of one puppy with a mild case that was successfully reared by experienced breeders who will keep her lifelong but in most cases I reckon your vet was probably right for the right reasons.