Why are my 4-week-old puppies sick with diarrhea and heavy breathing?

Poor pups! The most common cause of diarrhea in puppies this age is intestinal parasites, so I would recommend taking a fecal sample to your vet to be checked tomorrow morning, if you can. He/she can prescribe an appropriate dewormer or other medication if needed, depending on what is found. If the fecal exam is normal, then it would be best to bring the puppies in for an exam sooner than next Monday if possible since they may need an antibiotic or other medication to treat the diarrhea - it's best not to let this go too long, since young puppies like this can get very sick, very quickly.

It's possible the change in food could be causing digestive upset. The best way to start transitioning to solids is to make a slurry of their regular milk replacer that they've already been on combined with a little bit of the puppy food. This helps make it easier to digest without being too big of a change and may help settle their stomachs. Checking for any parasites with a fecal exam and deworming may also help, however if the vomiting or diarrhea continues, a vet checkup to rule out anything more serious is best.

Poor pups. While a heavy parasite load can cause severe GI upset, and anemia which can cause a pup to become extremely lethargic, have bloody diarrhea, etc, I would also want to rule out underlying illnesses as a possibility. It would be best to bring them to a vet ASAP especially if they are lethargic or unable to keep any food or water down as puppies can quickly become very dehydrated. They may also need supportive care such as an IV or injected medications if they are very ill from the parasites or other causes. You can try continuing to offer water, or rubbing a little honey on their gums for energy until you can get to the vet, however due to the severity of symptoms it would be best to seek emergency care.

It sounds like the smaller puppy may have ‘failure to thrive’. This is especially common with puppies from large litters and not surprising since the mother dog is refusing to feed them. It sounds like the bigger pup is doing great and you don’t need to worry about him at all. You should get a small scale (like a gram scale) so you can weigh the smaller pup everyday to ensure she is gaining weight. It is a little early but you could try to start introducing puppy food her as well. You can mix the canned food with milk replacer or moisten kibble with the milk replacer and see if she prefers this. If she is not eating much it makes sense that she is not pooping as frequently. Continue to stimulate her to defecate several times a day. You should also have the puppies dewormed at this age as well. If the puppy continues to refuse food after trying the above suggestions, you may need to take her to the vet to be examined. Your vet can also instruct you on how to safely syringe feed (or possibly tube feed) the puppy to ensure she is getting proper nutrition. I hope this helps. Thanks for using Petco Pet Education Center, formerly Petcoach. Best of luck!

Thanks for using Petco Pet Education Center, formerly Petcoach! Soft stools can be normal as they transition from formula to kibble or canned food. If she is otherwise doing well, this may be ok. If it ever becomes consistent diarrhea, have her evaluated by a veterinarian before her scheduled appointment. Keep in mind that it may be best to continue the formula until she is 6 weeks old. Best of luck!

Any food that says "puppy" should be just fine. You can continue to feed wet, or you can use dry. If she prefers moist food, you could even add a little water to the dry food. All puppies that aren't large breeds can use the normal puppy food. Large breeds need different mineral percentages for their extra large bones. I have fed all of my dogs Purina ProPlan since they were puppies. Here is a link: https://www.drsfostersmith.com/product/prod_display.cfm?pcatid=31180&cmpid=sc

Thanks for using Petco Pet Education Center, formerly Petcoach! Yes this is definitely possible and I would agree with you that this is the most likely reason for the diarrhea. I would recommend you go back to the previous diet and things are likely to improve. I would let them eat when mom is available and letting them nurse. Good luck and have a great day!