A nursing puppy may spit up after eating for several reasons. For one thing, milk is frothy; so burping up some is not unusual. Spit-up in the form of vomiting is a matter to look into. Think back to how you prepared and fed puppy milk to a nursing puppy to try to determine what may have caused the vomiting, then make the appropriate changes.
Feeding Too Fast
If you accidentally feed a nursing puppy too much food or feed too quickly, this may cause milk to bubble out the puppy's nose. It can appear that she is vomiting up the food. Try feeding less puppy milk; simply stop feeding before she's ready for you to stop. Observe how milk flows through the hole in the bottle. If the hole is too big, milk can flow too quickly and cause spit-up. If you are tube-feeding your puppy, rapid feeding may cause vomiting as well. Nursing puppies may drink mother's milk too quickly as well.
Food Too Cold
Puppy formula can be like Goldilocks's bed: Not too hot, not too cold, but just right. While food that is too hot can burn her mouth, food that is too cold can cause vomiting. Warm puppy milk before feeding to a temperature of 99 to 100 degrees Fahrenheit.
Problems Preparing Puppy Milk
If the puppy milk was not mixed properly or if something you used was not properly cleaned, your dog may vomit as a result. Always mix the formula following the directions on the package to avoid regurgitation. To prevent hygiene problems, refrigerate any prepared formula and discard after 24 hours. Thoroughly wash, rinse and dry bottles, feeding equipment and any dishes you used to prepare the formula. This prevents accidental contamination that may cause vomiting.
Should You Be Concerned?
Since vomiting represents fluid loss, puppies may experience dehydration and subsequent hypothermia as their body temperature falls due to inactivity. A puppy that consistently vomits may become hypoglycemic. If your pup experiences vomiting or diarrhea, appears less active than normal, does not want to nurse and is crying, take her to the vet. If your pup vomited but still wants to eat and has her energy, she likely experienced a problem with that meal. Still, call your vet to make him aware of the situation.