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If the mother dog is pushing one particular puppy away, instead of drawing him near her, you should be concerned. A puppy not huddled up with littermates and his mother will not get the food or warmth that he needs to thrive. A newborn puppy can become a weak puppy within a matter of hours. There are certain signs to check for to see if your puppy is having serious problems such as:  Cold to the touch or cold mouth Weak suckle reflex when the fingertip is gently placed in mouth Limp or poor muscle tone: head hangs down and legs don’t pull back when lightly tugged Inability to nurse Feces on the rear: can indicate diarrhea (a serious issue) Discharge from the umbilical stump Non-stop crying You should check all your puppies’ weights on a suitable scale twice a day. Kitchen scales will do, as long as you clean them well afterwards or even use them just for puppy weigh-ins. The weight can be taken in grams or ounces, just be consistent. They should never lose weight, instead they should gain about 10% of their birth weight each day after the first day of life. This indicates they are getting enough milk. Weights should be recorded in a notebook or spreadsheet so you can track their progress for the first two weeks of life.
Make sure the mother dog is taking care of all of her puppies. Look for signs of trouble. Check puppies regularly.