A puppy should never be taken from its mother before the age of 8 weeks. 10 weeks is optimal. Unfortunately, in the race to sell puppies, a breeder, store or individual may sell a Chihuahua puppy before it is the proper time.
When at all possible, do not buy or take a puppy until he or she is old enough. When the dog is forced to stop drinking the dam's milk, this can cause major problems.
A Chihuahua puppy may also not eat, or not eat enough because of a medical issue. Before you take matters into your own hands, the puppy needs a full and complete veterinary checkup. There are many medical reasons why the dog may not be eating, including stomach and intestinal problems.
How You Can Help
Once it has been determined that a Chihuahua does not have any medical reasons for not eating, the answer will most likely be that he or she was weaned too soon. You will need to start from the beginning and essentially play the part of the mother. For very small, undersized Chihuahua - often referred to as Miniatures
or Toys- a dropper will work best. For those a bit larger, a bottle may be best.
The goal will be to feed the puppy a milk replacer. As the body takes in nutrients, becomes stronger and gains weight, he can then be weaned onto solid food.
You will want to choose a formula that is vitamin and mineral enriched, easily digestible and highly palatable. Most come in a powder form that is then mixed with water as needed.
Do not use unfiltered tap water, since it can - legally - contain many chemicals including pesticides, factory run-off, lead, copper and even low levels of arsenic. Obtaining a filter for the kitchen tap or buying gallons of spring water are two choices.
Puppies will be hungry quite often and a replacer should be offered every few hours. The pup can be swathed in a blanket so that he feels safe and secure. It is recommended to weigh the pup once a day. There should be a gradual weight gain.
After one week, soft mushy foods can be introduced. For a very young Chihuahua that won't eat, meat based baby foods, cottage cheese, and yogurt are tempting treats. As the pup's body becomes accustomed to food, you can transition to regular meals. 4 meals per day, plus snacks are recommended for undersized Chihuahuas.