Knowing what to feed a dog that weighs 350g (12.3 ounces) depends a great deal on the breed/body type and age, as well as the general health, of the puppy involved. A small-breed puppy at 350g would probably be fully mature and eating solid food. On the other hand, a large-breed puppy of the same weight might require tube feeding or soft food.
According to PetPlace.com, at eight weeks of age small-breed puppies require roughly 400 calories per day, while toy breeds require 225 calories per day. Many small and toy breed puppies will weigh approximately 350g, although the weight of each puppy will depend on the body type and build, as well as the activity level of each individual. The amount of food required to meet these caloric needs varies depending on the type of food being given to the puppy. Use the nutritional analysis on the food packaging to determine the number of calories provided in each ounce of food and progress as needed.
Orphaned puppies have particular nutritional needs. Medium and large-breed puppies that weigh only 350g are usually no more than one or two weeks old, far younger than the age at which they can eat solid food on their own. At this age, puppies hand-raised at home must be bottle-fed. While the frequency of feeding might make tube-feeding appealing, particularly in the large litters associated with medium and large breeds of dogs, use feeding tubes only if you have the training and education to do so.
Laura Michaels, breeder of the famed Kelrobin-Woodhaven line of Labrador Retrievers, indicates that a puppy weighing 350g (12 ounces) should receive 90cc (ml) of formula each day. Break this total into either six or eight feedings per day, resulting in either 15cc or 11.5cc feedings each time.
According to the Claws & Paws Veterinary Hospital site, it is possible to estimate the amount a puppy should eat by using its caloric needs as a guide. Puppies require 3.75 calories per ounce of their body weight per day during their first week, 4.50 calories per ounce per day during the second week, 5 calories per ounce per day during the third week, and 5.5 calories per ounce per day during the fourth week.
If your puppies are nursing on their dam but not gaining weight, then they might not be receiving sufficient calories for their needs. Use the Paws & Claws guidelines to determine how much supplemental feed that they would require if they were not feeding at all and adjusting up or down as needed. Following the fourth week, puppies can be, or might be, weaned onto solid food.