A 12-week-old, male, purebred Jack Russell Terrier puppy
Puppy
Small and toy breed dogs have a higher energy requirement per unit of body weight than larger breeds, because they have higher ratios of surface area to body weight.
There is wide variation in caloric requirements or energy needs between pets. Since small and toy breeds only require relatively small amounts of food and owners tend to carry them, they are predisposed to putting on weight. Puppies should be fed as individuals to maintain normal growth and a lean, healthy body condition. Purina Body Condition Score and weight should be continually monitored at home and at regular veterinary appointments.
"Small and toy breed puppies such as [puppy’s name] should eat puppy food until they reach full skeletal maturity, which occurs between 6 and 10 months of age. Food can be offered free-choice, provided body condition and weight are monitored to ensure weight gain is not excessive, until your puppy is 4 months old. After that, a switch to measured meal feeding can help control food intake and reduce the risk of unwanted weight gain."
Assess your dog's Body Condition in just 3 simple steps.
Case, L. P., Daristotle, L., Hayek, M. G., & Raasch, M. F. (2011). Canine and feline nutrition (3rd ed.). Mosby. doi: 10.1016/B978-0-323-06619-8.10025-8
Lawler, D. F. (2008). Neonatal and pediatric care of the puppy and kitten. Theriogenology, 70, 384-392.