The growth rate of dogs varies according to the size of the breed. Large breeds of dogs such as the English Mastiff, Irish Wolfhound and Great Dane have a longer growth period compared to smaller breeds such as the Miniature Schnauzer, Cairn terrier and Papillon. The disparity between the growth rates of different dog breeds is due to their different energy requirements, which are affected by the dog's size, temperament and type of coat.
In 2004, the growth rate of dogs, as well as the body-weight changes during the growth period, was studied in 173 puppies that represented 12 different breeds. The study was published in the 2004 issue of the Journal of Nutrition by the American Society for Nutrition.
The breeds that were in the study were the English Mastiff, St. Bernard, Irish Wolfhound, Great Dane, Newfoundland, Labrador Retriever, Beagle, English Springer Spaniel, Cocker Spaniel, Miniature Schnauzer, Cairn Terrier and Papillon. The puppies were observed for a period of 12 months for small to medium-sized dogs, and 18 months for large breeds.
It was observed in the study that toy dogs experienced growth spurts until 11 weeks after birth, small to medium-sized dogs until 14 to 16 weeks and large breed dogs up to 5 months. The increase of body weight during this spurts on average was between 13 to 17 percent per week.
In the study, toy dogs and small and medium sized dog breeds were able to achieve 99 percent of their growth at around 9 to 10 months. Large dog breeds reached 99 percent of their adult weight at 11 to 15 months.