Adapting the food to the dog’s size

If you’re looking for an example of the range of sizes among dogs, imagine a Great Dane next to a Chihuahua. This huge difference in size also has consequences for how their bodies work. Duration and magnitude of growth, size of jaws and teeth, energy requirement and physical activity, relative weight of the digestive tract, predisposition to certain diseases and average life expectancy are all affected by the dog’s size, and all these factors must be taken into account when choosing its food. Obviously, the main principles are the same, but the differences between dogs of different sizes and sometimes between breeds means that tailoring the food to specific demands is beneficial in every stage of life.

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Tailoring nutrition to the puppy’s size

Differences in size between puppies are noticeable as soon as they are born. A Poodle whelps one, two or three puppies each weighing 150-200 grams (around 5% of the mother’s weight), whereas each of the eight to ten puppies in a Newfoundland’s litter weigh 600-700 grams (1% of the mother’s weight). While a giant-breed adult weighs 25 times as much as a small-breed adult, in newborns the same ratio is just six to one. This explains why giant breeds have to grow much more and for much longer than small breeds. The duration and magnitude of growth are in proportion to the final weight of the body.

© Diffomédia/Royal Canin
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Small, medium and large breeds

The variation in weight and size between the various dog breeds (ranging from 1kg to 100kg) is one of the biggest in the natural world. Adult dogs are classified into one of four groups: small breeds weighing less than 10kg, medium-sized breeds weighing between 11 and 25kg, large breeds weighing between 26 and 45kg, and giant breeds weighing more than 45kg. This size variation involves morphological, physiological, metabolic and behavioural differences between the various breeds.

Cette amplitude de variations entraîne des différences morphologiques, physiologiques, métaboliques et de comportement chez les différentes races :

Average lifespan is 15 years for small breeds, 13 years for medium-sized breeds, 10-11 years for large breeds and often less for giant breeds.

Magnitude and duration of growth: by the time it reaches adulthood, a member of a small breed will weigh twenty times its birthweight, a ratio that is fifty in medium breeds and eighty or more in large breeds. A small breed reaches adulthood at 8 months, whereas a large breed does not do so until between 18 and 24 months.

The weight and number of puppies in a litter also differ. Small-breed females will whelp on average three puppies, each weighing almost 5% of their mother’s body weight, whereas large breed females will whelp between eight and twelve puppies, each weighing barely 1% of their mother’s body weight. Proportionally, the size of some organs differs too. For example, relatively speaking a large breed dog’s digestive tract is half the size of a small dog’s.

The energy requirement of a 50kg dog is not five times greater than that of a 10kg dog but instead it is 3.3 times greater, because the dog’s metabolism is adapted to its weight.

The energy requirement depends not on body weight but on metabolic weight (75% of the former), which takes account of body shape and surface area.

Temperament also differs with size. Large breeds are generally calmer than small breeds, although they do need more living space.

Some hereditary diseases, such as hip dysplasia, are more likely to affect large dogs.

These differences between small, medium and large breeds have major consequences for health, diet and relationships between humans and dogs.

– By the age of three months, a small-breed puppy weighs half of its adult weight. A large-breed puppy will not reach this milestone until it is five or six months old.

– A Poodle reaches its adult weight around eight months of age. By that time it weighs twenty times its birthweight. A Newfoundland will continue to grow for at least another ten months, and by the time it is fully grown it will weigh around a hundred times what it did at birth.

The size of the breed demands special adaptation.

– At 3 months old, a Terrier puppy weighs 2-3 kg and a giant breed puppy 18-20kg. One obvious difference will be the size of their jaws – the Terrier puppy will find it difficult to grasp a medium-sized kibble, which will often result in it rejecting its food, whereas the giant breed puppy will spill a lot of its food. It is therefore a much better idea to serve kibbles that are tailored to the size of the breed, be that small, medium, large or giant.

– Large-breed puppies, whose growth period is long and intense, are especially susceptible to skeletal and joint problems, including limb defects, bone deformities and joint lesions. The first part of growth is mainly concerned with bone development, although the muscles also start to grow. This means that a puppy that eats too much (i.e. takes in too much energy) will put on too much weight and grow too quickly. This extra weight on the skeleton will increase the risk of bone deformity and joint problems (dysplasia). Limiting the energy concentration of a food for large breed puppies and feeding a correct daily amount will help control the speed of growth and so minimise these risks.

– A large breed puppy needs more calcium than a small breed puppy. A 20kg puppy only eats one and a half times the amount of a 10kg puppy of the same age. If it eats the same food there is an obvious risk of calcium deficiency. The calcium content in the food therefore needs to be increased for large breed puppies. On the other hand, large sized puppies are also more sensitive to excessive calcium intake. It is important to emphasise here that adding a dietary complement to a complete food formulated for the growth phase is at best unnecessary and at worst dangerous for the animal, unless prescribed by the veterinarian.

© Diffomédia/Royal Canin
© Diffomédia/Royal Canin
© Diffomédia/Royal Canin
© Diffomédia/Royal Canin
© Diffomédia/Royal Canin
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Should a growing puppy be given calcium supplements?

Wild carnivores eat entire carcasses, including the intestines and their contents, flesh and bone. Bone contains calcium, which is needed for essential processes such as blood coagulation and the nerve function, as well as bone calcification during growth. Bone can release calcium if the animal does not consume enough to cover what it needs to keep vital processes running. The skeleton can therefore serve as a calcium store.

When a dog eats only meat, its bones cannot mineralise correctly and cannot provide calcium for the vital processes. The bones will be weakened. To prevent this, dogs need calcium (and other mineral) supplements alongside their regular meat diet during growth.

Should a puppy be given calcium supplements when its diet is balanced and adapted?

Young carnivores absorb calcium from their food so their bones can mineralise during the growth phase and to keep other vital processes running. During growth, puppies absorb almost 100% of the calcium in their food if they receive too little calcium and 40% of the calcium in their food if they are on a diet specially formulated for puppies, containing 1-1.3% calcium by dry matter.

However, research has shown that puppies continue to absorb 40% of the calcium in their food in the event of excessive consumption. As a consequence, they absorb 40% of the excessive calcium. This surplus disrupts the growth and development of the skeleton, with such consequences as osteochondritis (including shoulder dysplasia), curved bones and panosteitis (growing pain).

Should a puppy be given vitamin D supplements when its diet is balanced and adapted?

Most vitamins are contained in foods or can be synthesised by the dog (such as vitamin C). However, the dog is not able to make vitamin D through the skin, unlike many mammals (including humans). If a dog does not find enough vitamin D in its food it will develop severe skeletal abnormalities: rickets (fragile, curved bones and cartilage proliferation).

Balanced foods for puppies provide 500 IU of vitamin D per kg, with a certain margin for safety’s sake. However, excess vitamin D in a puppy’s food can lead to disruptions in cartilage development similar to osteochondritis. As a consequence, excess vitamin D intake must be avoided. Vitamin D supplements alongside a balanced dog food can be harmful.


Professor Herman Hazewinkel,
University of Veterinary,
Medicine Utrecht, (Netherlands)

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