Toy dogs may look cute, but many were bred for work. The Yorkshire Terrier, for instance, was reared to hunt rats in the cotton mills of Northern England. This accounts not just for its size, but also its curious and highly active disposition. Owners report that these tiny dogs often enjoy long walks and plenty of exercise, so one might expect them to be hearty eaters as well.
However, pet obesity is now a concern for all sizes of dogs. So it is important to make sure that even yappy Yorkies are not overfed. This is especially true when puppies are maturing as weight gained during this period can be hard to shift later on.
To make sure that dogs are always fed the right amounts of food, pet nutritionists have carefully worked out the canine energy requirements for each life stage. This ensures that the animals are only fed what they need to grow steadily and maintain a healthy weight. In the United States, for instance, the National Research Council (NRC), has published an equation calculating puppy energy requirements.
But energy requirements of toy breed puppies are unknown and it is unclear whether feeding guidelines should differ between breeds. This is particularly worrying as small and toy dog breeds are fast gaining popularity. There is increasing concern that owners do not have correct information on the quantity of food these miniature mutts require.
To address the problem, a WALTHAM research team decided to track the energy requirements of 22 Yorkshire Terrier (YT) puppies over their first year of life.
Energy intake, body weight and body condition scores (BCS) were recorded from 10 to 52 weeks of age. Every 12 weeks, health was monitored by veterinary examination and routine testing. Puppies remained clinically healthy with normal skeletal development throughout.
The pups energy requirements were then compared with those predicted by the NRC and those previously observed in large (Labrador Retriever) and medium (Miniature Schnauzer) breed puppies.
The team found that the NRC equation overestimated YT energy requirements by as much as 40% in some instances. This is most pronounced between 10 and 20 weeks of age. Energy intake was lower in YTs than Labradors until 29 weeks and lower than Miniature Schnauzers between 16 and 25 weeks.
“The data indicate that there are breed-related differences in energy requirements for growth,” says WALTHAM’s Janet Alexander who led the research. “Accurate feeding guides are essential if under and overfeeding are to be prevented. Small and toy breeds have been identified as being especially prone to becoming overweight which has in turn been shown to lead to reduced life expectancy and a number of pathological conditions.”
The NRC 2006 equation calculating the energy requirements of puppies was developed from equations which do not take breed differences into account. If used as the sole guideline for feeding the Yorkshire Terrier puppies, this estimate could result in excess energy intake and hence excess body weight. One explanation for the overestimation of energy requirement could be the level of physical activity of the Yorkshire terrier puppies in these studies. If activity was low, energy requirements would be similarly reduced. However, the dogs in the present study were housed in surroundings as similar to a domestic household as can be achieved in a kennel environment. They had a standardised care package including exercise and play sessions.
Although differences in activity level in kennelled dogs may affect energy requirements compared with the pet population, this is unlikely to influence the between-breed differences in growth pattern observed here, as all the dogs were kennelled under the same conditions. However in future studies activity monitors could be used to compare the physical activity levels of puppies of different breeds.