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There are over 200 breeds of dogs recognised by the Kennel Club.
These breeds vary substantially in size, purpose, conformation and
genetics. While all dogs are somewhat similar from a physiological
standpoint (they all have a heart, kidneys, a digestive system, two
eyes, and so on), there are many differences from breed to
Breed differentiation can be traced back to early domestication.
From wild dogs and wolves, man noted certain characteristics in
early-domesticated canids that were useful to human survival. From
sight hunting to tracking by scent, from pointing game to guarding
camps, dogs began to be bred for specific purposes. Now, centuries
later, the breeds have become distinct entities that reflect these
early uses even if societal progress has made their original
function of less importance.
This diversity of breeds, specifically the variation in breed
size, has created challenges for veterinarians, nutritionists,
kennel managers, and breeders. Breed size often reflects different
metabolic rates, different growth rates, and different longevity.
For example, a 5 lb. Chihuahua and a 150 lb. Newfoundland both
achieve complete development and growth within relatively similar
periods of time. But the 30-fold difference in mature size between
these two dogs means that the Newfoundland's rate of growth (pounds
of body weight per month) and amount of tissue far exceeds the tiny
Chihuahua. Veterinarians and nutritionists must consider these
disparities from a health care and nutritional standpoint.
The Small Breeds
Small and toy breeds have a higher energy requirement per unit
of body weight than do the large and giant breeds. This occurs
because metabolic rate is related to total body surface area. Since
the smaller breeds have a higher ratio of surface area to body
weight than large breeds, they require more energy per unit of
weight (pound or kilogram). In addition, the small breeds have
relatively small stomachs so their ability to consume food is
Diets formulated for small breeds should have higher energy
content and a more nutrient-dense nutritional matrix than diets
designed for larger breeds. High digestibility is also an important
factor, so that optimal nutrition can be provided in small meals.
Kibble size and shape should also be designed specifically for
small mouths to aid in chewing and consumption.
The Medium Breeds
Small and large breeds have specific nutritional and health
needs that are well documented. But, the medium breeds like
Beagles, Spaniels, and the herding dogs fall "in-between". Some of
the nutrition-related problems of large breeds, like the
developmental bone problems, do occur occasionally in medium
breeds. Medium breeds have a moderately high energy need, depending
on their lifestyle. As nutritionists and veterinarians determine
the health and nutritional needs of these intermediate-sized breeds
and develop diets that offer optimal nutrition for them, some of
the needs of small breeds should be considered, as well as some of
the needs of large breeds.
Management of Blood Sugar Response in Small and Medium
Since starch is the primary dietary component responsible for a
rise in blood sugar after a meal, this nutrient class deserves
close attention in the diets of small and medium breeds. Certainly,
the management of healthy blood sugar levels is desirable in large
breeds, but the smaller breeds benefit from this control as
Control of blood sugar may be impaired in several life stages or
conditions. Diabetes, obesity, pregnancy, and aging can alter the
ability of dogs to regulate their blood sugar. The ingestion of
food results in a post-meal rise in blood sugar followed by a rise
in insulin in the blood. Animals that have an abnormal ability to
control blood sugar often have difficulty storing glucose; as a
result, their blood sugar may remain high for longer periods of
time than in those with normal blood sugar control. It is
advantageous to reestablish a state of normalcy in blood sugar more
quickly in these impaired animals, and diets that help minimize
that rise in blood sugar after a meal are of benefit.
It is well documented that different starch sources affect the
after-meal blood sugar rise and insulin response in different
magnitudes. Scientists have assigned a "glycemic index" to many
starches for humans as a way to rank foods comparatively based on
the blood sugar levels they produce.4Since most carbohydrates in
food are directly broken down to provide blood sugar (glucose),
their influence on glucose metabolism can be substantial.
Research conducted by The Iams Company documented the influence
of starch source on post-meal blood sugar levels in dogs. In this
experiment, the test diets fed varied only in their starch source.
Results indicated that the source of starch influenced both the
blood sugar response to a meal and the insulin response of the
pancreas. Minimizing this response is desirable because it helps
stabilize blood sugar levels for sustained energy. Both glucose and
insulin were greatest when rice was used as the starch source. The
glucose response was minimized when sorghum was consumed as the
starch source while barley minimized the insulin response. Thus,
diets with sorghum and barley as the carbohydrate sources appear to
be most effective in reducing the blood sugar response to a meal in
It is important to manage blood sugar levels in the dog after
meals because there is a common relationship between poor glucose
metabolism and obesity in pets. In addition, the other conditions
mentioned earlier (diabetes, pregnancy, and aging) are associated
with impaired blood sugar responses to a meal. The challenge for
dog owners is to provide a diet that promotes a more level blood
sugar and insulin response. Dog owners can help meet this challenge
by feeding diets with a carbohydrate blend of sorghum and
Large breed nutritional needs
Large and giant breed dogs are some of the most popular of the
modern breeds. However, breeds that reach a mature body weight of
over 50 pounds have a propensity for a number of developmental bone
problems that can be responsive to nutrition. The association
between nutrition and skeletal problems has been the focus of
extensive nutritional research in recent years, and in particular,
the large breed puppy.
Research has documented that improper feeding during growth is
associated with several skeletal disorders in large and gian breed
dogs. About 22% of dogs less than one year of age are affected by
developmental skeletal disorders and more than 90% of these cases
are influenced by nutrition.6Two nutritional scenarios that can
contribute to these disorders are 1) free choice feeding of a diet
with excess calories, and 2) supplementation with calcium during
the growth phase of the puppy. The onset of developmental disorders
of the bones is usually associated with the rapid growth of the
long bones. The most common of these disorders are canine hip
dysplasia (CHD), osteochondrosis, and hypertrophic osteodystrophy
The Developmental Disorders
Canine hip dysplasia is a complex biomechanical disease of the
hip joint. Typically, the surfaces of the hip joint socket and the
surface of the head of the femur are not congruent. This results in
varying degrees of laxity, or looseness in the joint which, in
turn, determines the severity of the condition. The laxity of the
joint can lead to remodeling of the joint with resultant arthritis.
Clinical signs vary from severe, crippling lameness at a young age
to no signs throughout life. Canine hip dysplasia is caused by many
factors. Genetics are very important, as are trauma to the joints
and other environmental factors. Of these environmental factors,
diet and growth rate are very important, especially between the age
of 3 and 8 months. Puppies with excessive weight gain during this
period have a higher frequency of serious changes in the hip joint
and resultant degenerative changes in that joint than pups that
grew at a slower rate.
The osteochondroses, one of which is osteochondritis dissecans
(OCD), are characterized by minute disruptions in the maturation of
cartilage. While these conditions can occur at multiple points in
the skeleton, the most important locations are the shoulder,
stifle, hock, and elbow. Osteochondrosis can lead to an acutely
inflamed joint or degenerative joint disease involving the
cartilage surface. Osteochondritis dissecans occurs when a tiny
divot-like flap of cartilage separates from the underlying bone,
exposing the bone to joint fluid. While many factors, such as age,
gender, and breed are incriminated in OCD, excess weight gain and
supplementation with calcium have received the most attention from
a nutritional standpoint. Breeds that commonly exhibit OCD include
Great Danes, Labrador Retrievers, Newfoundlands, and
Hypertrophic osteodystrophy also occurs primarily in large and
giant breeds and is characterized by excessive bone deposits and
retarded bone resorption near the distal radius, ulna, and tibia.
As the disease progresses, soft tissue damage occurs around the
large bony deposits. Pain and swelling with concurrent lameness and
fluctuating fever is common. Some of these puppies then fail to
Genetics is an important factor in most developmental diseases
of the bone. But, if heredity were the only factor, these
conditions would have been eradicated long ago through selective
breeding. A heritability coefficient of 40% has been suggested for
CHD. This means that about 60% of the influencing factors for CHD
are environmental. Of these environmental factors, nutrition is
recognized as an important one. While many nutrient classes have
been investigated, data indicate, again, that excess calories and
excess calcium are the two most important nutritional factors.
Inexperienced owners of large breeds sometimes think, "bigger is
better". This can lead to feeding excess calories during the
crucial growth phase of the puppy's life. Over supplying calories
to a puppy can lead to a rapid, but unhealthy rate of growth. Not
only does over-feeding lead to increase in body mass, which can
stress growing bones, rapidly growing long bones can be inherently
weaker than bones growing at normal rates. The mechanism for the
effect of excess calcium is more complex. High dietary calcium
leads to high calcium levels in the blood, which stimulates the
body's natural mechanism to maintain a normal state. Through the
hormone, calcitonin, the normal maturing of cartilage is slowed and
the rate at which bone resorbs calcium is retarded. Chronic
suppression of these functions by excess calcium results in
increased thickening of developing bone. This may lead, in turn, to
developmental bone and joint problems. In an extensive study
conducted in growing Great Danes, over-nutrition was found to be a
contributing factor in the development of orthopedic problems.
In this study, puppies fed a calorie-restricted diet had fewer
developmental orthopedic problems than did puppies fed unlimited
calories. Typical problems observed included enlargement of the
rib-cartilage junctions, hyperextension of the carpal joints,
enlargement of the growing areas of the long bones, and sinking of
the "wrist" joint on front legs and hock on rear legs. This work
has be corroborated in other large breeds as well as other Great
Danes since this original study.16-18From a practical standpoint,
the adult size of a large breed puppy is determined primarily by
genetics, i.e., the size of its parents. Increasing the caloric
intake of a puppy merely increases the rate at which the puppy
attains this weight. The puppy that grows at a slower, more
appropriate rate will eventually weigh the same as its faster
growing littermates, but it will be less likely to develop joint
and bone problems.
Another misconception about nutrition and developmental bone
problems concerns the role of protein in the diet. The level of
this nutrient class in puppy diets has also been implicated as
influencing the incidence of these conditions in large breed
puppies; however, research has not supported this theory. Studies
conducted by Nap and colleagues documented that Great Dane puppies
fed diets with a range of protein levels (31.6%, 23.1%, and 14.6%)
from weaning to 18 weeks had no differences in either calcium
absorption or developmental bone diseases.20Protein is not
considered an important factor in the cause of developmental bone
diseases in the growing large breed puppy.
Calcium supplementation is another common feeding practice used
by inexperienced owners of large breed puppies. Research has
documented that excess dietary calcium can negatively influence
skeletal development in large and giant breeds. In an 18-month
study conducted by The Iams Company and Auburn University, Great
Dane puppies were fed one of three diets with levels of dietary
calcium of 0.48%, 0.8%, and 2.7%. The pups fed the high-calcium
diet accounted for 86% of the lameness found in the study.
Other studies documented that Great Dane puppies were not able
to slow down the absorption of excess calcium until they were about
seven months of age. Large breed puppies, therefore, should receive
adequate but not excessive dietary calcium. From a practical
standpoint, a level of 0.8% dietary calcium is beneficial for large
and giant breed puppies.
Some breeders and owners attempt to utilize an adult maintenance
diet to control calcium and energy intake in rapidly growing
puppies. If the adult diet has a typical (1.1%) calcium level, the
puppy will still consume excess calcium when fed this type of food.
A diet with normal energy levels coupled with lower calcium levels
is the ideal for large breed puppy nutrition. This type diet is
available commercially as a "large breed puppy" food.
The diversity of dog breeds developed by man has led to
interesting idiosyncrasies in conformation, personality, and
nutritional needs. Breeders and owners can help their breed
maintain a healthy lifestyle by utilizing well-researched
nutritional findings specific to certain breeds and breed sizes.
Small and medium breeds often need a higher calorie level to
support higher metabolic rates. All breeds can benefit from a diet
that helps manage healthy blood sugar and insulin responses to meal
by using barley and sorghum as the primary starch sources. Large
and giant breeds need moderate calories and calcium levels during
their growing months. Owners and breeders who are familiar with the
special health and nutritional needs of their breeds are more
likely to supply optimal nutrition to their dogs.
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