Nutrition Info

Breed and Size Specific Nutrition, Martin Coffman, DVM

There are currently about 150 breeds of dogs recognized by the American Kennel Club. When considering these breeds, plus those registered by the United Kennel Club, the Field Dog Stud Book, the Canadian Kennel Club, and the dozens of other registries worldwide, the diversity of breeds of domestic dogs becomes truly impressive! While all dogs are basically similar from a physiological standpoint, breeds vary substantially in size, purpose, conformation, and genetics.

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. This led to breeding for specific purposes including sight hunting, tracking by scent, pointing game, and guarding camps. The modern breeds have evolved into 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-pound Chihuahua and a 150-pound Newfoundland both achieve complete development and growth within relatively similar periods of time. However, the 30-fold difference in mature body size 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.

Small Breeds

Small and toy breeds have a higher energy requirement per unit of body weight than the large and giant breeds.1 This occurs because basal 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 (lb or kilogram [kg]). In addition, the small breeds have relatively small stomachs so their ability to consume food is somewhat limited.

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.

Medium Breeds

Small and large breeds have specific nutritional and health needs that are well documented. But the medium breeds, such as Beagles, Spaniels, and the herding dogs, fall somewhere 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.

Large and Giant Breeds: Special Nutritional Needs

Some of the most popular breeds are the large and giant. These breeds which reach a mature body weight of over 50 pounds have been the focus of numerous nutritional research studies in recent years, and in particular, the large breed puppy. These breeds have a propensity for developmental bone problems, but research has shown that these problems can be responsive to nutritional management. (For purposes of this discussion, the term large breed refers to both the large and giant breeds.)

Research studies documented that improper feeding during growth is associated with several skeletal disorders in large 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 nutritional factors. Two nutritional scenarios are important in causing these disorders in puppies: 1) free-choice feeding of a diet with excess calories, and 2) supplementing calcium during the growth phase. The onset of bone developmental disorders is usually associated with rapid growth of the long bones. The most common of these disorders are canine hip dysplasia, osteochondrosis, and hypertrophic osteodystrophy.

Developmental Disorders

Canine hip dysplasia (CHD) 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 (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 particularly important, especially between 3 and 8 months of age. 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 like 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 Rottweilers.

Hypertrophic osteodystrophy (HOD) also occurs primarily in large 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 eat.

Influences

Genetics. Genetics is an important factor in most developmental diseases of the bone. However, 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.

Overfeeding. 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 overfeeding lead to increased body mass, which can stress growing bones, but rapidly growing long bones can be inherently weaker than bones growing at normal rates.

Supplements. The mechanism for the effect of excess calcium is more complex. High dietary calcium leads to high-calcium levels in the blood that stimulate 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, in turn, lead to developmental bone and joint problems.

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Large Breed Nutritional Research

Results of Overfeeding. In an extensive study conducted in growing Great Danes, overfeeding 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 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 been corroborated in other large breeds, as well as other Great Danes since this original study.

From a practical standpoint, the adult size of a large breed puppy is determined primarily by genetics, that is, 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.

Results of calcium supplements. Nutrition research has documented that excess dietary calcium can negatively influence skeletal development in large and giant breed dogs. In an 18-month study, 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 incidence of lameness that developed. Other studies have documented that Great Dane puppies were not able to slow down the absorption of excess calcium until they were approximately 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.

Feeding Recommendations for Large and Giant Breeds

Current research clearly documents that the skeletal development of the growing large breed dog is best supported by feeding a diet that contains 26% protein (from high-quality, animal-based sources), 14% fat, 0.80% calcium, and 0.67% phosphorus. Supportive evidence for this recommendation is both convincing and compelling and is summarized in the Table below. A reduced dietary energy density, relative to typical growth food, provides for easier management of growth rate and results in a moderately slowed growth rate relative to the genetic potential for growth. This will result in the same ultimate mature body size and a skeletal structure that is better able to support the increasing body mass as growth progresses. Rapid growth rate and calcium supplementation are to be absolutely avoided with the growing large breed dog. Failure to follow an appropriate, scientifically justified feeding management regimen can result in a less-than-optimal skeletal structure.

Although dietary calcium is most often provided in excess of that needed by the growing large breed puppy, that is not always the case. A puppy raised on a homemade diet that contains high amounts of fresh meat may, in contrast, be receiving an inadequate supply of calcium. Feeding mostly meat, without an appropriate commercially prepared growth diet formulated specifically to meet the needs of the growing large breed puppy as previously defined, can easily result in dietary calcium concentrations below 0.48% calcium, which itself has been shown to produce suboptimal skeletal development.

Supplementing a high-meat diet with calcium to an appropriate concentration (0.80), although possible, is not the recommended strategy. Supplementation requires an accurate analysis of dietary calcium and phosphorus and a very specific addition of calcium to provide not only the needed calcium, but also to ensure that the calcium-to-phosphorus ratio is correct (1.2 to 1). Furthermore, the amount of supplemental calcium required will not remain constant over time since the content of calcium and phosphorus in the base diet will vary depending on the source of meat. It would therefore be extremely difficult, if not impossible, to maintain a constantly correct dietary supply of calcium and correct calcium-to-phosphorus ratio.

Management of Blood Sugar Response in Small and Medium Breeds

The management of healthy blood sugar levels is a desirable goal for all dogs, regardless of breed size. Since starch is the primary dietary component responsible for a rise in blood sugar after a meal, this nutrient class deserves particularly close attention.

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 animals 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 can be beneficial.

It is well documented that different starch sources effect the after-meal blood sugar rise and insulin response in different magnitudes. Scientists have assigned a glycemic index to many starches as a way to rank foods (for humans) comparatively, based on the blood sugar levels they produce.

Since 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 sorghum and barley as the carbohydrate sources appear to be most effective in reducing the blood sugar response to a meal in the dog.

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 barley.

Breed and Size Specific Nutrition: Conclusions

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.