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Diet-Related Skeletal and Joint Diseases

People purchase dogs and cats for many different reasons. For companionship it is much less expensive and less troublesome to own a small-size than a large-breed dog. Ownership of a large-breed dog usually offers people a more athletic pet that can also fill an image of the type of dog an owner wants. Often a puppy is selected with hopes to mature into the biggest dog for its breed. Owners select the largest puppy in a litter and ask for feeding advice to insure growth to that size. They will feed whatever it takes to gain that size. If everything is done to satisfy this owner's wants, it is very likely that the animal will develop one or more orthopedic problems.1 Diseases of the joints and skeleton are very important and often serious problems in large and giant breed dogs.

Diseases Caused by Overnutrition1-3

Hip dysplasia has been and continues to be very common, accounting for up to one-third of all orthopedic cases seen by veterinarians. This degenerative joint disease results in a shallow acetabulum and flattened femoral head. The hip joint is partially luxated and shows secondary arthritis. Hip dysplasia occurs in one out of 60 dogs of all sizes. The risk in giant and large breed dogs is 20 to 50 times more likely than others. Overnutrition is an important cause.

Many dogs with hip disease have problems in other bones and joints. One of these is hypertrophic osteodystrophy, which by definition means excessive nutrition resulting in bone malnutrition. Bony changes cause lameness and affected bones are hot and painful. Excessive intake of protein, energy, calcium and phosphorus accelerates growth and induces the problem.

Osteochrondosis dissecans is characterized by a discontinuity between the articular cartilage and the osseous epiphysis. The changes may include the formation of cartilaginous flaps or free cartilaginous bodies (joint mice). The disease most commonly affects the upper humerus and sometimes affects the stifle, elbow, and hock joints. Larger breed dogs are most commonly affected. Causes are overnutrition, accelerated growth, hypervitaminosis D, and calcium deficiency.

Enostosis (eosinophilic panosteitis) is another disease of bone causing lameness and pain. Its likely cause is overnutrition.

Elbow dysplasia develops in some dogs where parts of a bone in the elbow fail to unite with others during development and growth.

In canine wobbler syndrome the spinal canal is unable to expand during growth because normal bone remodeling in the cervical spine fails and vertebrae do not develop normally; the vertebral canal narrows and nerve function is impaired. Overnutrition during growth is the cause.

Many degenerative diseases of bones and joints have a common basis. Undoubtedly, dogs inherit a tendency to develop these diseases. There is another important factor, however. Nutrition, particularly excesses of energy, specific vitamins, minerals, and to some extent proteins affect bone development in many ways that are mostly detrimental. Nutrition affects the development of hip dysplasia and the above-mentioned problems, some things that proper feeding can control.

How Overnutrition Causes Bone and Joint Diseases
Hip dysplasia is a disease of development; puppies are not necessarily born with the problem. The problem develops during rapid growth in larger-sized animals. Containing growth rate reduces both its frequency and severity. Unfortunately, quality of larger-sized dogs is often judged by size, with the largest size ideal. People believe that dogs achieve this ideal size through overfeeding for maximum growth. That is incompatible with the development of optimal skeletal growth, however. Moreover, nutrition does not alone decide final size in an adult dog. Underfed puppies eventually grow to the same size as those overfed. Overfeeding causes puppies to be overweight with little effect on skeletal size, bone length and diameter. People often judge a puppy's eventual desired size by the size of its paws. Overfeeding after weaning does not affect paw size. Overfeeding studies to promote weight gain in German Shepherd puppies during the first two months of life showed an increased incidence of hip dysplasia at a later age. In another study, scientists compared hand-reared puppies taken by caesarian section with puppies raised by their nursing mother. The latter puppies had hip dysplasia more frequently and with greater severity than the bottle-fed puppies. The difference was due to nursing providing more food. The first six to eight months of development are most critical for development of hip dysplasia. Feeding to support normal weight gain rather than to support maximum weight gain is essential to maintaining a low incidence of hip dysplasia.

Overfeeding to promote rapid growth prematurely stops some skeletal development. During normal growth and development bones continue to grow and mature even after it appears that body size no longer increases. Overfeeding puppies retards bone development so that the coxafemerol acetabulum stops growing several months earlier than in puppies on a calorie-restricted diet. Overfeeding has similar effects on skeletal development in many other animals. Restricted food intake should reduce other developmental bone and joint problems in rapidly growing dogs. Unfortunately, little can be done to help these problems after they appear,  making prevention important.


Diets Promoting Overfeeding
Studies on overfeeding and hip dysplasia were done with puppies eating a commercially prepared food. Puppies were overfed a food formulated to support growth. These diets usually contain more than the National Research Council's (NRC) recommendations for metabolizable energy, calcium, phosphorus and protein for a growing puppy. Pet food manufacturers use the NRC recommendations and add a "fudge factor" to increase nutrients 25 percent. This permits formulation of a complete and balanced diet without its testing in a feeding study. Puppies overeat when fed such foods free-choice especially because they are formulated to have optimum palatability and acceptance. Puppies eat more than to satisfy growth and caloric needs and many orthopedic problems develop. Restricting food consumption so that 17 percent less commercial growth diet is consumed reduces degenerative skeletal diseases. Growth in such puppies could be retarded. A 17 percent restriction does not affect eventual body size at eight to nine months, however.  More rapid growth of puppies after weaning does not translate into larger dogs at maturity.

Excessive weight gain is almost entirely due to consumption of excess calories. Dog food supplies calories in primarily carbohydrate and fat. Carbohydrate minimally promotes hip dysplasia unless carbohydrate consumption is so great that weight gain exceeds the ideal. When either dietary carbohydrate or fat contributes excess calories, orthopedic problems are more likely. Excess calories are fed easier with fat than with carbohydrate. Puppies consume more calories with high-fat diets than with cereal based low-fat diets because high-fat diets are more palatable. A fat-based diet containing the same number of calories as a carbohydrate-based diet is smaller volume and contributes less to satiety. Also dietary fats burn fewer calories for conversion to a pound of adipose tissue than the same number of carbohydrate calories.

Studies report that high-protein diets do and do not promote orthopedic problems. Animal proteins are usually high in fat and it is likely that feeding meat results in consumption of excess calories, something that has nothing to do with meat’s protein content. Puppy foods have more than adequate protein for supporting normal growth. Any excess protein will not stimulate faster growth of muscle or skeletal structures. The excess is converted to fat or burned for energy. Excess protein converted to fat results in weight gain just as excess carbohydrate.

Vitamin C and Orthopedic Problems3

Vitamin C may reduce hip dysplasia and possibly other orthopedic problems. Vitamin C is involved in collagen formation, the most important structural protein. This protein found in bone and ligament makes up 25 to 30 percent of all protein. An older study reported prevention of hip dysplasis by megadoses of vitamin C given during pregnancy and after birth to puppies until young adulthood. The study involved eight litters of German Shepherd puppies from parents with a history of producing puppies with hip dysplasia. The mothers received two to four grams of vitamin C per day during pregnancy. The puppies received calcium and vitamin supplements from birth to three weeks, 500 milligrams of vitamin C per day from three weeks to four months, and one to two grams of vitamin C from four months up to two years. None of the offspring had hip dysplasia. Unfortunately, no studies have been done since to confirm these results or to understand better this effect of vitamin C on hip dysplasia.

Excess vitamin C is believed to have little or no effect on the skeleton. Excess vitamin C affects ongoing bone mineralization and resorption, however. Excess vitamin C increases blood calcium that is likely to delay cartilage development and maturation and interfere with bone resorption. Both affect normal bone remodeling that occurs with growth. Thus, pet foods should not contain excess vitamin C.

Hip dysplasia can develop with degenerative disease in other joints. There is some evidence that the basis for this is increased joint laxity. Vitamin C might be necessary to prevent joint laxity; no one has proven that, however. A recent study showed that signs of chronic inflammatory joint disease (not restricted to hip dysplasia) improved when treated with vitamin C. No studies have been done to evaluate management with vitamin C specifically for dogs with hip dysplasia.

Mineral Imbalances and Orthopedic Problems1-3

Many believe that rapidly growing puppies of the large to giant breed dogs have a greater than usual requirement for calcium to sustain the growth of their large skeletal structure. Consequently, they believe strongly in supplementing these puppys’ diets with a vitamin-mineral preparation. The fear of not giving a supplement is that the animals will develop rickets and osteopenia. Rickets is a disease of young growing animals causing defective calcification of growing bone. Poorly mineralized bone deforms, giving the classical picture of rickets. Osteopenia is also bone calcium deficiency but involves adults. The cause is excess diversion of calcium during pregnancy and lactation. Rickets can be due to dietary deficiency of calcium, phosphorus or vitamin D. Humans have rickets from vitamin D deficiency caused by inadequate exposure to sunlight. Rickets is rarely seen in cats and dogs. It is never caused by inadequate sunlight.

Calcium Absorption and Excretion

Excess dietary calcium does not necessarily mean that excess amounts are absorbed. Calcium absorption is determined by dietary levels of vitamin D. The liver and kidneys convert vitamin D to a derivative that stimulates intestinal calcium absorption. Calcium regulation also involves its renal excretion. Thus, calcium and vitamin D supplements increase both calcium absorption and deposition. Bone calcium deposition and reabsorption are continuous processes. Their rate is at least 100 times greater in young growing animal than in adults. With a rate this high, abnormal bone growth happens easier in young animals than adults.

Calcium Supplements Promote Orthopedic Problems
Is there any harm in oversupplementing a growing puppy with a vitamin-mineral mixture? Long-term high calcium intake in large breed puppies can increase blood calcium and phosphate, retard bone maturation, retard bone remodeling, retard cartilage maturation, and disturb growth plates. Their manifestations include osteochrondrosis, bowed legs, and stunted growth. Young dogs have no mechanism to protect against excess dietary calcium. Excess calcium deposits primarily in bone, and with little reabsorption of bone calcium, severe abnormalities develop in the young growing skeleton. The normal remodeling process cannot compensate for these changes.

Calcium is the major factor for skeletal disease developing in growing giant-breed dogs. The dietary level of calcium is the cause. Once, rather than the level of calcium, many believed that an imbalance in the ratio of calcium to phosphorous was the cause. Most nutritional recommendations over the years emphasized the need for a proper ratio of the two minerals or skeletal disease would develop. Most blamed orthopedic problems on an improper ratio. Imbalances in the ratio of calcium to phosphorus occur most commonly when dogs and cats eat an all-meat diet. These diets often contain no bone. They are very high in phosphorus and low in calcium. The calcium to phosphorus ratio for an all-meat diet is likely to be 1:10 to 1:50. The proper ratio should be 1.3:1, or close to one. Feeding a high phosphorus and low calcium diet causes calcium removal from bones to maintain normal blood calcium. Bone calcium loss results in soft bones that fracture easily. 

The puppy of a giant breed is more likely than other breeds to show skeletal abnormalities when consuming excess calcium. This doesn't mean that excess calcium is harmless to smaller dogs. Excess calcium should not be fed to any breed of animal. Pregnant animals often receive excess calcium. No pregnant animal, whatever its size or breed, should receive excess calcium, however. Feeding high levels of calcium can produce osteochrondosis in the fetus. Supplementation of calcium (but not to give an excess) is necessary to prevent osteopenia during pregnancy and lactation. The amount given can increase if necessary during lactation.

Dietary Salt and Orthopedic Problems

Dietary salt concentration may be a factor in the development of hip dysplasia. Some studies show that adding excess of salts such as sodium and potassium, compared with others such as chloride, results in increased coxafemoral laxity and that leads to hip dysplasia.

Feeding the Large and Giant-Breed Dog  

No scientists agree on how much to feed a larger-size puppy. Although criteria for deciding the caloric content of a diet for the puppy that will mature to a large or giant size are generally lacking or scanty, one can estimate the amount of energy to feed. Tables in the section on normal dog requirements give the caloric requirements for growing dogs that will mature to all different sizes. These values are used as guidelines.

Diets for Feeding Large-Breed Growing Dogs


The following diets meet a growing dog’s requirements for all nutrients. They have no more than requirements for content of fats, vitamin D, calcium, and phosphorus. Feeding these diets to growing large-breed dogs will make it easier to prevent the rapid growth and weight gain that leads to orthopedic problems. They can be supplemented with 500 mg vitamin C. Vitamin B12 should be given by tablet several times a month or by feeding a food such as sardines that contains abundant amounts.

Chicken and Boiled Rice Diet

1/2 pound (weight before cooking) chicken breast meat (228 grams)
2 cups rice, long-grain, cooked (320 grams)
1 teaspoon vegetable (canola) oil (5 grams)
1/3 teaspoon salt substitute-potassium chloride
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/2 calcium carbonate tablet (200 mg calcium)
1 multiple vitamin-mineral tablet

provides 669 kcalories, 49.7 g protein, 10.1 g fat
see table for a puppy's caloric needs; caloric needs can be reduced up to 15% to minimize orthopedic problems.

Chicken and Potato Diet

1/2 pound (weight before cooking) chicken breast meat (228 grams)
3 cups potato, cooked with skin (369 grams)
1 teaspoon vegetable (canola) oil (5grams)
1/10 teaspoon table salt
calcium carbonate tablet (200 mg calcium)
1 multiple vitamin-mineral tablet

provides 665 kcalories, 49.9 g protein, 9.7 g fat
see table for a puppy's caloric needs; caloric needs can be reduced up to 15% to minimize orthopedic problems.

Chicken and Macaroni Diet

1/2 pound (weight before cooking) chicken breast meat (228 grams)
2 cups macaroni, cooked (280 grams)
1 teaspoon vegetable (canola) oil (5 grams)
1/4 teaspoon salt substitute-potassium chloride
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/2 calcium carbonate tablet (200 mg calcium)
1 multiple vitamin-mineral tablet

provides 653 kcalories, 54.5 g protein, 11 g fat
see table for a puppy's caloric needs; caloric needs can be reduced up to 15% to minimize orthopedic problems.

Cottage Cheese and Boiled Rice Diet

1 1/2 cup cottage cheese, 2% fat (339 grams)
2 cups rice, long-grain, cooked (320 grams)
1 teaspoon vegetable (canola) oil (5 grams)
1/4 teaspoon salt substitute-potassium chloride
1/4 teaspoon bone meal powder (1.5 grams)
1 calcium carbonate tablet (400 mg calcium)
1 multiple vitamin-mineral tablet

provides 760 kcalories, 55 g protein, 12.4 g fat
see table for a puppy's caloric needs; caloric needs can be reduced up to 15% to minimize orthopedic problems.

Cottage Cheese and Potato Diet

1 1/2 cup cottage cheese, 2% fat (339 grams)
3 cups potato, cooked with skin (369 grams)
1 teaspoon vegetable (canola) oil (5 grams)
1/4 teaspoon bone meal powder (1.5 grams)
1 1/2 calcium carbonate tablet (600 mg calcium)
1 multiple vitamin-mineral tablet

provides 756 kcalories, 55.3 g protein, 12 g fat
see table for a puppy's caloric needs; caloric needs can be reduced up to 15% to minimize orthopedic problems.

Cottage Cheese and Macaroni Diet

1 1/2 cup cottage cheese, 2% fat (339 grams)
2 cups macaroni, cooked (280 grams)
1 teaspoon vegetable (canola) oil (5 grams)
1/4 teaspoon salt substitute-potassium chloride
1/4 teaspoon bone meal powder (1.5 grams)
1 1/2 calcium carbonate tablet (600 mg calcium)
1 multiple vitamin-mineral tablet

provides 744 kcalories, 60 g protein, 13.4 g fat
see table for a puppy's caloric needs; caloric needs can be reduced up to 15% to minimize orthopedic problems.

 

Information on overnutrition causing orthopedic problems is recent. During the last fifty years veterinarians were usually happy to see owners bring in well-fed puppies of any breed. Owners were usually instructed and encouraged on feeding to make puppies look as "healthy" as possible. Healthy most importantly meant that they were not thin. Now it is known that this approach is wrong, especially if they will mature to a large size. If puppies continue to be fed so that owners can be proud of their size, orthopedic problems can be expected.

Management of Osteoarthritis

Osteoarthritis is one of the most common ailments of both young and old dogs: it is also a problem in some cats. The problem is helped by reducing weight in obese animals. Osteoarthritis is treated most often with nonsteroidal antiinflammatory drugs and sometimes with surgery. Drug treatment must be continuous and results are often unsatisfactory. These drugs cause serious side effects by inhibiting prostaglandin production. When its levels are reduced, gastrointestinal mucosa ulcerates. These effects are so severe that many will not use nonsteroidal inflammatory drugs in dogs.

Newer management of osteoarthritis includes dietary supplementation with forms of cartilage.4 This treatment has not found favor with clinicians but there have been no controlled studies to show that giving cartilage doesn't help. Dogs with moderate osteoarthritis causing clinical signs of lameness for four to five months have improved dramatically with cartilage supplementation.

Cartilage can be given in the form of a commercially prepared supplement, with an 80 pound dog receiving three 750 milligram tablets daily or three tablets daily containing a combination of chondroitin (400 mg) and glucosamine (500 mg). If a dog is fed chicken, the cartilage on the ends of bones can be easily removed after boiling and included in meal. It is not known why cartilage benefits animals with osteoarthritis. Some believe that glycosaminoglycans released from digested cartilage are absorbed and enter joints where they helps renew damaged articular surfaces. Cartilage given orally also inhibits intestinal absorption of toxins and that could benefit arthritis. Some cases of arthritis are associated with chronic inflammatory bowel disease, and the arthritis is suspected to result from toxic substances absorbed from the intestine. Cartilage is poorly digested so that no more than half is degraded. Cartilage is a complex carbohydrate that binds both bacterial toxins in the intestine and the intestine's mucosal surface. Both of these actions reduce toxin absorption. Because some animals can benefit from cartilage and the product is safe and relatively inexpensive, the first attempt in managing osteoarthritis should be to give cartilage. Patients given cartilage and responding have shown little or no lameness after three weeks.

Summary

In summary, many factors are involved in the development of hip dysplasia and other orthopedic problems. It is difficult to control factors such as breed predisposition other than by not breeding affected animals. That has not solved the problems. Other factors can be controlled. Maximum growth rate growth should be prevented. Growth rate can be controlled by restricting caloric intake 15 to 20 percent of usual recommendations; excess weight gain is important in the development of hip dysplasia. Restriction of caloric intake during growth has no affect on eventual size at maturity. Such restriction does determine normal skeletal integrity during and after growth.

Deficiency of specific nutrients is rare and should not be such a concern that excess of any nutrient is fed. Excess calcium and vitamin D cause orthopedic problems from the absorption of excess calcium. Excess nutrients are not harmless because the animal cannot compensate for excess of many. Larger size dogs may be less able to compensate than smaller animals. Rickets and other deficiency diseases are rare today. Many believe that canine orthopedic problems are largely caused by genetic defects, and culling of carriers is proposed. These problems were infrequent more than 50 years ago, at a time that not many dogs ate commercial pet foods. Many of these orthopedic problems are genetic problems but they appear because of overnutrition.

Owners are forced to feed puppies free-choice because they lack useful information to do otherwise. Pet food labels provide vague information on the proper amount to feed a puppy. As a result, owners give puppies as much food as they want. Instead of feeding puppies to look well-fed and with a size to be proud of, they should be fed amounts that allow them to appear lean and trim. Animals with osteoarthritis should be managed by weight reduction, where indicated, and by cartilage given orally.

References

1. Hazewinkel, Herman A. W. 1994. Skeletal Disease. In The Waltham Book of Clinical Nutrition of the Dog and Cat. edited by J. M. Wills and K. W. Simpson, 395-423. Oxford: Pergamon Press.

2. Kealy Richard D., Dennis Frank Lawler, Joan Marion Ballam, George Lust, Gail Keen Smith, Daryl Norman Biery and Sten Eric Olsson. 1997. Five-year Longitudinal Study on Limited Food Consumption and Development of Osteoarthritis in Coxofemoral Joints of Dogs. Journal American Veterinary Medical Association 210(2):222-225.

3. Richardson, Daniel C. 1992. The Role of Nutrition in Canine Hip Dsyplasia. Veterinary Clinics North America: Small Animal Practice 22(3):529-540.

4. Altman, R. D., D. D. Dean, O. E. Muniz et al. 1989. Therapeutic treatment of canine osteoarthritis with glycosaminoglycan polysulfuric acid ester. Arthritis and Rheumatism 32:1300-1307.