Diet-Related Skeletal and Joint

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.¹Diseases of the joints and skeleton are very important and often serious problems in large and giant breed dogs.

Diseases Caused by Overnutrition^1-3
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 Problems^1-3

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.