Feeding growing puppies (Proceedings)

There remains much confusion when it comes to feeding growing puppies. Many traditional recommendations of breeders and veterinarians, such as switching growing large breed dogs to adult food or not using growth diets at all, are no longer appropriate and may be harmful.

Types of diets

Part of the confusion may stem from the prevalence of diets formulated to meet AAFCO profiles or passing AAFCO feeding trials for "all life stages". These diets may be marketed as adult diets only (e.g. Purina Dog Chow) but may have been tested for puppy growth. Essentially, "all life stages" foods are puppy diets that are designed to also be fed to lactating bitches and adult dogs. This one-size-fits-all approach has advantages and disadvantages. For the multiple dog family, these diets may solve the problem of having to feed different diets to dogs of different ages and the generally higher caloric density can be helpful for high energy and working adult dogs. However, these diets often contain excessive calories for adult dogs at maintenance and potentially also for growing large and giant breed puppies. Even more importantly, the calcium content of many of these diets (especially high protein +/- grain free diets) may be inappropriate and even potentially deleterious to large and giant breed puppies.

Many of the concerns over feeding puppy food to large and giant breeds likely came about due to growth abnormalities in long bones and joints that were seen in growing puppies fed some of the earlier growth diets before the link between calcium and energy content and developmental orthopedic disease was discovered. These concerns have been mostly remedied by the development of large and giant breed puppy diets. Although there are no specific legal guidelines or definitions for large breed growth diets, in general these diets are lower in calcium and lower in energy density than "regular" puppy diets. These diets may also be supplemented with compounds such as glucosamine, omega-3 fatty acids, and chondroitin for potential orthopedic benefits. As there are no AAFCO guidelines for large breed puppy formulations versus those for smaller puppies, it is important to choose a diet produced by a reputable manufacturer. Diets that have undergone AAFCO feeding trials for growth are preferred; however, there is no requirement that large breed puppy diets be tested in large breed puppies versus smaller puppies. Therefore, it is incumbent on the puppy owner and the veterinarian to look for diets that have actually been demonstrated to be appropriate in large or giant breed puppies.

In the author's experience, the majority of (and the most severe cases of) nutrition related disease in growing puppies are the result of feeding home-prepared diets. Nearly all home-cooked diet recipes obtained online and in books are deficient in essential nutrients and often these nutrients are the ones most essential for growth. Growing animals are acutely susceptible to nutritional imbalance and the results of seemingly small errors in formulation can be lifelong. It is therefore extremely important that growing puppies not be fed home-prepared diets. Clients should be strongly encouraged to wait until the puppy has reached at least a year of age (small breeds) or 18 months (giant breeds) before starting a home-cooked diet if this is their preference. Clients should be advised to consult a board-certified veterinary nutritionist to ensure that an appropriate, nutritionally balanced, home-cooked diet is fed.

Likewise, raw diets, whether home-prepared or commercial, should not be fed to growing puppies. Not only are many of these diets (even commercial products) deficient in essential nutrients, but the risk of serious food-borne illness secondary to contamination is more acute in young animals with developing immune systems.

Developmental orthopedic disease (DOD)

Developmental orthopedic diseases (DOD) are common in large- and giant-breed dogs and include hip dysplasia, osteochondrosis, panosteitis, hypertrophic osteodystrophy, and a variety of others (eg, ununited anconeal process, fragmented coronoid process). These diseases have multifactorial pathogenesis and are largely influenced by genetics, biomechanical forces, and nutrition. Nutrition is now known to have a major influence on modifying a dog's genetic predisposition to developing DODs. Therefore, it is important to counsel the owners of large- and giant-breed dogs so that the incidence of these diseases is minimized.

There are two major nutritional risk factors for DOD - rapid growth and excess calcium intake. Of these, rapid growth caused by excessive calories seems to be most prevalent. Puppies will put excess calories into growth before adding fat mass, so even a slightly fat puppy is likely growing at an unsafe rate. This problem is compounded by the fact that not only do these puppies carry more weight on developing bones, but there is evidence that rapid skeletal growth results in bones that are less able to handle the stress of increased body mass. Multiple studies have shown that restriction of calories in growing large- and giant-breed puppies reduces the risk for hip dysplasia, osteochondrosis, and osteoarthritis while provision of inappropriate quantities of high calorie diets can increase risk of these conditions. In one well-designed study1, Labrador retriever puppies who were fed free choice versus sex-matched littermates that were fed 75% of their littermate's intake, had over two times the rate of hip dysplasia as their calorie restricted siblings. Likewise, radiographic prevalence of osteoarthritis in the hip and shoulder and severity of osteoarthritis in the elbow were significantly less in the calorie restricted dogs at 8 years of age2. Caloric restriction and slowed growth was also associated with a significantly longer lifespan (18-24 months) without additional morbidity3. Despite the conventional wisdom, caloric restriction does not alter the final size of the puppy, but alters the amount of time that it takes to reach adult size.

Excessive dietary calcium has also been linked to DOD. Unlike adult dogs, puppies have minimal regulation over intestinal calcium absorption for the first 6 months of life. Therefore excess dietary calcium is very readily absorbed even when the total body calcium exceeds physiologic needs. Hypercalcemia leads to increased secretion of calcitonin which in turn may result in aberrant calcium deposition in rapidly growing bones, leading to abnormalities. Although the National Research Council (NRC) safe upper limit for puppies has been set at 4.5 g/Mcal calcium, the recommended allowance is only 3 g/Mcal. The author generally looks for diets for large and giant breeds that contain between 3-3.6 g/Mcal calcium, to be cautious.

The practice of feeding adult diets to large breed puppies may in part have come about due to the observations that many adult maintenance diets have lower calcium contents (at least on an as fed basis) than puppy foods. However, these diets are likely to be deficient in essential nutrients (including calcium) needed for growth. Additionally, if nutrients are not compared on an energy basis, it is possible for excessive calcium to be fed to a puppy due to the necessity of feeding more of a lower calorie adult diet to meet energy requirements.

Many people still believe that dietary protein is a risk factor for DOD in dogs. However, studies have shown no effect of dietary protein when calcium and energy consumption are controlled.

General recommendations

Toy, small and medium breeds (< 50 lb adult weight) – Feed a growth diet or an all life stages formula that has passed AAFCO feeding trials until adult size is reached (or 1 year of age), then transition to an adult diet. Feed to maintain a body condition of 5/9 from the beginning of the growing period through adulthood. Most puppies should be meal fed; however, some toy puppies may benefit from ad libitum feeding or frequent meals for the first month or two after weaning. Puppies should be weighed and their food intake evaluated every 2 weeks during the active growth phase.

Large and giant breeds (> 50 lb adult weight) – Feed a large breed growth diet that has passed AAFCO feeding trials for growth until adult size is reached (12-24 months). Feed to maintain a body condition of 4/9 during growth and maintain a 4-5/9 throughout adult life. Puppies should always be meal-fed rather than allowed ad libitum consumption. Large breed puppy diets with higher or lower caloric densities can be used as needed to balance feeding amounts, nutrient needs, and individual metabolism. Puppies should be weighed and their food intake evaluated every 2 weeks during the growth phase.

For larger puppies of unknown parentage, or puppies of mixed breeds known to be prone to orthopedic disease (such as retriever and shepherd mixes), it is likely safest to meal feed them a large breed food and keep them lean. Transition to an adult maintenance diet can begin at 1 year of age.

It is important to discuss body condition scoring and weight management at all puppy appointments and reinforce this information when the puppy comes in for weigh-ins for heartworm and ectoparasite preventatives as well as at the spay and neuter appointment. Every puppy owner should be taught how to body condition score their puppy and sent home with a copy of a body condition score chart (5 and 9 point scales are readily available from pet food manufacturers and other sources such as the AAHA Nutritional Assessment Guidelines). At the time of spay or neuter, it is important to advise owners that energy requirements will decrease after surgery and many puppies will need to be fed less (up to 20% less). This is a good time to reassess the diet that is being fed and determine whether switching to an appropriate puppy diet with a different caloric density would be useful.

Growing puppies, especially large breeds, should not be supplemented with any vitamin or mineral supplements. These supplements are unnecessary when a balanced commercial diet is fed and can contribute to developmental orthopedic diseases. It seems to be becoming more common for breeders to insist that specific supplements are fed in order for the hip/health guarantees to be valid. This practice likely puts the puppies at greater risk of developmental problems but this information has clearly not been widely disseminated enough to prevent such restrictions. It is important to council owners about the risks of such supplements so that they can make an educated decision on whether to follow the breeders' recommendations. Breeder clients should also be educated as to the known causes of developmental orthopedic disease and ways of preventing the condition.

References

Kealy RD, Olsson SE, Monti KL, et al. Effects of limited food consumption on the incidence of hip dysplasia in growing dogs. J Am Vet Med Assoc 1992;201:857-863.

Runge JJ, Biery DN, Lawler DF, et al. The effects of lifetime food restriction on the development of osteoarthritis in the canine shoulder. Vet Surg 2008;37:102-107.

Kealy R, Lawler D, Ballam J, et al. Effects of diet restriction on life span and age-related changes in dogs. J Am Vet Med Assoc 2002;220:1315-1320.