Nutritional considerations for optimal puppy growth-
Dogs are a unique species in the animal kingdom, not least because of their hugely variable body-weight, from the Chihuahua weighing < 1 kg to the Saint Bernard that is more than 80 kg. In association to this large diversity, the rates and duration of growth vary. A small breed dog (adult weight < 10 kg) will multiply its birth weight around 20 times, reach half its adult weight at 3 months, and complete its growth by 10 months of age. The growth period for small breeds is specifically short and intense. Conversely, by one year of age, a large breed dog (adult weight 25 kg or more) will multiply its birth weight at least 70 times; it will reach half its adult body weight around 5-6 months and the growth period may last up to two years.
Small and medium breed puppies gain 20 g - 60 g per day with maximum daily weight increase seen around the post-weaning stage (i.e. 2-3 months). Conversely, maximum daily weight gain is generally reached around 3-4 months in large breed puppies and between 4-5 months in giant breeds. Daily weight gain in large and giant breed puppies remains high until 8 months and the weight of these breeds therefore increases considerably over a long period of time. One consequence of the differences in growth is that at weaning the growth of the bone tissue in a small breed is well advanced, whereas it has hardly started in a large or giant breed puppy. These differences in growth rates explain why large and giant breeds have a greater risk of disorders associated with growth and highlight the fact that the requirements of puppies of different breeds are not the same and must be tailored to specific needs.
Energy requirements for growth will vary depending on the age, sex, breed and environment of the puppy. During the first half of its growth, a puppy requires twice as much energy as an adult dog (in relation to its weight) (1). This increased requirement reflects the extra calories needed to support growth and retention of new tissues. The degree of increase depends on the rate and stage of growth. Younger puppies need more calories per unit of bodyweight than older ones, and large or giant breed puppies require more energy until an older age than puppies of small breeds. This very high requirement gradually decreases; by the time the puppy reaches 80% of its adult weight (i.e. at ~ 6 months for a small dog and 8-10 months for a large dog), it consumes only 20% more energy than an adult.
Females are generally lighter than males and reach their maximum growth rate earlier. This sexual dimorphism is much more pronounced in large and giant breeds than in small breeds and is important because it implies differences in requirements at the end of growth between the two sexes. Males have a longer growth period, and therefore have higher energy requirements over a longer period of time.
The exact caloric requirements, and thus amounts to feed, are extremely difficult to estimate in puppies because of wide variations even within a breed. Some recommendations based on the adult body weight have been published (2) but estimation of final adult bodyweight is difficult. Therefore growth curves should be considered as a guideline only, and the amount fed should be adjusted to maintain puppies in ideal to lean body condition. During the rapid growth period (2-8 months of age) it has been recommended that large breed dogs should not gain more than 100 g/day and giant breeds (> 35 kg) not more than 200 g/day. Another recommendation is that at 6 months of age puppies should weigh less than 60% of their adult body weight.
Skeletal abnormalities such as hip dysplasia, osteochondritis dissecans, radius curvus, stunted growth, and hypertrophic osteodystrophy are commonly associated with the growth of large and giant breeds, but quite rare in small breeds (3).
While the clinical behavior and the radiological features of these diseases have been clearly defined, little is known of their causes. Genetics has been shown to be a major component, but environmental factors such as nutrition and exercise clearly play a role, and may indeed affect the expression of undesirable genes. Nutrient excesses (particularly energy and calcium), rapid growth rates and excessive weight gain appear to be important factors contributing to the incidence of skeletal disorders.
It is important to note that some owners of large and giant breed puppies mistakenly overfeed their puppies on the underlying assumption that they will foster a larger and taller adult dog. This is simply not true; size is actually determined by the individuals genetics, and overfed puppies will simply grow faster and reach their adult size earlier, with an increased danger of disorders associated with growth. Accelerated growth rates place more strain on an immature skeleton, which significantly increases risks for bone and joint diseases.
Growth rate is indeed directly influenced by energy supply, but a maximal rate of growth is not compatible with optimum growth. Studies have highlighted the damaging effect of excessive energy supply on the growth of large breed puppies. Various groups have looked at the influence of excess energy on skeletal development and found that great Danes fed ad lib had a higher frequency of osteoarticular disorders compared to the same breed fed 66% of the ad lib ration (3,4). One study monitored growth (from 4 weeks to 6 months) in two groups of great Danes, one fed ad lib and the other with a restricted ration (70-80% of the ration); the latter group was itself divided into two, one group being composed of puppies bearing weight loads (15% of their body weight) by means of a belt filled with sand, and the other without weights. After 6 months, the puppies fed ad lib all had skeletal problems, as did the load-bearing puppies (5), thus demonstrating the adverse effect of excess weight during growth. A separate study that followed Labradors from 8 weeks to 2 years of age found that dogs fed 75% of the ad lib intake of matched littermates resulted in a significant decrease in the radiological and clinical signs of hip dysplasia (6).
Practically, food intake of large and giant breed puppies should be closely controlled during growth. Puppies between 12-16 weeks of age should be fed three to four times a day, reducing to twice daily by 8-10 months old. In order to control growth rate, the puppies should be weighed weekly, and the amount fed adjusted accordingly to maintain lean to ideal body condition.
Protein requirements are higher for growth than for maintenance. Quality as well as quantity is important to provide the right balance of amino-acids necessary for the harmonious development and function of all body systems. Following the results of a 1970s study (3) some authors inappropriately concluded that a high protein content in food was unfavorable for correct growth of large breed dogs (3,7). This controversial conclusion quickly became a widespread myth that led many breeders, owners, and veterinarians to recommend limiting dietary protein for large breed puppies. This myth has not been supported by scientific or clinical evidence; one study found no difference in the skeletal development of great Dane puppies raised on diets with the same energy content but containing different protein concentrations (8).
Furthermore, an epidemiological study to identify the risk factors associated with osteochondritis dissecans indicated that so-called premium foods that are higher in protein seem to have a protective effect (9). These observations collectively indicate that protein cannot be implicated as a cause of osteo-articular problems in large and giant breed puppies.
Remember to come back next week for Part 2...
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