Approximately 30% of puppy mortality occurs during the first 14 days of life[1]. Many of these deaths result from inadequate nutrition or the inability of the puppy to adequately digest and absorb nutrients because of its immature digestive system[2]. Nutrition, during both prenatal and postnatal development and in the first year of life, can influence its longevity and health later in life[3, 4]. Research knowledge to the changes that occur in the puppy's immature gastrointestinal tract and the nutritional demands of puppyhood helps build diets that will have a positive influence on the vitality and health of the growing puppy.

The development of the gastrointestinal tract is key in establishing health. At birth this organ system undergoes perhaps the most drastic changes in function of any organ system except the lungs. During this time, the gastrointestinal tract must take over from the placenta the huge task of transferring nutrients from the outside world to the neonatal circulation. The normal, healthy gastrointestinal tract must be capable of digestion and absorption of mother's milk--it's primary substrate for energy and other nutrients. As the puppy's gastrointestinal tract matures, it is challenged by an ever-increasing volume of milk received from its mother. At weaning, it is a critical transition from liquid to dry food whereby milk intake and nutrient intake from milk decreases and solid food intake and reliance upon solid food increases. As such, the puppy's developing gastrointestinal tract must undergo considerable change and be prepared to facilitate the digestive and absorptive functions required for this change in its diet.

In concert with the changes in the maturation of the puppy's gastrointestinal tract, its nutritional needs change as well. Given that adult dog body size of different breeds can range by nearly 100-fold, it is not surprising that there can be nutritional differences depending on breed size. Breed size can affect energy, protein, and calcium requirements as well as calorie content of the diet. These and other factors will be explored during the presentation.

Understanding the developmental needs of the puppy help nutritionists and veterinarians develop and recommend diets that best meet the needs and digestive abilities of growing puppies during each stage of development.