CHAPTER 8 Nutritional Requirements and Feeding of Growing Puppies and Kittens
Nutrition during the first year of life can greatly influence the longevity and health of puppies and kittens. Inadequate protein and energy intake can decrease growth rate, inhibit neural myelination and neurotransmission, decrease brain growth, and inhibit cognitive function. Many neonatal deaths result from inadequate nutritional intake or the inability of the neonate to adequately digest and absorb nutrients as a result of the immature digestive system. At birth, the gastrointestinal (GI) tract must transition from processing amniotic fluid to digesting milk. The release of hormones and digestive enzymes and the activation of secretion, motility, and absorption are adaptations that begin shortly after birth. These changes are critical to allow the GI tract to perform required functions.
The intestinal mass of puppies increases in the first 24 hours. Pancreatic lipase production increases over the first 3 weeks as the amount of milk fat increases. The increase in lipase production increases the thickness of the GI wall and facilitates the passage of solids. Intestinal growth is decreased if milk replacer is fed in place of colostrum, possibly caused by missing hormones, fat, or other colostral components.
Neonates have decreased pancreatic digestive enzymes, which permits intestinal absorption of immunoglobulins from the colostrum. The neonatal pancreas does not begin to produce amylase until after 21 days of age. However, canine milk contains the digestive enzyme amylase, which helps digest milk sugars in the neonatal GI tract. Digestive enzymes are produced in response to consumption of solid food. Therefore consuming solid food is important to facilitate the development of normal GI tract function in the young dog and cat.
GI motility, relative to older puppies and kittens, is reduced in neonates less than 30 days old. This must be taken into consideration when a neonate requires supplemental feeding either by bottle or orogastric tube. Therefore small amounts should be fed frequently to decrease the possibility of regurgitation and aspiration.
Milk consists of lipids, sugars, minerals, and minor constituents. For the first 24 hours after parturition, “immature milk” is produced, which slowly matures over the next week. The immature milk, or colostrum, is rich in proteins, immunoglobulins, energy, nutrients, and growth factors that stimulate GI tract development. The energy in colostrum is 95% digestible. Species with a small body size, such as dogs and cats, produce milk higher in energy density to compensate for small gastric capacity. Puppies and kittens that do not receive colostrum are more susceptible to infection until about 35 days of age. Levels of calcium, phosphorus, and magnesium are initially high for 2 to 3 days and then decrease as the milk matures.
A healthy mother who is well-nourished should be able to provide complete nutrition for a puppy or kitten for their first 4 weeks. A healthy puppy or kitten will nurse vigorously several times a day and gain weight on a daily basis. A malnourished puppy or kitten will fail to gain weight, constantly cry, and become inactive (see Chapter 11). More neonates die from improper husbandry and nutrition than disease. Birth weight is the single most important predictor of neonate survival. Average birth weight for toy, medium, large, and giant breed dogs can be found in Box 8-1.
Formulated puppy and kitten milk replacer is available commercially. Both powder and liquid forms are available. Powdered formula lasts longer, since the unused powder can be frozen for 6 months. Once powdered formula has been reconstituted, contents should be used within 48 hours, provided the unused portion is refrigerated in a glass container. Liquid milk replacer should be used within 48 hours once the can is opened, provided the unused portion is refrigerated. Formulated milk replacer is superior to homemade versions because commercial products generally provide the correct balance of protein, fat, carbohydrates, vitamins, and minerals needed for growing neonates. Ingredients and caloric density of the puppy milk replacer can vary with manufacturer. The label recommendations should be for the product being administered.
Milk replacer is made from bovine milk and is lower in protein, calories, fat, calcium, phosphorus, and carbohydrates. This may explain the decreased growth rate of orphan puppies and kittens, even though the caloric intake may be equivalent. Bovine milk is higher in lactose than either canine or feline milk, which can cause diarrhea in puppies and kittens fed milk replacer. It is advised to dilute milk replacer 25% to 50% with water or a balanced electrolyte solution for the first 2 days of feeding to minimize the occurrence of diarrhea.
If commercial milk replacer is temporarily unavailable, an emergency formula may be used (Box 8-2). This emergency formula is strictly for emergencies and should be replaced with a commercial milk formula as soon as possible.
By the time the neonate is 3 to 4 weeks old, dry food can be mixed with water and/or formula in a 1 : 3 ratio to form a gruel. If canned food is preferred, a 2 : 1 ratio can be made. Pediatric patients receive hydration from the milk or the milk replacer, but water intake will increase once offered. Drinking water should be offered at 5 weeks. By 6 weeks of age, 50% of the pediatric patient’s diet should be from unmixed puppy or kitten food. Puppies and kittens can be totally weaned from the dams’ milk at approximately 6 to 8 weeks. Early weaning (defined as completely removed from their mother) is discouraged, since it can lead to malnutrition, stress-related diseases, diminished social skills, and behavioral problems. However, nutritional weaning can start as early as weeks of age. The advantages of this earlier nutritional weaning in the opinion of some are preventing debilitation of the dam nursing a large litter and allowing the transitioning process of the GI tract to solid food while still under the protection of colostral antibodies. From the time of weaning until 6 months old (9 months in large-breed dogs), it is advised to feed juveniles three times a day and more frequently for smaller and toy breeds. Thereafter dogs and cats should be fed twice daily on a regular schedule.
The Association of American Feed Control Officials (AAFCO) was established in response to the increasing number of pet food diets available on the market, some of which did not meet the specific nutritional needs of animals. The AAFCO is made up of a variety of individuals and is not regulated or managed by any pet food manufacturer. Any foods that are recommended by veterinarians should meet the expectations and testing of AAFCO. A label that reads “complete and balanced” must either meet a nutrient profile or pass a feeding trial. To be classified as “safe,” the food must meet all nutrient minimum and maximum ranges that have been established by the AAFCO as being safe.
To compare diets, food must be looked at on a “dry matter (DM) basis.” The AAFCO’s definition of DM basis is the level of nutrients contained in a food. A “guaranteed analysis,” or “as fed basis,” must be converted to DM to effectively compare diets. For example, a canned diet contains approximately 75% moisture, whereas a dry diet contains approximately 10% moisture. To effectively compare the two products, the moisture content must be removed. Ingredients are listed on the label by weight and can include moisture. Therefore some products may list chicken as their main ingredient, but it may only weigh more than the corn or wheat products that follow because of its moisture content.
The most commonly used unit of measurement is the kilocalorie (kcal), defined as the amount of heat necessary to raise the temperature of 1 kilogram (kg) of water by 1 degree Celsius. Calories are used to maintain physical activity, digestion, growth, and basal metabolism. Most foods are recommended in kilocalorie/8 oz cup of dry food or kilocalorie/can. Puppies and kittens require a larger amount of energy early in life, which decreases as they age. It is important to follow the feeding recommendations established by the pet food manufacturer, since diets vary by company, as well as within a specific product line. The AAFCO nutrient requirements for puppies and kittens are listed in Tables 8-1 and 8-2, respectively.