Monday, January 26, 2009

Pet Nutrition: Requirements and related diseases Part 1 Water & Energy

Dogs are a biologically diverse species, with normal body weight of anywhere between 2 to 175 lbs. Normal birth weight of puppies depends on breed type and is on average 4 to 20 oz. During the first two weeks a puppy’s life is spent eating, seeking warmth, and sleeping. External food sources beyond mother’s milk is rarely needed unless the mother cannot produce enough milk or the puppy is orphaned. In these cases, the puppy must be hand reared. Growth rates of puppies are rapid for the first 5 mo; in this period, pups gain an average of 2 to 4 g/day/kg of their anticipated adult weight. The growth rate begins to reach its peak and plateau after 6 months. Growth may be completed by 9 to 12 months of age in small breeds and by 12 to 18 months in large breeds. By comparison, the average mature body weight of domestic cats is 7 lbs for males or toms and 6 lbs for females or queens. Normal birth weight of kittens is 3 to 4 oz. The growth rate is exceptionally rapid for the first 3 to 4 months and kittens gain 50 to 100 g/wk. The growth rate begins to plateau at 150 to 160 days of age and growth is completed within 200 to 220 days.

Dogs and cats require specific dietary nutrient concentrations based on their life stage. The Association of American Feed Control Officials (AAFCO) publishes dog and cat nutrient profiles for growth, maintenance, and reproduction. These are based in part on the 1974 and 1985 National Research Council (NRC) nutrient requirements for these species (Table: AAFCO Nutrient Requirements for Dogs and Table: AAFCO Nutrient Requirements for Cats). Updated NRC requirements have recently been established and will be published soon. These provide a comprehensive review of the nutrient requirements for various life stages and may be used by AAFCO to modify their profiles.

In developed countries, nutritional diseases are rarely seen in dogs and cats, but only if and especially when they are fed good quality commercial rations or nutritionally balanced homemade diets. Dog or cat foods or homemade diets derived from a single food item are inadequate. For example, feeding predominately meat or even an exclusive hamburger and rice diet to dogs can induce calcium deficiency and secondary hypoparathyroidism. Feeding raw, freshwater fish to cats can induce a thiamine deficiency. Feeding liver can induce a vitamin A toxicity in both dogs and cats. Malnutrition has been seen in dogs and cats fed “natural,” “organic,” or “vegetarian” diets produced by owners with good intentions, and most published recipes have been only crudely balanced by using calculated nutrient averages. Because the palatability, digestibility, and safety of these recipes have not been adequately or scientifically tested, it is difficult to characterize all of these homemade diets. Generally, most formulations contain excessive protein and phosphorus and are deficient in calcium, vitamin E, and micro minerals such as copper, zinc, and potassium. Also, the energy density of these diets may be unbalanced relative to the other nutrients. Commonly used meat and carbohydrate ingredients contain more phosphorus than calcium. Homemade feline diets that are not actually deficient in fat or energy usually contain a vegetable oil that cats do not find palatable; therefore, less food is eaten causing a calorie deficiency. Rarely are homemade diets balanced for micro minerals or vitamins.

Some nutritional diseases are seen secondary to other pathologic conditions or anorexia, or both. Owner neglect is also a frequent contributing factor in malnutrition.

Clean fresh water should be available at all times. Multiple water sources encourage consumption. Several approaches have been used to estimate daily water needs. In a thermo neutral environment, most mammalian species need about 44 to 66 mL/kg body wt. Another approach takes into account the fact that water needs appear to be highly associated with the amount of food consumed. In this case, daily maintenance fluid requirements in mL should equal the animal’s maintenance energy requirement in kcal of metabolizable energy (ME). A third technique sets daily water intake as 2 to 3 times the dietary dry matter intake. When provided ample amounts of water, healthy animals can effectively self regulate their intake. Water deficiency can be seen as a result of poor husbandry or disease. Dehydration is a serious problem in disorders of the GI, respiratory, and urinary systems. If dehydration has occurred, here is what your vet most likely is going to do: During anorexia or increased fluid losses, for dogs a 2 to 5% or for cats a 1 to 2% glucose and electrolyte solution should be administered to adult dogs or cats at 60 to 80 mL/kg body wt/day or 80 to 100 mL/kg in puppies and kittens to maintain normal fluid balance.

The most useful measure of energy for nutritional purposes is ME, which is defined as that portion of the total energy of a diet that is retained within the body. It is typically measured in calories or joules. Dogs and cats require sufficient energy to allow for optimal use of proteins and to maintain optimal body weight and condition through growth, maintenance, activity, pregnancy, and lactation. Of the 6 nutrient groups, only protein, fat, and carbohydrate provide energy, whereas vitamins, minerals, and water do not. Dogs and cats not consuming sufficient calories lose body weight and condition. Energy requirements for dogs and cats are not a linear function of body weight. Recent evidence indicates that pets maintained in households require fewer calories per day compared with dogs held in kennels, but considerable variability exists. Breed differences also affect caloric needs independent of body size. For example, Newfoundlands appear to require fewer calories/day than Great Danes. Other factors that determine daily energy needs include activity level, life stage, percent lean body mass, age, and environment. Even when specific formulae are used, any given animal may require up to 30% more or less of the calculated amount. Consequently, general recommendations may need to be modified within this 30% range, and body condition scoring should be regularly performed. In view of this variability, energy requirements for dogs are about 65 kcal/kg body wt for kennel or active adult dogs, about 50 kcal/kg body wt for inactive adults, about 120 kcal/kg for growing puppies, about 200 kcal/kg for lactating bitches, depending on litter size, and about 450 kcal/kg for heavily worked dogs. For cats, energy requirements are around 70 kcal/kg for lean adults, about 200 kcal/kg for growing kittens and 150 kcal/kg for lactating queens.
The precise ME values for many dog food ingredients have not been experimentally determined and are often estimated using those for other monogastric species (such as pigs) or calculated using Atwater physiologic fuel values modified for use with typical dog food ingredients. The precise ME values for many cat foods are not known, although it is believed that the factors used for dogs may apply. The modified Atwater ME values for dogs are 3.5 kcal/g for carbohydrate or protein and 8.5 kcal/g of fat. The impact of various environmental temperatures is described in the recent NRC publication on nutrient requirements of dogs and cats and has been documented under certain conditions. For example, energy requirements increased from 120 to 205 kcal/kg in Huskies as ambient temperatures decreased from 14°C in summer to -20°C in winter. Effects of environmental temperature are not well characterized in cats because most of the research has been done under thermo neutral (68 to 72°F) conditions. However, unacclimatized adult cats increased their daily caloric intakes by nearly two fold when environmental temperatures of 23°C and 0°C were studied.
Source: Merck Veterinary Manual
Soon to follow: Part 2 Protein, Fats, Carbohydrates & Fiber

1 comment:

Kevin said...

Very nice tips. Thanks for sharing!
Puppy Growth Rate