Aging Aging

Dietary Restriction 355Table 1Dietary Composition aComponentPercentageDextrin 45.99RP 101 soy protein 21.00Sucrose 15.00Corn meal 6.00Mineral mix 5.00Vitamin mix 3.30Fiber 3.00DL-Methionine .35Choline chloride .35a This semisynthetic diet mixture is available from Purina Test Diets(Richmond, IN, USA).2. Specific pathogen-free animals: A discussion similar to that of animal facilityconditions required to guard against possible infections can be extended to thehealth status of the animals used in studies, particularly when employing longterm,chronic DR. Although the beneficial effects of DR are known to occur inalmost all laboratory rodents, even when housed in conventional, nonbarrierfacilities, researchers would be better served to use animals having specific pathogen-freestatus (1,9). Experience has taught that prudent animal selection shouldbe made from strains having well-documented records that show the animal’sgrowth patterns, metabolic responses, and pathologic status. This precautionarymeasure gives an added advantage when used in combination with a specificpathogen-free barrier. This is especially true when holding and maintaining animalsfor a lifelong study to investigate aging processes or survival effects, duringwhich time the animals have an increased susceptibility to infection.3. Selection of animal cages: Although not essential, shoebox type, plastic-bottomcages that are fitted with a wire rack are recommended. The reason for choosingthis type of cage over wire-bottom cages relates to food spillage, among otherconsiderations. Food spillage is common to the use of wire-bottom cages and cancreate inaccurate food consumption data. On the other hand, plastic-bottom cageswith raised wire-meshed floor racks allow food spillage recovery, which wouldresult in more accurate data.4. Requirements for a balanced diet: A word of caution is need for the selection ofthe chow used in DR studies. As practiced in the laboratory, DR is imposed ontest animals by a reduction of daily food allotments (usually 40%). It is thereforeof prime importance that the reduced amounts of diet contain all the requirednutrients, particularly those given during the growth period, to avoid any deficiencies.To ensure nutritional sufficiency, it is prudent to choose a well-defined,semisynthetic diet (see Table 1) from a reputable test chow manufacturer. As part