Diets For Germfree Animals

Diets for GF animals are nowadays well established. They fall into three categories: natural ingredient diets fortified for the losses that occur during sterilization (Table 46.1); diets with minimal antigenicity, used mainly for immunological studies; and the chemically defined antigen-free diets, used for immunological and other studies where absolute definition of environment and dietary intake is required, again used mainly in immunology. For more defined work in the first category, diets based on rice starch, a well-defined source of protein like casein or soy protein, some fat, generally corn oil, and well-defined vitamin and mineral mixes have been developed (Table 46.2) and are commercially available. Diets of minimal antigenicity have been developed for the study of the very early phases of immune response in young colostrum-deprived gnotobiotic (GN) piglets (Kim and Watson, 1969).

Extreme definition was obtained with the development of the GF mouse reared on a totally chemically

TABLE 46.1 Composition of natural ingredient diet l-485 Ingredients g/kg Nutrient composition, %

Ground corn 590 Protein 20.0

Soy bean meal, 50% CPa 300 Fat 5.3

Alfalfa meal, 17% CP 35 Fiber 3.0

Corn oil 30 Ash 5.5

Iodized NaCl 10 Moisture 11.2

Dicalcium phosphate 10 Nitrogen-free material 55.0

Calcium carbonate 5

Lysine (feed grade) 5 Gross energy 3.9 Kcal/g

Methionine (feed grade) 5

Vitamin and mineral mixes 0.25b

BTH 0.125

"Crude protein.

bKellogg, T. F., and Wostmann, B. S. (1969). Stock diet for colony production of germfree rats and mice. Lab. Anim. Care 17, 589.

defined, water-soluble antigen-free diet (CD diet), consisting of dextrose, amino acids, water-soluble vitamins, minerals, and a fat supplement, sterilized by ultrafiltration (Table 46.3) (Pleasants et al., 1986). This successful colony was started with inbred GF BALB/cAnN mice obtained from the GF colony maintained at the University of Wisconsin. Pregnant GF mice of this colony originally were fed natural ingredient diet L-485 (Table 46.1), then transferred to another isolator and fed CD diet. Their offspring, never having been in contact with other than the CD diet, were housed in plastic isolators in shoebox-type mouse cages, with lids modified to hold the inverted

TABLE 46.2 Composition of casein-starch diet L-488F, fortified with cholesterol g/100g

TABLE 46.2 Composition of casein-starch diet L-488F, fortified with cholesterol g/100g

Casein

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