stocks, and 3 monogamously mated outbred stocks. Differences in the percentage of sterile matings, litter size, and preweaning mortality were evident among major inbred strains such as Brown Norway, Fischer 344, Osborne-Mendel, Sprague-Dawley, and Wistar (Table 2-1). Outbred strains tended to have higher reproductive performance (Table 2-1). Thus the expected reproductive performance of rats in experimental studies may vary according to strain and system of breeding.

Although the nutrient requirements of the laboratory rat are better known than those of other laboratory animals, there can be considerable disparity in estimated requirements as a consequence of the criteria used (Baker, 1986). For example, the amounts of nutrients required to sustain maximum growth of young rats may be different from the

amounts needed to maintain tissue concentrations or to maximize functional measures such as enzyme activities. Moreover, nutrient requirements are not static; they change according to developmental state, reproductive activity, and age. There is also evidence of differences in requirements between males and females as well as among various inbred and outbred strains. The nutrient requirements listed in this chapter represent average values, but they may not suffice in all circumstances. There is a need for further research that will identify the sources of variation in nutrient requirements.

Recommended nutrient concentrations in this report have not been increased to allow a margin of safety for variation in dietary ingredients or for differences among rats. The data on which requirements are based were reported from many different laboratories that used various colony management practices. One may assume that the recommendations are adequate for rats in most laboratory conditions, but particular experimental protocols such as maintenance of germ-free colonies or testing of experimental drugs (see Chapter 1) may alter the requirements for one or more nutrients. In some cases sufficient data were available to differentiate the nutrient requirements for adult maintenance from those for growing, pregnant, or lactating rats; hence, estimates of requirements are provided for maintenance, growth, and reproduction (Table 2-2). If data available were insufficient to determine requirements, adequate concentrations are reported on the basis of long-term feeding. If cited papers provided nutrient intakes per day but did not specify dietary concentrations, the values have been converted to dietary content by assuming a dietary intake of 15 g/rat/day for growing rats or adult rats at maintenance, 15 to 20 g/rat/day during pregnancy, and 30 to 40 g/rat/day during lactation.

Front Matter (R1-R14)

Overview (1-2)

1 General Considerations for Feeding and Diet Formulation (3-10)

2 Nutrient Requirements of the Laboratory Rat (11-79)

3 Nutrient Requirements of the Mouse (80-102)

4 Nutrient Requirements of the Guinea Pig (103-124)

5 Nutrient Requirements of the Hamster (125-139)

6 Nutrient Requirements of the Gerbil (140-143)

7 Nutrient Requirements of the Vole (144-148)

Appendix (149-153)

Authors (154-156)

Index (157-176)