What Do Rodents Eat? A Comprehensive Guide to Their Diet
Note that alterations of these formulations may be appropriate to accommodate changes in ingredient availability or nutrient composition. Parallel grooves, where a rat’s incisor teeth have bitten into the food material, are usually visible. Rat tunnels in the soil have an entrance diameter of 30-40mm, about twice that created by mice or voles. The pellets are cylindrical in shape with rounded ends and are about 15mm long and 5mm wide when fresh, again about twice the size of mice or vole droppings. Adult rats are about 21cm long with relatively hairless tails that add another 18cm to the animal’s length.
The growth rates published by Poiley (1972) for 38 stocks and strains of mice show an approximately twofold difference between the slowest and fastest growing mice. Growth statistics for five stocks and strains representing this range of mouse genotype are shown in Table 3-1. This difference in growth suggests a marked difference in nutrient requirements among mouse genotypes. Considering this large variation in growth rates, expected or acceptable growth rates used as standards should come only from those individuals responsible for maintaining the breeding colony that provides a given genotype. Two natural-ingredient diets containing 3.6 and 4.9 g Na/kg diet (Knapka et al., 1974) and a purified diet containing 3.9 g Na/kg diet (Bell and Hurley, 1973) are known to support good growth and reproduction. However, the estimated requirement for sodium and chloride is 0.5 g Na/kg diet and 0.5 g Cl/kg diet, which is identical to that estimated for rats.
No information is available about the requirements for pregnancy and lactation. High dietary concentrations of zinc, cadmium, and ascorbic acid may increase the dietary requirement for copper (Davis and Mertz, 1987). The estimated requirement for a single amino acid depends on the amounts of other amino acids in the diet and the rate of growth. With the exception of D-lysine (Friedman and Gumbmann, 1981) and probably D-threonine, the L-indispensable amino acid requirement may be met, in part, by D-amino acids.
Mice were able to adapt to a low-iodine intake by maintaining normal concentrations of iodine in the thyroids. When they were challenged with a mycotoxin, however, the iodine concentration decreased. There was no effect of the toxin on thyroid iodine content in mice fed 150 µg I/kg diet. • Wild mice and rats will eat just about anything, including fruits, vegetables, seeds, insects, eggs, and even small animals.• In captivity, pet mice and rats must have a diet rich in protein and fiber. Commercially prepared foods are available specifically designed for these animals.
Beard and Pomerene (1929) found that mice fed vitamin D-deficient diets developed signs of rickets within 7 to 14 days. Rickets spontaneously healed between days 20 to 27 without vitamin D supplementation, but osteoporosis was present in many of the animals after healing. Delorme et al. (1983) found that both the 10,000 and 25,000 molecular weight kidney vitamin D-dependent calcium binding proteins were reduced to about one-third the normal concentrations in vitamin D-deficient Swiss mice. In contrast, milk production and the calcium content of the milk were normal in CD-1 mice fed a vitamin D-deficient diet (Allen, 1984). Based on these limited results, the estimated minimal requirement for both immature and adult mice is set at 6 mg Cu/kg diet.
When fed a natural-ingredient diet that contained 13,371 IU/kg (roughly 14 µmol/kg), A/J mice were found to accumulate vitamin A reserves in their livers as they increased in age from 9 to 216 days old (Sundboom and Olson, 1984). However, 644-day-old A/J mice were found to have about one-half the liver vitamin A stores observed in mice 216 days old. The rate of depletion of tissue linoleate is biphasic (Tove and Smith, 1959) with the most rapid loss occurring when linoleate comprised more than 20 percent of the depot fat. Also, female and immature male mice lose linoleate more quickly than mature males during the slower, second phase of depletion.
The n-6 stores of the mice were unknown; it is likely that the requirement is higher in the young growing mouse. Mice (Mus musculus) have been used extensively as animal models for biomedical research in genetics, oncology, toxicology, and immunology as well as cell and developmental biology. Morse (1978) wrote a detailed history of the development of the mouse as a model for biomedical research. Estimating the quantitative nutrient requirements for mice is particularly challenging because of the large genetic variation within the species and the different criteria used to assess nutritional adequacy of diets. Research to determine nutrient requirements for reproduction, lactation, and maintenance of mice has received relatively little attention.
Differences in growth potential among strains have been observed (see Table 3-6). Mice of the C57BL/6 strain gained 0.44 g/day, while CD-1 mice gained 0.68 g/day (Olejer et al., 1982); and Swiss-Webster mice gained 0.4 g/day, while the Rockland strain gained 0.78 g/day (Maddy and Elvehjem, 1949). Few studies have focused on estimating amino acid requirements of mice (John and Bell, 1976; Bell and John, 1981).
Results of studies on the specific requirements for reproduction and lactation have not been reported, but Mirone and Cerecedo (1947) found that 20 mg/kg diet were adequate. The purified diet (American Institute of Nutrition, 1977) containing 6 mg thiamin-HCl/kg diet has been used in numerous mouse colonies resulting in normal growth and reproduction. In the absence of more definitive data the concentration of 5 mg thiamin-HCl/kg diet that was the estimated requirement in the previous issue of this report (National Research Council, 1978) is being retained. Sandza and Cerecedo (1941) found that subcutaneous injections of 63 nmol Ca-d-pantothenate 6 days each week would maintain an optimal growth rate in albino mice.
Based on these results, the estimated required potassium concentration for mice is 2.0 g K/kg diet. A decrease in growth was noted when the dietary fat content exceeded 40 percent. Fenton and Carr (1951) demonstrated that the effect of dietary fat concentration on weight gain of mature mice depended on the strain. Strains A and C3H Check this for Doeat.top What do fish eat had higher rates of gain when dietary fat was increased from 5 to 47 percent, while strains C57 and I showed no further increases in weight gain when the fat content of the diet was increased to more than 15 percent. The idea of rodents as game or livestock is not just a question of cultural or culinary traditions, however.
If rapid depletion is desired, it is necessary to use the pups from a pregnant female fed a vitamin A-deficient diet from about day 10 of gestation; this will produce very low vitamin A stores in the pups (Smith, 1990). Young mice weaned from dams fed a standard diet may require up to 1 year to show overt signs of deficiency. Santhanam et al. (1987) have explored methods to slowly produce vitamin A deficiency in mice. Both BALB/c and Swiss mice eventually developed deficiency signs when fed a cereal grain-based diet calculated to contain 1,200 IU vitamin A/kg (roughly equivalent to 1.2 µmol retinol/kg diet).
The teratogenic effects were much more severe in the fast-growing ICR and C57BL/6N strains than in the slower growing A/Jax mice. The other signs of deficiency include alopecia, achromotrichia, and growth failure, as well as decreased reproduction and lactation efficiency (Nielsen and Black, 1944). Vitamin K has not been considered essential for mice reared under conventional conditions because of the substantial contribution from coprophagy. However, with the increased use of specific-pathogen-free animals for research, this is probably no longer true. Both specific-pathogen-free CF1 mice (Fritz et al., 1968) and germ-free ICR/JCL mice (Komai et al., 1987) were reported to die quickly from hemorrhagic diathesis when fed vitamin K-free diets. Addition of 16 µmol menadione/kg to the diet prevented hemorrhaging problems in the specific-pathogen-free mice.
