American Fancy Rat & Mouse Association

This article is from the WSSF 2007 AFRMA Rat & Mouse Tales news-magazine.

Beginners’ Corner

Nutritional Requirements in Rats

By Karen Robbins

RE: “Mineral & Protein Requirements in Mice” question; what is the rat version?
A According to Laboratory Animal Medicine, the basic protein and fat requirements of rats are listed in Table 1 below. The complete list that includes all nutrient requirements was in the Summer I 1998 Rat & Mouse Tales issue in Beginner’s Corner “Rat Diet” and available on AFRMA’s web site

Table 1
Nutrient Requirements of Ratsa
According to Laboratory Animal Medicine

 Concentration in a dietb
NutrientGrowth, gestation,
or lactation
Protein (as ideal protein)12.00%4.20%
Digestible energy3800.00 kcal/gm3800.00 kcal/gm
a From National Research Council (1978).
b Adequate to support growth, gestation, and lactation; based on 90% dry matter.
c Linoleic acid, 0.6% is required.

As with mice, the different strains affect the amount needed for the rat. There are also different requirements with males vs. females, the age of the rat, the amount of activity, breeding vs. non-breeding stock, the type of cage, temperature of the room where the animals are kept, water used, etc. Also, unlike mice, male rats grow noticeably faster than females, especially during the early weeks. Young from age 3–7 weeks need about twice of what is needed for adult maintenance in energy requirements.

Rats need to eat small amounts several times a day or the stomach will be empty after just 6 hours of no food1.

Pregnant rats need 10–30% more energy and will eat 10–20% more food (Menaker and Navia, 1973) or 20–30% more during the first days of gestation increasing up to 140% by day 16–18 of gestation (Morrison, 1956). If you restrict the diet of pregnant rats, you not only decrease the size and viability of the babies, but she may reabsorb them.

Nursing females need a high protein diet to adequately nurse their young with 24% being required to provide weight gain for the mom. Also, nursing females will consume 2–4 times more energy than non-nursing females and the more babies they are nursing, the more energy they need. They will also lose body fat during the second week of lactation, so it is very important they get the maximum protein and energy required. Research shows nursing females and their young need 18–25% crude protein and 5% fat. Lower protein amounts (17–18%) will give 95% of maximum post-weaning growth but 23% crude protein is necessary for 100% maximum post-weaning growth.

In the book Requirements of Laboratory Animals, it lists estimates of requirements for maintenance, growth, and reproduction in Table 2 (next page). For growing rats or adult rats at maintenance, dietary intake is listed as 15 g/rat/day; during pregnancy: 15 to 20 g/rat/day; during lactation: 30 to 40 g/rat/day. For male maintenance Bricker and Mitchell (1947) suggested a concentration of 7% crude protein in natural-ingredient diets.

Purified diets containing 5 to 10 percent fat have gross energy (GE) values of about 4.0 to 4.5 Mcal/kg (17 to 19 MJ/kg). A diet containing at least 3.6 kcal ME/g (metabolizable energy/gram) (15.0 kJ ME/g) will meet the energy requirement for maintenance and growth if rats are allowed free access to food and the diet is not deficient in other nutrients. Five percent fat is the minimum requirement for all stages of life.

The best way to meet the nutritional requirements in rats (and mice) is to feed one of the pre-formulated laboratory diets supplemented with nutritional treats such as fresh washed veggies and fruits, healthy cereals, etc. (oats, millet, seeded bread, dog biscuits, and some veggies are good for the mice). Karen Robbins *

Laboratory Animal Medicine, Editors: James G. Fox, Bennett J. Cohen, Franklin M. Loew, 1984. Academic Press, Inc., Harcourt Brace Jovanovich, publishers, San Diego, California. ISBN 0-12-263620-1.

Nutrient Requirements of Laboratory Animals, Fourth Revised Edition, 1995, by the National Research Council, ISBN 0-309-05126-6.

1. Vermeulen, J.K., A. de Vries, F. Schlingmann, and R. Remie (1997). “Food deprivation: Common sense or nonsense?” Animal Technology 48(2): 45-54.

Susan B. Roberts and W. A. Coward. “Dietary supplementation increases milk output in the rat.” British Journal of Nutrition (1985), 53(1): 1-9. Cambridge University Press.

Raising Laboratory Animals, A handbook for Biological and Behavioral Research, James Silvan, 1966. The Natural History Press, Garden City, New York. ISBN-10: 0385017006

Table 2
From Nutrient Requirements of Laboratory Animals.

Estimated Nutrient Requirements for Maintenance, Growth,
and Reproduction of Rats
 Amount, per kg diet
NutrientUnitMaintenanceGrowth Repro-
Linoleic acid (n-6)ga6.0a3.0a
Linolenic acid (n-3)gRRR
Proteing50.0b 150.0b150.0
Amino Acidsc
Aromatic AAsdg1.910.210.2
Methionine + cystineeg2.39.89.8
Other (including
A (retinol)jmgg0.70.7
D (cholecalciferol)kmgg0.0250.025
E (RRR--a-tocopherol)lmgg18.018.0
K (phylloquinone)mgg1.01.0
Biotin (d-biotin)mgg0.20.2
Choline (free base)mgg750.0750.0
Folic acidmgg1.01.0
Niacin (nicotinic acid)mgg15.015.0
Thiamin (thiamin-HCl)mmgg4.04.0
B6 (pyridoxine)nmgg6.06.0

NOTE: Nutrient requirements are expressed on an as-fed basis for diets containing 10% moisture and 3.8–4.1 kcal ME/g (16–17 kJ ME/g) and should be adjusted for diets of differing moisture and energy concentrations. Unless otherwise specified, the listed nutrient concentrations represent minimal requirements and do not include a margin of safety. Higher concentrations for many nutrients may be warranted in natural-ingredient diets. R, required but no concentration determined; other long-chain n-3 polyunsaturated fatty acids may substitute for linolenic acid. ND, not determined.
aFemales require only 2 g/kg linoleate for growth. Separate requirements for maintenance have not been determined for linoleate. Requirements presented for growth will meet maintenance requirements.
bEstimates based on highly digestible protein of balanced amino acid composition (e.g., lactalbumin).
cAsparagine, glutamic acid, and proline may be required for very rapid growth (see text).
dPhenylalanine plus tyrosine. Tyrosine may supply up to 50 percent of aromatic acid requirement.
eCystine may supply up to 50% of the methionine plus cystine requirement on a weight basis.
f41.3 g/kg diet as a mixture of glycine, L-alanine, and L-serine.
gSeparate requirements for maintenance have not been determined for minerals and vitamins. Requirements presented for growth will meet maintenance requirements.
hEstimate represents adequate amount, rather than true requirement.
IHigher concentration is required when ingredients that contain phytate (such as soybean meal) are included in the diet.
jEquivalent to 2,300 IU/g. Requirement may also be met by 1.3 mg β-carotene/kg diet. Higher vitamin A concentration is needed under conditions of stress (e.g., surgical recovery).
kEquivalent to 1,000 IU/kg.
lEquivalent to 27 IU/kg. Higher concentration may be required if high-fat diets are fed.
mHigher concentration may be required with low-protein, high-carbohydrate diets.
nEstimate represents adequate amount, rather than true requirements.
Rat with food “Sparkles of Love”
owned by Cathleen
& Roger Russell.
Photo by Cathleen
Chino Hills, CA.

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Updated March 30, 2016