Mouse and Rat Food Regulation

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Mouse and Rat Food Regulation

IACUC Standard Procedure
Effective Date: January 2025

I. General:

This Standard Procedure is for investigators who use food regulation in non-USDA mice and rats for experimental reasons such as studies of homeostatic regulation of energy metabolism or fluid balance, studies of the motivated behaviors and physiologic mediators of hunger or thirst, and studies that regulate food consumption to motivate animals to perform novel or learned tasks. It does not apply to pre surgical fasting prior to anesthesia and surgery or food restriction to animals to maintain optimal, healthy body weight, or infrequent fasting periods of less than 24 hours. As stated in the Guide, “the least restriction that will achieve the scientific objective should be used.” The animals need to be closely monitored to ensure their nutritional needs.

Food restriction paradigms must be carefully designed, and animal welfare closely monitored throughout these studies to ensure that any associated adverse effects such as weight loss are minimized. Food restriction can also lead to the induction of daily torpor, chronic liver damage and associated organ damage, altered immunity, circadian rhythm, behavioral, or hormonal changes. All of these can have profound effects on experimental outcomes and should be carefully considered.

II. Definitions:

Ad libitum: Animals are offered access to a continuous supply of food and can eat as much and as often as they want.

Baseline Body Weight: The average weight prior to beginning the restriction period and/or experimental period. Recommended baseline weight calculation is the average of at least 3 weights measured over a one-week period (5-7 consecutive days).

Removal of food: Food is removed for >24 hours for reasons scientifically justified in the protocol (e.g., prior to sample collection, etc.), after which animals are returned to ad libitum food.

Regulation: A deviation from the standard husbandry practices in the amount or availability of food. It can include Scheduling and Restriction as defined below. Special diets are not inherently considered Regulation.

  • Restriction: The provision of rations such that the total volume of food is strictly monitored and controlled. Restricted feeding typically limits the total volume of food consumed for the purpose of reducing the animal’s weight to a level lower than that expected for an ad libitum fed animal.
  • Scheduling: Limiting of the number of times or length of periods during which the animal has access to food so that the animal consumes a normal portion (as much as desired), but at intervals or durations that differ from standard husbandry practices. This definition only applies if food is removed for a period of greater than 24 hours. Scheduled feeding should not result in a subnormal body weight. For example, rodents are given access to food at least once every 24 hours for at least one hour. After the study session is completed, the rodent is returned to the home cage with ad lib food.

III. Considerations:

  1. The goal for body weight should be no greater than 15% weight loss when compared to the animal’s adult baseline weight or an age- and sex-matched ad lib fed control unless scientifically justified in the IACUC protocol.
  2. In the case of conditioned-response research protocols, the use of highly preferred food as positive reinforcement instead of restriction is recommended. However, exceptions to this recommendation or alternatives may be allowable if scientifically justified.
  3. Efforts should be made to match an animal’s typical eating schedule with circadian variables. Rodents are nocturnal and eat and drink primarily at night. Overnight fasting of mice is not comparable with overnight fasting of humans because the mouse has a nocturnal circadian rhythm and a higher metabolic rate (Jensen et al 2013).
  4. Research staff responsible for monitoring animals on food regulation studies should be trained and competent to evaluate the animal’s condition per their approved protocol.
  5. Food regulation is not recommended in rodents less than 8 weeks of age. Young or growing animals are especially sensitive to food restriction and should be evaluated with a concern for their health and minimum growth requirements.
  6. The IACUC may require documentation of baseline weight and on-study weight for recurring food restriction of <24hr.

IV. Pain Category Classification:

Any animal without access to food >24 hours may need to be listed in Category E. Food deprivation must not exceed 48 hours. Additionally, if scientific needs require a weight loss of > 15%, animals may need to be listed in Category E.

V. Description of Procedure:

  1. Any sort of food regulation must be included in the IACUC protocol, scientifically justified and approved before being implemented.
  2. Cages containing rodents which are on a food regulation study must be labeled in accordance with LARC practices.
  3. Animals should be acclimated to a regulated feeding schedule over a period of time described in the IACUC protocol.
  4. Animals are likely to have the most significant weight fluctuations during acclimation to the food regulation. To ensure that animals are adjusting appropriately during this period, they should be weighed 3x/week.
  5. Any animal that exceeds the % allowable weight loss or displays any clinical signs of distress such lethargy/ruffled hair coat/hunched posture must be temporarily or permanently removed from the study and fed ad libitum.
  6. Assessment and documentation* are required for:
    • Feeding restrictions of any kind; and,
    • Scheduled feeding where animals are without food > 24 hours:
      1. Record daily food consumption for each animal. This can be derived by recording:
        1. Animal’s baseline weight prior to food regulation and/or experimentation
        2. Daily amount food provided and food consumed
      2. Record body weights at least once per week. More frequent body weight recording will be required for greater restrictions. The body weight monitoring plan must be described and approved in the IACUC protocol.
      3. Clinical parameters must be monitored and recorded as described and approved in the IACUC protocol. Examples include,
        1. Activity level (Active versus quiet, lethargic)
        2. Hair coat (Groomed versus ruffled)
        3. Posture (normal versus hunched)
  7. * Recordkeeping:
    1. The Principal Investigator is responsible for the assessment, care and documentation for food-regulated animals.
    2. The lab must record all body weight measurements, , body condition scores, and supportive care. Records must be presented to LARC or IACUC upon request.
    3. Records must include protocol number, principal investigator’s name, date of entry, and pertinent information.

VI. Literature Search Words Required:

Key WordsSearch
Sites		Years
Covered
Mouse, Food, Deprivation, Regulation, Guidelines, Restriction, WelfarePub
Med		1970-2020

Literature search was performed for development of this Standard Procedure in June 2020.

VII. References:

  1. Bachmanov, A. A., D.R. Reed, G. K. Beauchamp, and M. G. Tordoff. "Food Intake, Water Intake, and Drinking Spout Side Preference of 28 Mouse Strains." Behav Genet 32.6 (2002): 435-43.
  2. Bachmanov, A.A., G.K. Beauchamp, and M.G. Tordoff. "Voluntary Consumption of NaCl, KCl, CaCl2 and NH4Cl Solutions by 28 Mouse Strains." Behav Genet 32.6 (2002): 445-57.
  3. Bekkevold, C.M., K.L. Robertson, M.K. Reinhard, A.H. Battles, and N.E. Rowland. "Dehydration Parameters and Standards for Laboratory Mice." JAALAS 52.3 (2013): 233-39.
  4. Boston University Food Regulation and Restriction in Rodents Policy, Review dated: 2019.
  5. Brown University IACUC Policy on Food and Fluid Regulation in Rodents, Review Date: June 2, 2017.
  6. Goodrick, C. L. et al. (1982). Effects of intermittent feeding upon growth and life span in rats. Gerontology 28(4), 233–241.
  7. Goodrick, C. L. et al. (1983). Effects of intermittent feeding upon growth, activity, and lifespan in rats allowed voluntary exercise. Exp. Aging. Res. Fall 9(3), 203–209.
  8. Goodrick, C. L. et al. (1990). Effects of intermittent feeding upon body weight and lifespan in inbred mice: Interaction of genotype and age. Mech Ageing Dev. July 55(1):69-87.
  9. Guidelines for the Care and Use of Mammals in Neuroscience and Behavioral Research. ILAR. NRC. 2002. Food and Fluid Regulation. 49–61.
  10. Hickman, D.L., and M. Swan. "Use of a Body Condition Score Technique to Assess Health Status in a Rat Model of Polycystic Kidney Disease." JAALAS 49.2 (2010): 155-59.
  11. MIT CAC Guidelines on Food and Water Restriction in Rodents, 2007.
  12. National Institute of Aging: Guidelines for Caloric Restriction in Rodents.
  13. National Research Council. “Food and Fluid Regulation.” Guide for the Care and Use of Laboratory Animals. 8th ed. Washington, D.C.: The National Academies Press. (2011): 30-31.
  14. National Research Council. Guide for the Care and Use of Laboratory Animals: Eighth Edition. Washington, DC: The National Academies Press, 2011. Pp 30-31.
  15. Purina Mills Lab Diets. http://www.labdiet.com/
  16. Rowland, Neil E. Food or Fluid Restriction in Common Laboratory Animals: Balancing Welfare Considerations with Scientific Inquiry. Comparative Medicine, 57(2), April 2007. (Highly recommended).
  17. Schmidt-Nielsen, Knut. Scaling. Why Is Animal Size so Important? Cambridge University Press.1984.
  18. The Guide for the Care and Use of Laboratory Animals. ILAR. NRC. p. 12. 1996.
  19. Toth, Linda A. and Gardiner, Thomas W. Food and Water Restriction Protocols: Physiological and Behavioral Considerations. Contemp. Topics 39(6), Nov. 2000.
  20. Ullman-Culleré, M.H., and C.J. Foltz. "Body Condition Scoring: A Rapid and Accurate Method for Assessing Health Status in Mice." Laboratory Animal Science 49.3 (1999): 319-23.
  21. University of Michigan UCUCA. Policy on Food and Water Restriction or Manipulation in Laboratory Animals. 2007.
  22. Wolfle, Thomas. 50 years of the Institute for Laboratory Animal Research (ILAR). (2003): 324-337.