20 September, 2019

Incorporating Test Compounds in Lab Animal Diets

By Tina Herfel

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A convenient approach to dosing research animals is adding compound(s) to diet. Envigo offers a service that allows researchers to add their compound(s) of interest to animal diets. When adding a compound to a diet, there are some important considerations regarding formulation, compound stability and safety. An Envigo nutritionist can assist you through this process by contacting us at askanutritionist@envigo.com to discuss. Some frequently asked questions about this process are discussed below.

Why do researchers add compounds to diets?

Diet dosing is a well-established practice that can be used with a variety of compounds and diet types. Diet dosing allows researchers to easily dose large numbers of animals and may improve welfare compared to other oral dosing techniques by eliminating the need for animal handling or special equipment. To treat your animals simply place the diet on the cage top feeding grid.

What types of compounds can be added to a research diet?

Generally, if the stability or activity of the compound is not compromised during manufacture or further processing such as irradiation, an ingredient can be added to an Envigo diet. Envigo stocks several common additives such as doxycycline, tamoxifen and cuprizone, but also allows researchers to provide compounds. Medications or compounds supplied by an investigator are referred to as “customer supplied ingredients” or “customer reserves,” and they can be added to most diets.

What information is needed to have a compound added to a research diet?

When working with a nutritionist to design your compound added diet you will need to provide some general information:

  1. If you will be supplying the compound we will ask for safety and storage information
  2. What diet you would like the compound added to
  3. How much of the compound you want in the diet on a mg/kg of diet (ppm) or percentage basis

What safety information will I need to provide regarding my compound?

If supplying your compound, you will be asked to provide the safety datasheet. A safety datasheet may not be available for some novel compounds. If not available, you may be asked to complete an alternative form outlining the safe handling of you ingredient. We will also ask how you would like your compound stored.

Food products generally will not require safety information, although information about nutrient content, reason for use, etc. is helpful in the design of diets.

How much compound will I need to provide for the production of my diet?

For diets containing customer supplied ingredients, we ask that you provide enough compound for the quantity of diet purchased plus 1 – 2 kg of additional diet. The Teklad minimum order quantity is 3 kg and you may increase your order size in 1 kg increments. If your compound is limited, discuss with our nutrition team options for creating a smaller diet batch.

What diet can I add my compound to?

Compounds can be added to standard natural ingredient diet (chow) and also purified diets. When adding compound to a natural ingredient diet this typically involves grinding the standard diet pellets into a powder, mixing in your compound and then pelleting. Your vivarium should be able to provide you with the manufacturer and product code typically fed to your colony. You will need to provide this information to the Envigo nutrition staff to design your diet. For compound additions, Envigo stocks Teklad diets and some diets made by other companies.

Compounds can also be added to purified diets. For example, a statin could be added to a Western high fat diet or resveratrol to a diet formulated to induce obesity. If the custom diet is from Teklad, simply share the catalog number with the nutritionist. If the diet was produced by another company, provide a description and preferably the complete diet formula.

How do I asses the suitability of the inclusion of my compound in a pelleted diet?

Depending on the diet formulation, pelleting may involve the addition of water and/or heat. Water is often added as a pelleting aid. Pellets are formed under pressure but no external heat is applied. After pelleting, diets are often dried by heating the diet, although some formulations may be air dried. It will be your responsibility to determine the suitability of the compound for inclusion into a pelleted diet. A nutritionist can provide more detailed information about this process.

Post-pelleting, you may request that your diet to be irradiated (a form of diet sterilization). Envigo’s diet irradiation dose range is 20 - 50 kGy. We defer to you to determine the suitability of your customer supplied compound(s) for irradiation.

How do I calculate a diet dose from a target daily dose?

Formulating an appropriate dietary dose is critical to the design of an experiment. To calculate a diet dose one will need to know:

  • The target daily dose, mg compound/kg of body weight/day (DD)
  • Animal body weight, kg body weight (BW)
  • Daily food intake, g diet/day (FI)

The diet dose can then be calculated using this formula:

Diet dose (mg compound/kg of diet) = (DD * BW)/FI * 1000

How do I calculate a diet dose based on a human dose or other animal model?

If you need to formulate a diet dose based on a different animal model or human dose, you may want to consider scaling the dose based on allometry. There are different equations for allometric dosing. A simple method determines dosage based on metabolic rate by adjusting body weight to the 0.75 power. This represents the relationship between body weight and metabolism of adult animals. Another possible method extrapolates animal doses from human doses by adjusting for body surface area (BSA).

If your goal is to mimic the nutrient intake of a human population or dietary pattern, you may want to design your diet to provide the same amount of test ingredient per calorie as a typical human diet.

References that may be helpful in determining a diet dose for your test compound:

Allometric Scaling:

Center for Drug Evaluation and Research, C. for B., & Evaluation and Research. (2005). Estimating the safe starting dose in clinical trials for therapeutics in adult healthy volunteers. Retrieved from http://www.fda.gov/cder/guidance/index.htm

Hawk, C. T., Leary, S. L., & Morris, T. H. (2005). Formulary for laboratory animals. (E. C. of L. A. M. American College of Laboratory Animal Medicine, Ed.) (3rd ed.). Ames, Iowa: Blackwell Publishing.

Reagan-Shaw, S., Nihal, M., and Ahmad, N. (2008). Dose translation from animal to human studies revisited. FASEB J 22, 659-661. https://www.ncbi.nlm.nih.gov/pubmed/17942826

Dietary Pattern:

Hintze, K. J., Benninghoff, A. D., & Ward, R. E. (2012). Formulation of the Total Western Diet (TWD) as a basal diet for rodent cancer studies. Journal of agricultural and food chemistry, 60(27), 6736-6742. https://www.ncbi.nlm.nih.gov/pubmed/22224871

How do I contact an Envigo nutritionist to begin the process of adding a test compound to an animal diet?

Please contact us at askanutritionist@envigo.com or 1.800.483.5523 for consultation regarding adding a test compound to your research animal diet. A phone call or an email exchange with one of our staff will augment the information that you gather from our web site or published literature, and you are more likely to receive a diet that best meets your particular needs. We carefully maintain confidentiality.

Category // Teklad diet bedding and enrichment