JAX Notes July 01, 2008

A guide to unpacking and working with C57BL/6J diet-induced obesity (DIO) mice

JAX® Mice and Services provide both "DIO-on-Demand" inventory and custom DIO mice. For "DIO-on-Demand" inventory mice, C57BL/6J males are started on 60 kcal% fat diet (Research Diets, D12492i) at six weeks of age and are maintained on that diet for up to 26 weeks of age. Control mice, fed 10 kcal% fat diets (Research Diets, D12450Bi) from six up to 26 weeks of age, are also available from our inventory. DIO-on-Demand mice are available from our Bar Harbor facility.

The following information contains a few observations on the condition of DIO-on-Demand mice and suggestions for handling and using them:

Appearance

Mice fed 60 kcal% diet may appear “greasy” or “wet” on arrival. This is normal. We have observed that mice fed high fat diets have greasy or wet coats from rubbing against the diet in their cages or shipping boxes and, potentially, from metabolizing the extra fat in their diets. Control mice, fed 10 kcal% diet, have a normal coat appearance.

Shipping stress and acclimation

All mice can experience some stress and concomitant weight loss during shipment. Although DIO-on-Demand mice are shipped with a gel-based water source and appropriate food, they may lose weight during transit. Therefore, we recommend that you acclimate these mice in your vivarium for a week to 10 days before using them. During that time, they should be fed the appropriate diet (60 or 10 kcal% diet) and have access to water ad libitum. In our experience, acclimation ensures both that the mice regain any lost weight and that their physiological parameters adjust to their new environment.

Assigning mice to study cohorts

Throughout the diet preconditioning, DIO-on-Demand mice are housed in 10-mouse cohorts, which are maintained during shipping. We strongly encourage you to maintain the integrity of these cohorts; that is, do not co-house mice from different shipping containers or from different compartments within a single shipping container. In our experience, mixing established groups of male mice can result in fighting or other dominance behaviors that can negatively impact weight gain and general condition. We recommend that the 10-mouse cohorts are maintained or that each cohort is divided into smaller groups, such as five males per cage, for housing and studies.

Managing the mice

To keep stresses of DIO mice to a minimum, we recommend the following:

  • Position cage racks a couple of inches away from any wall that transmits disturbing vibrations (e.g., from equipment such as air exchangers).
  • Place cages away from any door or sink where there may be heavy traffic or loud noises.
  • Remind caretakers to work gently, slowly and quietly when handling the mice.
  • Change cage bedding only once a week.
  • Resist the temptation to check on the mice too frequently.
  • Handle the mice with gloves (a fresh pair for each cage) or forceps.
  • Try using nestlets or kimwipes for nesting material.