Mouse Husbandry and Care

Last Review Date: December 30, 2020

I.       Purpose

This Standard Operating Procedure (SOP) outlines the animal care requirements associated with the daily husbandry of Specific Pathogen Free (SPF) mice to ensure consistent and uniform care. This procedure applies to all LAR staff members and researchers involved in the care of SPF mice housed in static micro-isolator and in individual ventilated caging (IVC) systems on the main campus of the University of Montana.

II.      Policy

It is a LAR policy to meet or exceed all federal, state, and local regulations and guidelines and to comply with all institutional policies and procedures as they apply to the use of animals in research. LAR animal care staff and animal researchers must pass on-line animal training modules and attend applicable training in animal care and use, occupational health and safety, and equipment operation prior to performing activities outlined in this SOP. Animal housing rooms must be entered using appropriate personal protective gear for the species and disease or hazard containment level.

III.     Morning Observations (7 days a week)

  1. Wear appropriate PPE when entering SPF mouse housing areas. This includes nitrile gloves, lab coats, and masks and hair nets (if applicable).
  2. Record room temperature and humidity. Notify the facility manager if the temperature is in excess of 73oF. 
    • Ideal temperature range 69o to 72o F.
    • Check for any special feeding or watering instructions or specific instructions or requests (i.e. separating harems, fostering pups, teeth, and nail trims) from the Principal Investigator (PI). 
  3. Light timers are set for 12L/12D or as otherwise instructed by PI. 

IV.    Daily Routine and Veterinary Care Procedures

  1. Observe animals for signs of disease, illness, or injury.
  2. Use a transfer station when opening mouse boxes. Open one mouse box at a time.
  3. If mice show signs of wasting, illness, or injury, check all caging materials for defects, including water bottles, lixits, wire hoppers, and cage lids.
  4. Check for wet boxes. If a box is wet, remove mice from the wet box and replace it with a new set up.
  5. Flag boxes where mice show signs of wasting, illness, injury, or disease with a yellow “Vet Check” card and notify the AV, PI, and Facility Manager. For common illnesses and treatments, follow those specific SOPs.
  6. If a mouse is found dead in a cage, follow the instructions below:
    • Record the date and animal ID or cage number on the daily log sheet and change the animal number on the cage card to reflect the new number of mice remaining
    • Remove carcass from cage and place in a clear plastic bag (located by CO2 chambers); mark the bag with the date, PI, ID # and appropriate designation: Tg= transgenic mice, WT= wild type mice, WTD= wild type with drug
      • Place mouse in an appropriately marked area of freezer unless carcass is to be necropsied or saved for tissue. One basket or area is for transgenic mice (Tg) and mice treated with a drug (WTD); only wild type mice will be placed in the raptor refrigerator located in Health Science 015A (key in HS009 office)
      • Carcasses for necropsy should be marked as above but placed in the refrigerator in Skaggs 033 or designated refrigerator in HSB 018A. Do not freeze mice intended for necropsy, as this will ruin the tissue. Carcasses will be kept for one week before disposing.
  7. If a wet box is found:
    • Remove rodents from the wet box and dry off with KimWipe or other absorbable material
    • Replace wet housing box and related items (filter top, hopper, clean water bottle, lixit, and cage card holder) with clean housing set up
    • Shred a new nestlet and place it into a corner with a new TP roll or Twist
    • Leave a sticky note on the box for further checking
  8. Count mouse boxes daily and add that figure to the daily census sheets on room clipboards. If a PI requests per diems recorded for individual AUP’s, place those figures on separate (designated) sheets. 
  9. Record all births and deaths on the daily log sheet together with any vet check notes. 

V.      Harem Breeding and Births

  1. Identify breeding mice with specific Breeder cage cards. These mice include breeding pairs or harems of 3 or 4 mice per cage.
  2. LAR technicians are required to check for births daily. 
  3. Flag breeding mouse cages with Post-It notes if a female mouse is pregnant. The LAR technician identifying and applying Post-It should check these cages carefully for impending births.
  4. Write the date of birth on the breeder cage card. 
    • Attempt to identify the number of pups without disturbing the nest.  If not possible, note the number of pups at a later observation. If a number of pups is determined, write that number on the breeder cage card
  5. Write the wean date on a Post-It note and attach it securely to the breeder cage card.
    • LAR weaning policy (SOP) states pups should be weaned 21 days after birth
    • The day pups are born (found) is day 0, the next day is day 1, so count out 21 days from day 1.  For instance, if pups are born on Jan 1st, their wean date will be Jan 22nd
    • Due to post-partum (after-birth) estrus, female mice can deliver their next litter at the same time the previous litter is due to be weaned. Thus, accuracy in recording births is imperative to prevent pups on pups
  6. A special circumstance in which weaning could be delayed by the PI or AV includes low birth/development weights of certain strains of mice, large litters, or transgenic mice. In such instances, attach a Post-It note with an explanation to the cage card and the date of wean updated.  See LAR Weaning  SOP for more details.
  7. If a new birth is discovered during bedding or complete cage change, or the day before a bedding or cage change, DO NOT change the bedding or cage. Place a “New Litter” cage card (white “New Litter” card”) over the cage card and mark the cage change date for 2 days later (48 hours). (Place that date on the” New Litter” cage card).
  8. The LAR technician scheduled for the daily check will change the cage on the new date and remove the “New Litter” cage card.
  9. When transferring a litter of pups and female (or parents) to a new housing box, collect the pups in your gloved hand gathering as much of the nest as possible including the pups. Gently deposit the pups in nest material in the same area in the new box.
  10. If a litter has 10 or more pups, transfer parents and pups to a condo.
  11. If PI’s are harem breeding (one male to 2-3 females) determine if female mice are exhibiting signs of pregnancy during daily observations.
  12. If requested by a PI, remove females identified as pregnant to their own housing boxes with proper cage identification
  13. If a PI requests fostering of pups and separating pregnant harem females, it is the responsibility of the LAR technician scheduled for the daily room tasks on that day – no exceptions.
  14. Clearly mark all boxes related to any of these changes and notify PI by e-mail and enter on the daily log. 

VI.   Mouse Husbandry – Daily

  1. All mice are fed Teklad 2020x Rodent diet unless the PI is feeding a special diet or requests Harlan 2019 high fat for breeding animals.
  2. Add food to cage hoppers if it appears the amount of food will not last until the next bedding or cage change, or if less than ¼ full. Immediately discard feed that appears wet, moldy, or contaminated with non-food materials.
    • Mouse food is stored in sealed containers in designated feed and bedding areas
    • Containers are sanitized monthly and new feed is added to the containers
    • Mark the mill date, date of fill, and your initials on the container card hanging on the barrel
    • Mouse food expires 6 months from mill date
  3. For newly weaned mouse boxes (up to one-week post-weaning or especially small mice), add a few food pellets to the bottom of cages daily.
  4. Refill water bottles that are less than ¼ full.
  5. Notify PI’s or their designee of deaths or births (if requested) by e-mail or telephone. Clearly state the animal ID number, strain, box number, and date of birth or death. 

VII.  Mouse Husbandry – Weekly

  1. Set up clean materials and fill bedding in mouse boxes prior to cage changing (usually 1-2 days in advance of cleaning day) and stage in areas out of the way of traffic in designated rooms.
  2. Use transfer station to change static micro-isolator boxes weekly, and complete cage washes every 2 weeks.
  3. Refill all water bottles on bedding change days.
  4. Refill feed hoppers, saving the feed in the hoppers if it is not soiled. Do not overfill hoppers and adjust the feed amount by the number of animals in the box.
  5. All mouse boxes must have at least one form of enrichment (autoclaved Nestlet, TP or paper towel roll, Kimwipe, Bio-Serve mouse huts, E. Dri, or Twist).
    • Add hut or TP roll to all boxes exhibiting barbering or with aggressive male mice
  6. Single housed mice require at least 2 forms of the above enrichment.
  7. Add a pinch of dirty bedding from the old box into the new box of bedding with multiple housed mice (this reduces aggression)
  8. Spray racks with Peroxigard and wipe down with paper towels at the time of cage changing.
  9. Change gloves between mouse strains or colonies
  10. Return all cages to their original location on the rack in an orderly manner.
  11. Bedding changes for mice in micro-isolator boxes will be done on alternate weeks from full cage changes (see next section)
  12. Cover all dirty mouse boxes with micro-isolator lids for transport to the dirty cage wash area.
  13. Spray transfer station with Peroxigard and wipe clean after each use.

VIII.    Mouse Husbandry – Every 2 Weeks

  1. All housing materials must be set up prior to complete cage wash in the holding area (as stated above).
  2. A full cage change for SPF mice in static micro-isolator boxes (box bottoms, wire hoppers or feeders, micro-isolator filter tops, cage card holders, water bottles, and lixits) must be done at least once every 2 weeks. On the off week, only the bedding is changed.  Mice housed on IVC (individual ventilated racks) require a complete cage change every 2 weeks (no bedding change on off week unless a wet box is discovered)
  3. Spray mouse racks with 
    Peroxigard at the time of cage changing and wipe down with paper towels to remove dust and debris build-up.
  4. Change gloves between mouse strains or colonies.
  5. Refill the feed in the hoppers and save the feed in the hoppers if it is not soiled (do not overfill hopper and adjust the feed amount by the number of animals in the box)
  6. Return all cages to their original location on the rack in an orderly manner.
  7. Spray the transfer station with Peroxigard after each use. 

IX.       Sanitation

  1. Sweep floors in SPF mouse housing rooms daily Monday through Friday and as needed on weekends.
  2. Mop floors in SPF animal rooms daily Monday through Friday and as needed on weekends with the Peroxigard mop solution prepared daily prior to mopping.  Dispose of old mop solution down the drain.
    • Mix 2 oz Peroxigard Concentrate in 1 gal of water in mop bucket (1:64 dilution)
    • Place dry mop into freshly made Peroxigard solution and thoroughly wet the mop. Squeeze excess water from the mop.  Use this technique to mop the entire room floor making sure not to leave any excess water on the floor
    • Rinse the mop in the bucket and squeeze excess water from the mop. Drape thoroughly squeezed mop over mop press allowing mop to hang over the bucket to dry completely
    • Do not allow the mop to sit inside mop press or in the bucket of Peroxigard
  3. Tidy up all work areas and wipe off sinks, shelves, and racks.
  4. Place small containers of food left in rooms (for weans or topping hoppers in between changes) inside a covered mouse box with mill date and type of feed.
  5. Leave no more than 4 cage set-ups in animal housing rooms.
  6. Empty trash containers daily. Replace the trash bag with a new bag.