Back to Basics: Mouse Husbandry. Tamara Godbey Clinical Veterinarian University of British Columbia

Transcription

1 Back to Basics: Mouse Husbandry Tamara Godbey Clinical Veterinarian University of British Columbia

2 Overview Mouse specific behaviors Which are necessities? Best practices-not industry standard How do we apply this to today s issues: Genetically engineered mice Ventilated cages (study-mouse Preference for Cage Changing Interval) One size does not fit all

3 Activity Lab mice spend <50% of time active Food provided (foraging?) Mate provided (not always what they were looking for!) Small home range (Meters to kilometers?) Activities follow circadian rhythm Grooming accounts for up to 17% of active time in lab animals Self-grooming-hygiene and insulation Allo-grooming-social and info about food Food consumption mostly at night

4 Specific behaviors Nest building Will readily build nests with a variety of substrates Breeding femaleprotection of pups Non-breeding micethermoregulation, avoidance of light (retinal degeneration in albinos), avoidance of threatening stimuli, avoidance of high air flows in ventilated cages Tunnel building Chewing/Gnawing

5 Nesting-Isn t it a necessity? 39 mice given nesting material-36 built nests within first dark cycle, 3 built nests in 48 hours (Sherwin, 1997) Individual mice spend more time in nest (Watson, 1993) Mice will work to gain access to nesting material Nesting doesn t appear to affect behavioral tests Nesting decreases male aggression Nesting may overcome aversion to high ventilation (Baumans et al, 2002) Nesting improves breeding success

6 Nesting-Have we thought this through? Tissues or paper towel most preferred, paper preferred over wood (Van de Weerd, 1997) Nesting with two different materials (Sherwin, 1997) Mice prefer bedding with larger pieces (Blom et al, 1993)

7 Nesting-Special Strains Debilitated/sickly mice will not benefit from some types of nesting Decrease nesting ability Transgenic/KO strains LPS treated mice, bacteria challenged mice Nesting in these mice is crucial for thermoregulation Need to consider prepared nest material Shredded paper towel, tissue, crinkly paper, etc

8

9 Cage Changing Cage changing considered a stressor-mice with daily cage change failed to gain weight, inc. heart rate and body temp., etc. Bedding in animal cages or pens should be changed as often as necessary to keep the animal clean, dry and relatively odor-free and ammonia levels in the cage at appropriate levels. In rats, this is 25ppm (CCAC, Guide Vol 1 (2 nd ed).

10 Cage Changing Ventilated cages-industry Standard Change from weekly or twice weekly cage change to once every days

11 Cage Changing Mice exhibit preferences for the location in which they defecate (Sherwin (1996), Blom et al (1993))

12 Cage Changing Interval? Animal Welfare Enhancement Award, Johns Hopkins Center for Alternatives to Animal Testing and Animal Welfare Institute

13 Number of Groups Figure 2. Nest position by cage for all 21 groups at 96 hours. Nest Position Cage (days soiled) -no difference in males vs. females -younger animals (<150 days) had a higher preference for 0 day -dwelling time and nest position were associated

14 Cage changing Interval Similar study by Blom et al Mice preferred clean cages over soiled cages as resting, grooming and digging were done mostly in clean cages Optimum frequency of cage changing once per 2-4 days depending on age of animals and number per cage Older animals and more densely housed animals avoided the unclean cage Mice prefer cages that are familiar, however, when soiling became too high the familiar cage was avoided

15 Final thoughts.. Still many uncertainties, esp. by strain or TG/KO Need to use natural behavior as a starting point Nesting appears to be a certainty! All mouse environments should have food, water, bedding, nesting Enrichment should be in addition to above Need to evaluate cage changing interval in more detail Likely that day interval is not best for mice