Question: The lab is about to receive a shipment of mice. How do we house them? It's urgent!

Answer: Don't panic. This article provides a guide to mouse husbandry. After reading, you'll know how to be an excellent "caretaker." Let's start with environmental conditions.

 

01. Environmental Conditions
 

1) Microbial Status

Unlike wild mice that can carry various infectious diseases, laboratory mice are bred and maintained in specialized environments. The most widely used standard internationally is Specific Pathogen Free (SPF).

2) Temperature and Humidity

● Temperature: The optimal temperature range for mice is 20-26°C. Fluctuations should be controlled within ±2°C. The temperature inside a mouse cage is typically 1-2°C higher than the room temperature.

● Humidity: Relative humidity should be maintained at 40%-70%, with the optimal range being 50%-60%. Excessively high humidity promotes bacterial and fungal growth, while overly low humidity can dry out the mice's respiratory mucosa.

3) Air Quality

● Ammonia Concentration: Ammonia is a primary contaminant from the decomposition of mouse feces and urine. Its concentration should be kept below 20 ppm. High ammonia levels can irritate the mice's respiratory tract and eyes, causing inflammation.

● Ventilation: The animal room's air exchange rate should be 10-20 times per hour, with an air velocity of less than 0.2 m/s, ensuring fresh air.

4) Lighting and Noise

● Lighting: Mice thrive in low-light conditions. Light intensity in the housing room should be controlled at 15-20 lux, with a 12-hour light/dark cycle (e.g., 12h/12h or 10h/14h).

● Noise: Noise in the housing room should be kept below 60 decibels to avoid stress responses in mice from loud sounds.

 

Question: How do we choose cages, bedding, and other supplies?
 

02. Caging and Housing Facilities

1) Cage Selection

● Material: Transparent or opaque plastic cages made of non-toxic material are recommended, fitted with stainless-steel wire bar lids. Water bottles can be made of glass or plastic with stoppers equipped with metal or glass sipper tubes for automatic watering.

● Size: Choose cage floor area based on mouse weight and number housed. For example, a single mouse (<20g) requires a minimum floor area of 0.0067 m²; for group housing, the minimum is 0.042 m².

● Structure: Cages should have smooth, rounded corners without sharp edges to prevent injury. Laminar flow cabinets and Individual Ventilated Cages (IVC) are commonly used equipment, maintaining clean air via HEPA filters.

2) Bedding and Enrichment

● Material: Bedding should be highly absorbent, low-dust, odorless, and non-toxic. Examples include wood shavings, corncob, or recycled paper.

● Processing: Bedding must be sterilized via autoclaving or ⁶⁰Co irradiation to eliminate potential pathogens. Change bedding regularly, typically twice a week.

● Toys and Enrichment: Provide enrichment items like red transparent shelters (igloos) and nesting material (e.g., paper strips) to satisfy mice's natural behaviors for shredding and nest-building.
 

 

3) Feed and Water

● Feed: Mouse diet must be nutritionally balanced and protein-rich. Choose feed formulations appropriate for different life stages: growth, breeding, or maintenance. Feed should be regularly sterilized to prevent pathogen spread. The two main sterilization methods are pre-vacuum autoclaving (reliable but may degrade some nutrients) and ⁶⁰Co irradiation (minimal nutrient loss but higher cost).

● Water: Drinking water must be clean and contaminant-free. It can be treated via filtration, acidification (pH 2.5-3.0), or autoclaving. Water bottles should be changed and refilled with fresh water twice a week.

 

Question: Mouse waste like feces, bedding, and carcasses need to be disposed of. How should that be handled?
 

03. Waste Management

1) Segregated Collection

Separate waste into biological waste (e.g., feces, soiled bedding, carcasses) and non-biological waste (e.g., disposable items, cleaning tools). Biological waste must be collected separately to avoid cross-contamination.

2) Disposal Methods

● Biological Waste: Feces and soiled bedding can be disposed of by high-temperature incineration or composting. Animal carcasses must be frozen and then sent to professional facilities for appropriate disposal (e.g., incineration, rendering).

● Non-biological Waste: Disposable items should be disinfected and treated as medical waste. Reusable tools require thorough cleaning and disinfection.

3) Records and Oversight

Maintain waste disposal logs detailing the type, quantity, disposal method, and date. This facilitates traceability and regulatory compliance.

 

References:

[1] Wang Tao. (Year). Housing Management and Growth Observation of Mice. In Proceedings of the 10th National Nutrition Academic Conference and 7th Member Congress of the Chinese Nutrition Society.

[2] Xu Jianteng. (2005). Key Points for Housing and Management of Common Laboratory Mice. Jiangxi Feed, (1), 1.

[3] Relevant information from laboratory animal resources.

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