Feeding Mice

Common house mouse (Mus musculus)

They are readily available in international databases

By mating unrelated animals in a closed colony

Incisors

Malocclusion

Firm and rice-sized

To promote a faster recovery

19-21 days

10-14 days

4-12

Constant light exposure

A population of animals that are genetically variable and bred to maintain maximum heterozygosity.

Swiss Webster

Inbred strains have genetically identical individuals, while outbred stocks have genetically variable individuals.

To produce animals with nearly the same genetic composition.

Shining a red-filtered flashlight

Flattened, lateral ears

Carbon dioxide (CO2) asphyxiation

Solid-bottom plastic cages

All of the above

4 to 5 mice

Sterilized feed

Using plastic restraint devices

Tunnel handling

Holding the head firmly but gently

Toe clipping

Social dominance hierarchies

To prevent aggression

A harmless behavior of overgrooming by dominant mice

Pick them up by the base or middle of the tail

An outbred stock is a closed population of genetically variable animals that maintain maximum heterozygosity, while an inbred strain is developed by breeding related individuals for many generations to achieve nearly the same genetic composition.

Swiss Webster, CD-1, ICR, CFW

Hybrids are designated by combining some of the designations of their parents. For example, breeding a female C57BL/6 with a male C3H produces B6C3F1 offspring.

Transgenic mice, knockout mice, and nude mice

Mice are commonly used in biomedical research due to their status as the most commonly worked with animal species in this field. They provide a valuable model for studying human health and disease, as international databases provide integrated genetic, genomic, and biological data for the mouse. Mice are efficient breeders, producing many generations in a short time period. Additionally, the availability of genetically modified mice allows for research in various areas, including genetics, cancer, and infectious diseases.

The most widely used species of mouse in research is the common house mouse, Mus musculus. While other species such as field (Microtus spp.) and deer (Peromyscus spp.) mice are occasionally used in the laboratory, the information presented in this chapter refers specifically to Mus musculus.

Outbred stocks are created by mating unrelated animals in a closed colony. This produces a population with a 'stabilized' genetic composition.

Gender, strain, territory, fear-induced defensiveness, and social dominance are some factors that can contribute to aggression in mice.

Barbering is when a behaviorally dominant mouse overgrooms the fur of more subordinate cagemates. To decrease this behavior, mice should be offered various forms of environmental enrichment.

Mice should be picked up by the base or middle of the tail, and not by the tip of the tail to avoid causing the skin to tear off the tail, known as 'degloving'.

Some methods of restraint for handling mice include tail restraint, grasping the scruff of the neck while securing the tail, and using rubber-tipped forceps to grasp the scruff of the neck.

Malocclusion in mice is a condition where the incisors are not properly aligned, causing them to become overly long. This can lead to damage or piercing of the gums and difficulty in eating. Treatment involves clipping the overgrown teeth to the proper length, although periodic clipping will be needed for the life of the animal.

The dental formula of mice is 1 0 0 3 / I C P M / 1 0 0 3.

Mouse feces are firm, rice-sized, and dark brown in color. Mouse urine is clear, yellow, and has a strong odor.

Mice do not vomit because they lack the neural pathways for vomiting and the connection of the esophagus at the stomach prevents regurgitation. This means that feed and water are normally not withheld prior to anesthesia. However, withholding feed and water can make mice prone to dehydration and hypoglycemia, so it is important to prevent these conditions for the mouse's recovery from surgery.

To check the activity level of mice

To assess pain in mice

Carbon dioxide (CO2) asphyxiation and an overdose of anesthetic gas (such as isoflurane)

The milk spot in newborn mice is a distinct white spot visible through the transparent skin on the left side of their abdomen. It indicates that the mice are healthy and nursing normally and that the mother is producing milk.

Mice reach puberty at around 5-7 weeks for males and 4-5 weeks for females. The gestation period is 19-21 days and the litter size is typically 4-12. Mice are non-seasonal polyestrus, meaning they can mate throughout the year. Weaning usually occurs between 21-28 days.

Mice are nocturnal animals, with most of their activities taking place when it is dark. They have alternating periods of activity and rest during both day and night. When sleeping, a mouse may curl its head under its body.

Environmental factors such as constant exposure to light, loud noises, and vibrations can decrease reproductive performance in a mouse colony. Inbred mouse strains and genetically modified strains may also exhibit lower reproductive performance.

The different methods of handling mice include picking up by hands, tunnel handling, cup handling, and plastic restraint devices. Picking up by hands and tunnel handling are best used for transferring animals between cages, while plastic restraint devices are used for research procedures. Cup handling is a technique that involves keeping the animal in a cupped hand without restraint.

The different methods of individual identification for mice include cage cards, ear notching, ear tags, tail or toe tattoos, microchips, nontoxic color markers, and toe clipping. The use of toe clipping as a method of identification requires IACUC approval and should only be used when no other method is feasible.

Mice should be fed and watered ad libitum, meaning that feed and water should always be available. Standardized, nutritionally complete rodent diets are readily available from multiple vendors.

Outbred stocks of mice are genetically diverse populations that are used for their genetic variability. Inbred strains of mice are created by breeding related individuals for many generations to produce genetically identical individuals. Outbred stocks are commonly used for general research purposes, while inbred strains are used for specific research applications that require genetic uniformity.

Solid-bottom plastic cages with bedding are commonly used in most facilities. They prevent exposure to airborne pathogens and can be used with microisolation lids to reduce moisture buildup. Ventilated caging systems provide air circulation and reduce the frequency of cage changes.

Enrichment allows mice to exhibit species-typical behaviors, make choices in their environment, and decrease stress.

Examples of enrichment options include nesting material, hiding places, foraging material, and nutritional enrichment.

Sick or injured mice often display similar signs regardless of the cause.

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