Mouse pregnancy how long

House the females in large groups with no males nearby. By doing this, diestrus is prolonged and estrus is suppressed, a phenomenon known as the Whitten effect. Because pheromones from male mice can interfere with this effect, olfactory stimulation of the group-housed females by male mice must be prevented.

When the females are placed with males typically females per male , the estrous cycle of most females will restart within three days. To identify those that have mated, examine them daily for a vaginal plug. The presence of a vaginal plug does not guarantee pregnancy: it only indicates that sexual activity occurred.

The likelihood of pregnancy after mating varies with the mouse strain and with the phase of the estrous cycle when mating occurs. For most strains, the rate of pregnancy is highest among estrus-suppressed females with vaginal plugs found the third day after being placed with a male.

If the plugged female is pregnant, the first day of gestation is considered to be the day after the plug is found.

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Please refer to our privacy policy for more information. What is Personalized Medicine? Genetics vs. Evaluating vaginal cytology To obtain a vaginal specimen for determining the stage of the estrous cycle, insert a moistened cotton-tipped swab into the vaginal opening of a manually restrained mouse.

Just one female mouse in your home can average between 25 and 60 offspring in a single year. At that point, you no longer have a mouse problem — you have a mouse infestation.

When a female mouse gets pregnant, it only takes between 19 and 21 days for her to give birth to a litter. A typical female mouse can birth between five and 10 litters per year. She can mate immediately after giving birth, meaning mice can birth a second litter in as little as 25 days after the first. This cycle continues until the mouse dies.

The pups are born without fur, ears or the ability to see. These early days in the life cycle of a mouse are filled with rapid progress. On the fourth day, their ears are fully developed.

Hair begins to grow around the sixth day, and by day 10, they have a protective coat of fur. If you need to expand a strain quickly, you can mate females in estrus with the males every day and check plugs the next morning.

House females of similar plug dates together through to weaning of the pups. For many strains, two pregnant females and their litters can be housed together until weaning, although you may find that particularly fecund strains like CD1 require that the cage be split to avoid overcrowding. The IACUC guidelines for mice with litters limit the number of mice to 2 adults and no more than 20 pups.

How long is gestation? Gestation is 18 to 20 days, depending on the strain. How can I prevent mothers from cannibalizing their litters? Mice are social and care better for their young when they are housed with friends. House females continuously with the sire, or house pregnant females together, or house a pregnant female with a non-pregnant female.

However, do not add mice to a cage just a few days before birth, as this will disturb them. First time mothers and very young females are less likely to raise a litter successfully than experienced mothers and more mature females. Mothers and their litters should not be disturbed the first day after birth. By the second day, mothers should have acquired full maternal behavior and will tolerate disruptions better.

Adverse environmental conditions such as sudden loud noises and inadequate ventilation can also have a detrimental effect. Some strains are more maternal than others see Jax' listing of strain characteristics. In difficult situations, you can foster the pups to a more maternal strain or cohouse a pregnant mouse of a maternal strain at the same or more advanced stage of pregnancy with a different coat color together with your problematic mom.

You can keep one or several cages of outbred mating pairs for example, CD1 mice from Charles River on hand for fostering pups. A detailed description of how to foster mice provided by the Jackson Laboratory is available here.

In addition, see the section below on increasing reproductive performance. When should mice be weaned? Mice should be weaned at 3 to 4 weeks after birth. Pups must be weaned if the same mom gives birth to a second litter. The pups should be robust, active, have open eyes, teeth and adult fur rather than the sparser fur of babies.

They need to be able to jump up to the top of the cage to feed and drink. If they are too immature, let them go longer with their mom. In many strains, pups ready to wean will "popcorn" when the cage lid is opened. If you are uncertain about their ability to well on their own, you can leave a little water-softened food in the bottom of the cage to help them through the first day or two.

When do mice become sexually mature? Female mice become sexually mature at 6 weeks after birth and males at 8 weeks. What are the acceptable methods of euthanasia? Mice are narcotized by CO 2 inhalation and then euthanized by cervical dislocation.

Although CO 2 alone can euthanize the animals, it must be ascertained if the animals have died see the NIH guidelines on the use of CO 2 alone , thus cervical dislocation is recommended after the use of CO 2. CO 2 must be delivered from a tank , not from dry ice. The ARC provides tanks and chambers. Let the gas flow for 1 minute to fill the chamber and leave the chamber closed for 5 minutes.

The narcotization of mice is rapid, so do not leave the chamber unattended. Death should be ensured by cervical dislocation. The mice must not be overcrowded, and must have sufficient food and water to last through working hours of the next working day.

If unweaned pups are left without their mother, the ARC must be notified immediately so that euthanasia may be performed without delay. CO 2 for euthanasia is cheap, convenient, effective and poses little risk for staff and investigators, but the humaneness of its use is increasingly debated.

An alternative method of euthanasia is to anesthetize the mice with isoflurane before cervical dislocation. In a chemical fume hood i. When the mouse is immobile, open the chamber and perform cervical dislocation. Be aware that isoflurane is a health hazard, and exposure to personnel should be avoided by confining use to chemical fume hoods and anesthesia apparatus and by proper storage. Mice may be euthanized by cervical dislocation without anesthesia by experienced, competent individuals, if scientifically justified.

Cervical dislocation is performed by picking up the mouse by the base of the tail. The mouse is allowed to grip the bars of a transversely oriented cage top and while pulling gently backwards by the tail, the base of the skull is firmly gripped between thumb and index finger.

To ensure humane euthanasia, cervical dislocation should be learned under supervision of a qualified individual.

What are the acceptable methods of euthanasia for fetal and newborn mice? Newborn mice can be narcotized in a small plastic bag with CO 2 from a gas cylinder, the bag is sealed, then the mice are euthanized by placing in a freezer. Complete CWRU IACUC regulations and recommendations on acceptable methods of euthanasia of fetal mice over 14 days of gestation , newborn mice and young mice are available here.

What are the acceptable effective ways to mark mice? The external ears are large enough to ear punch after 2 weeks of age. However, ear punches can become difficult to read after several weeks because of healing. For more permanent marking, removing the last joint of a toe without anesthesia during the first week after birth is acceptable. Only one toe can be clipped per limb.

Anesthesia must be used for toe-clipping of mice older than one week. A scientific justification must be provided for the use of toe-clipping instead of other methods of identification. Tattooing is an acceptable alternative, although it is less commonly used. India ink in a 1 ml syringe with a 30 gauge needle can be used to mark paws in different combinations. In some instances, genotypes are needed at birth: tattooing with India ink of newborn paws with tail clipping works well in practice.

Implanted ID transponder chips are an alternative, if cost and labor are no obstacle. How are mice genotyped? An efficient way to manage your mice is to wean, ear punch, and genotype at the same time. Genotyping by PCR is the most efficient. Ideally, the PCR primers are specific to the mutation, rather than a generic set like primers to neo R or lacZ. Extensive information on developing and validating assays for genotyping mice is available here.

A simple and reliable protocol for PCR from ear punches is provided here. Alternatively, Southern blots can be performed on toe DNA prepared by the method outlined here. How are males and females housed? Don't the males fight? Females can be housed five to a cage, and can be mixed with unfamiliar females without problems. Special attention must be paid to the housing of males because of their propensity for fighting.

Males will generally not fight if they are housed together from before sexual maturity through to old age. After sexual maturity, males will fight when introduced to a new male. For example, males that have been housed alone will fight with any introduced male. Therefore, stock males from the same litter should be housed together from a young age to conserve space.