Mouse reproduction - basics
Scientific name: Mus musculus
Weight: 20-80 g (depending on the line)
Lifespan: 1-2 years
Sexual maturity: 4-7 weeks
Breeding maturity: 3-4 months
The sexual cycle: estrus occurs throughout the year, every 4-5 days
Pregnancy period: ~19-21 days
Litter size: 4-14 (and more), average 12
FEMALE
Origin:
First, is the female a purebred mouse obtained from a verified breeder and the breeder has been informed of the intention to breed? Is her genotype and ancestors known?
Age:
Sexual maturity does not equate to breeding maturity. Reproduction of the female too early can lead to complications during childbirth as well as her death.
The optimal age of the first litter is 3-6 months. A female should not be bred more than 3 times, usually 1 time is enough.
There should be at least 2 weeks between litters, and optimally more than a month of break. She is entitled to the breeding pension at the maximum age of 1 year.
Health:
The female must be in great condition, any concerns about her health exclude breeding. You should also remember about diseases invisible at first glance, which the mother can pass on with her genes to her offspring. Mental/neurological health also needs to be considered. The mouse jumps maniacally on the ceiling of the cage? Does he bite the cage? Has balance problems? Does she bite her friends' fur (Berbering)? Does it seem so "untouched"? Don't breed her.
Purpose:
When we plan to breed a pair of animals, we must have a reason for it.
Does the mother have any unique characteristics that we want to pass on to our offspring? What are these features? Will it help us achieve our breeding goal? Thinking about it in advance will make it easier for us to choose the right male.
MALE
Same as above, plus:
Age:
The male may be intended for reproduction a little earlier than the female, but it is worth waiting until about 4 months of age to rule out the occurrence of late congenital diseases.
There is no upper limit.
Attitude to other mice:
We do not use aggressive and too territorial males for breeding.
Purpose:
A pair of animals should be matched and not accidental.
This is a slightly more complicated topic and will be covered elsewhere.
A very interesting article on rodent selection and breeding methods:
---> https://www.afrma.org/breeding-inoutline.htm
Merge organization
The breeding mice live together in one cage. Estrus occurs every 4-5 days. Usually, about 13 days after mating, the first signs of pregnancy appear in the female.
As soon as we notice a rounded belly, the male should be separated into a separate cage.
Leaving the male with the female is a risk of another pregnancy in postpartum estrus.
The developing pregnancy during the rearing of the previous young is a huge burden for the mother's body, and as a result, the puppies from both litters are weaker.
Young development
Baby mice are born bald, blind, deaf and completely dependent on their mother. Through the thin skin, we can assess the state of feeding of the young (thanks to the milky clearness in the stomach area).
After a few days, the first pigment begins to appear, and after a week, micro-hairs break through the skin, creating a characteristic "dandruff" on its surface. This is the time to start socialization (8-10 days). At the beginning, literally a few minutes a day, with time, "stealing young" can be slightly longer.
At the age of 13-14 days, the babies begin to open their eyes and slowly take their first steps outside the nest. Mom still tries to bring them back, but over time she realizes that there is no point in doing so. :P
From about 15 days to even 3.5 weeks they enter the so-called. "jumper period". They are very vigilant, and when frightened, they jump everywhere. No wonder, after all, it is their fight for life against a potential predator. At this time, it is worth avoiding lifting the young outside the cage area and without protection (holding the tail, like "on a leash"). When panicked, they may injure themselves or jump out of their hands and run away.
dandruff
despite bald skin, the pigment is already clearly visible
a well-fed baby
They slowly start to try solid food, and at the age of about 21 days they stop feeding with mother's milk completely. However, it is not yet time to separate the little ones. The recommended period for males to be separated from their mother is 25-28 days.
The females stay with their mother for a few more weeks, the males with each other.
They can go to new homes no sooner than 5-7 weeks.
This is also the time to choose the best puppies from the litter for further breeding. :)
If the decision is difficult - take your time.
It's always better to wait longer than regret your decision later.
Text: Karolina Patalan, Mysigonek kennel