The stomach has three types of contractions: There are rhythmic, 3 per minute, synchronized contractions in the lower part of the stomach, which create waves of food particles and juice which splash against a closed sphincter muscle (the pyloric sphincter) to grind the food into small particles.
7 What is the gestation period, how many babies do they have, and when are they weaned? 1  The gestation period for rats is 19â22 days, for mice it is 17â21 days.  Rats and mice average 8â12 babies in a litter, but can have as few as 1 or as many as 20.
Breeding Age: Female rats can get pregnant very young. Its best never to keep males and females together past the age of 6 weeks. Best breeding age should be based on the size of the female: As long as the female is sufficiently grown, 4 months at the earliest with 6  7 being optimal. Females in good health and body structure can be as bred as late as 10 months and later depending on the genetic line. If you are not familiar with the line you are breeding, it might be best to breed the doe earlier. Male rats are generally good breeders at the age of three months.