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.
If you have decided to breed your rats, you must also consider their age. The best time to breed a female for the first time is at 4-5 months of age. It can be dangerous to breed a female older than 6-8 months of age for the first time, since her pelvic canal will be fused in a narrow position.ats can reach sexual maturity at 5 weeks of age, so the sexes should be separated prior to this age. Rats do not recognize incest, so brothers and sisters and even mothers and sons must be separated. Rats do not have a breeding season, although very hot or cold temperatures will reduce breeding.