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. Reproductive time frames will vary between different rats and/or lines of rats. Environment, health, lineage, and nutrition are a few of the factors that can affect reproductive life. Although it is not advisable, some female rats can be capable of breeding at 6 weeks.In rare circumstances breeding has occurred as early as 5 weeks. This is why it is best to separate the sexes when a litter reaches 5 weeks of age.s they age their reproductive organs will become less suited for pregnancy and birth and the eggs will become less viable. Male rats can impregnate a female as young as 5 weeks, although that is not common. They are able to breed for most of their lives.