If you are maintaining the same breeding cage and transferring animals in, mLIMS will not recognize the newly transferred animals as part of the mating.
The best option is to create a new mating with the same name and cage.
In system settings, go to the matings tab and allow duplicate mating names.
You can now transfer the new animals into the existing breeding cage, and set up a new mating directly from that cage using the same mating name.
Select all of the animals that are included in this mating. Do not select animals that are being replcaed. Name the mating the same as the previous mating.