Open tub throw rat close tub and repeat
Open tub throw rat close tub
Open tub throw rat close tub
Open tub throw rat close tub
....

Once everybody is fed start back from the beginning and

Open tub, make sure rat is gone, remove rat if un-eaten and repeat...

All the un-eaten rats (not many) usually go as a second serving to the voracious eaters so I don't have to take them back to the rat room.