ICR i assume is labe mice. i do both et store and labe mice. i have also noticed that the lab mice do not do as well with the regular mice. their immune system is not as good. but then they produce 2 times more babies. regular mice i get 8 to 10 babies as the lab mice give me 20 to 25 babies. they are wirth it as this is my buisness but their breeding expectancy is only 4 months in my experience. they simpley do not do as well out side of sterile enclosures. kinda like the boy in the bubble really.