Frozen mice with slit throats

[ineedsoap16]

Hey all, been a while since i've been active here. We had our first daughter in November so that has been pretty much full time. I usually buy bulk frozen rats and mice online and recently I've run out and had to go to the local pet shop to get snake food. This shop always has frozen in pretty much whatever I need and it always has seemed to be good quality, the only down side being the marked up price. The other day I went and got a coupla rats and mice and when I went to thaw them I noticed that the adult mice had their throats slit. None of the rats just the adult mice. I haven't had a chance to go back and ask the owner why.

They semed like regular frozen mice, clean and dry. I can't imagine some kind of lab testing deal because I cleaned them up and looked under magnification and the basic anatomy was all still there intact.

Anyone got any ideas or seen this before?