where can I send a dead rat for an autopsy?

So after a round of antibiotics in the water and changing the food to get rid of the corn I still had a few rats just drop over dead this week. No signs of stress the day before, no signs of fighting, only a few medium rats in a 40 gallon, not over crowded. Had one die in my male tank and one in my female tank, bummer because I was growing these up to breed. The last one was still warm when I saw him, looked like he died in the last few minutes, so I popped him in the freezer in a baggie. Maybe I can get someone to help me solve this? It may be diet related, I'm actually getting an ARS rat breeder rack and Mazuri lab blocks this week or next, should eliminate the diet related question...

Your vet would know. Are you near a university that has a veterinary program? That option might be less expensive.

Any Vet can do a necropsy however the animal should not be frozen just kept cold in the fridge. As far as elimanating corn it won't be easy, corn is also the first ingredient in mazuri rodent food.

I would be surprised if it diet related unless you feed a diet too reach in protein, leading to kidney failure.