We generally request that clients send us fresh or frozen samples. Freezing is the easiest and most secure way to preserve the DNA. Sometimes, researchers have samples that were already dried. Although not ideal, we can still sequence DNA out of these samples.
For example, we were just asked to compare the diets of two breeds of cattle in New Mexico. Some of the samples had already been dried. Turns out we could get DNA out of them just fine. We’ve had a few other cases where this has happened. Although our success rate isn’t a 100% with the dried samples, it’s still pretty high. We haven’t run the tests to sample fresh and dried subsamples of the same sample, but if the samples are already dried, all is not lost.