I do use the state lab to identify any health issues going on in my flock and with my livestock. This helps to know exactly what the problems are and also, what diseases aren't present in my flock. Otherwise, you are simply guessing. This goes hand in hand with the culling for symptoms, not as an alternative. At least here in CA, they won't quarantine your entire flock unless it's something very serious ie Newcastle. In that case, depopulation would be warranted.