It varies. Wired, huh?
Well, some labs tend to make their Liquid Cialis on the weak side, so your rats won't enjoy the full benefits.
RUI's Liquid Cialis (30mg / ml) is quite good, I tend to dose it at 2ml and it works like a charm. 1ml did nothing for my rats.
I would have your rats try a 30 mg dose first and see how they feel.
Good luck, bro..