No, animals and creatures are never penalized for their "skins".
Also, please remember that it was the original designers of RM who determined the DB values for all of the animals and creatures not the current ICE.
As for races in C&T, The AT says what armor they are wearing. For example, the AT (DB) for a Dwarf in C&T is 16 (35s). That would say that the typical Dwarf (non PC) is wearing Chain Armor (AT 16), and that he has a DB of 35 which includes the use of a shield (the 's' in the DB section).
The original designers often worked in a small fudge factor as well, so that may also be part of the DB of a given race/animal/creature.
But, on the whole, I would treat the entries in C&T as already having all penalties and bonuses factored in -- unless you decide to give them some magical treasure, in which case you ought to just add those bonuses/abilities to the whole.