Are you talking
Defensive Fighting or
Epic Defensive Fighting? Because there's no good reason to use the former. If you're playing a DPS bear, you're running Power Attack + Rage of the Beast, both of which are incompatible with Defensive Fighting. Oh yeah, and casting a spell disables Defensive Fighting too, so...kind of a no-go for any caster.
S&B bears keep the static bonuses from their shields, but you can't shield-bash in animal form so bonuses like Improved Shield Bashing have no effect. Also the Shield Mastery feats have no effect. Not sure about Shield Deflection.