5 day old calf with a snotty nose

Sorry about the description! I have a little bull calf that I am bottle feeding while the owner's are away. He eats well, good energy level, and he just started drinking out of a bucket. The drainage from his nose just began this morning and it is an opaque color moving in the direction of green. My question is this: should I treat him with penicillin and how much should I give him and how often? He weighs about 35-40 pounds.

I thank you all in advance.

Melissa