I would direct you to 10-208 for 2 or more buildings fed from a single service, and the rule talks specifically about buildings housing livestock. Essentially separate grounding electrode at each building, each panel neutral bonded to this electrode.
And you need the bond wire for the receptacles otherwise the 6/32 screws used to mount the recetacle become the bonding method which is not approved as per 10-804. Maybe refer also to 26-714 if the outdoor receptacles are part of a single family dwelling on the farm, ie GFCI protection.
