Removing or modifying bridges between truss or joists to make way for ducting
Bridging (or blocking) between trusses or joists is used to keep the trusses or joists from “laying over” under heavy loading. Randomly removing a few pieces of bridging is not serious, because adjacent pieces of bridging will still keep the trusses and joists plumb. 

However, in your case, the “bridging” is something else. I doubt it’s bridging because 1) the trusses are fastened to it with steel connectors, 2) the solid member is continuous, not discontinuous between the trusses, 3) the solid member is more than 38 mm (1 1/2”) thick. 

I’m thinking that solid member is a structural beam, not bridging. Do NOT remove it or notch it until a structural engineer (not civil engineer) or an architect can review it.