24-bit 192 KHz support for Airplay and Airport Express?

How to get iTunes to stream my 24-bit and 192 KHz ALAC songs to Airport Express over WiFi? When I do, the music is somewhere converted down to regular CD format och 16-bit 44.1 KHz. If I instead connect using USB direct from my Mac or PC to my DAC it sends out 24-bit 192 KHz, so is this a restriction in iTunes network streaming or in the Airport Express, and how do I hack it?

Has Apple told anyone when they will support 24-bit and 96/192 KHz HiFi resolution music as the other devices like Logitech and Sonos that does this already?