Financial data giant Bloomberg has changed the way it gathers information on European bond market — a fresh example of the teething problems experienced by the industry as it digests the EU's vast new trading rulebook.

The European Union's revised Markets in Financial Instruments Directive, which went live on January 3, requires traders to publish live data on the price and size of the most heavily-traded — or liquid — bonds to ensure regulators have a clearer view of the opaque market for these assets.