In addition to the querying feature, the Metadata Service produces two aggregates for bulk download. They can be used in place of the legacy InCommon aggregates should you not be able to take advantage of the MDQ protocol. The IdP-only aggregate, in particular, is useful for discovery services to retrieve/list IdPs in the federations in the discovery UI.
Configure your client with an aggregate below just like you would any hosted metadata, or how you had previously configured your client to use the legacy InCommon aggregates.
You will need to configure your clients to use new signing keys issued for the environment you wish to download metadata from. The aggregates available are: