Dual configuration bottle assembly

A bottle assembly comprising:

• a container having an open end, a closed end, a base portion, and a neck, the neck having a rim defining the open end of the container;
• a vent assembly positionable on the rim of the container to enable venting of the container during use;
• and
• a collar assembly generally defining a closure for the container, the collar assembly configured for releasable engagement with the neck of the container over the open end thereof,
• wherein the collar assembly and the container are configured relative to each other to enable selective configuration of the bottle assembly between a first configuration and a second configuration,
• wherein in the first configuration, the collar assembly is configured to sealingly engage the vent assembly and urge the vent assembly into sealing engagement with the rim of the container, and
• wherein in the second configuration, in which the vent assembly is omitted from the bottle assembly, the collar assembly is configured to sealingly engage the rim of the container.