The HUGE, bulging titties that hang from a female dog when she has not fed her puppies for a week.
When driving around on the dirt roads in the South African East Cape Coast, you see a lot of 'mommy' dogs who have just given birth. They don't seem particularly nurturing and have their puppies hassling them for milk. The puppies have obviously developed sharp new teeth which hurt their mom when they feed...thus, the mommies have HUGE, BULGING titties!! And so, 'lactose baggage' was coined!