Will Falconer, DVM Moderator
Remarkable, but yes, that blood is shared and I guess those antibodies could cross the placental barrier just fine. This is what's called "passive immunity" and it won't likely be long-lived. Much like immunity via colostrum drinking, this gets the newborn a temporary immunity to deal with the world that mom was exposed to. Handiest when you're a farm animal, delivered into a less than hygienic environment.
Thanks, Kat. Pretty interesting.