Colostrum refers to the first secretion from the mammary glands that appear after giving birth. This secretion is normally rich in antibodies. It is also known as colloquially as beestings, bisnings or first milk. Read more from http://en.wikipedia.org/wiki/Colostrum.
Colostrum is the milk that a female mammal produces immediately after the first few hours after giving birth. It contains immunoglobins, antibodies and essential nutrients that are very important for the health and vigor of a newborn.