Conventional thinking has maintained that colostrum -- the first mammary secretion following parturition -- is important because it provides the offspring with important immunoglobulins involved in passive immunity. However, its role may be more than that, according to Mike Van Amburg of Cornell University leading off the MILK Symposium at the JAM2013 meeting in Indianapolis, Ind.
Colostrum also contains bioactive factors other than immunoglobulins that may be more important, Van Amburg said, explaining that colostrum is a "tool of the mother to support offspring to begin extra-uterine life." There is a long list of bioactives in colostrum that are just being discovered and explored.
He then discussed the "lactocrine hypothesis" that is defined as maternal programming extended beyond the uterine environment through ingestion of milk-borne morphological factors. A key example of this theory is the relaxin compound in swine in which relaxin activates the estrogen receptor in young gilts that turns on uterine growth and tissue function.
These biofactors appear to affect how a calf utilizes glucose by changing binding sites of key hormones. Van Amburg said calves' glucose status is improved in colostrum-fed calves because colostrum stimulates glucose absorption but not endogenous glucose production.
There may be long-term effects of these colostral bioactives, he said, such as effects on growth rate, feed efficiency and future milk production.
In a follow-up presentation, Dr. Tom McFadden of the University of Missouri said research into these bioactive compounds keeps "getting more and more complex," noting that they often function as signalling factors and such signalling requires both a transmitter and reciever.