Apparent efficiency of antibody absorption (abbreviated as AEA) is a measure of the movement of antibodies from the gut into the body plasma.
[Quigley, J.D. and J.J. Drewry, "Nutrient and immunity of the noenatal intestine and their relationship to immuniglobulin absorption and disease" Journal of Dairy Science 81:2779-2790]
In a recently published study AEA was compared for colostrum with either a low or high bacteria count.
[Geisinger, S.L. and Others, "Effect of colostrum heat treatment and bacterial population on immunoglobulin G absorption and health of neonatal calves." Journal of Dairy Science, 98:4640-4645. August, 2015.]
For colostrum with low bacteria counts the AEA was approximately thirty-four percent. That is, out of every 100 antibodies fed, about 34 made it into the blood of the calf.
For colostrum with high bacteria counts the AEA was approximately fourteen percent. That is, out of every 100 antibodies fed, only 14 make it into the blood of the calf.
When we compare these transfer rates it is clear that the absorption rate for high bacteria-count colostrum is barely 43% of that for low bacteria-count colostrum - that is well under one-half the transfer rate due to just one factor - bacteria.
Thus, once we have done a good job of collecting clean colostrum the rule of thumb is to either feed it to the calf within 30 minutes of collection or get it chilled to at least 60 F (16C) with 30 minutes in order to suppress the bacteria count.