Let colostrum sit at 68F for 2.5 to 3 days. Guess what? Bacteria counts can go up into the millions. Or, just let it sit for 12 hours at 90F. Sky high bacteria counts. When culturing for bacteria these are the plates in a lab that smell to high heaven after 24 hours in the incubator; the lab tech staff knows that they will be "TNTC" (too numerous to count). 
What happens when this "bacteria soup" is fed to a newborn calf?  
Let's see what happened in a trial done at Penn State [S.L. Gelsinger and Others, "Effect of heat treatment and bacterial population of colostrum on passive transfer of IgG." Journal of Dairy Science, E-Suppl 1, p578, #1166]. They did let colostrum sit at 68F for about 3 days.
The research team used a measure of antibody absorption called "Apparent Efficiency of Absorption" that is expressed as a percent of antibodies fed that end up in the calf's blood (Quigley, et al., 1998).
  • Unheated colostrum with low bacteria concentration  - 31%
  • Unheated colostrum with high bacteria concentration - 16%
  • Heat-treated colostrum with low bacteria concentration - - - - - - - - - - - 37%
  • Heated-treated colostrum inoculated with bacteria to get a high count - 14%
Thus, we conclude that high bacteria counts do depress antibody absorption. Resources that might be helpful in reducing bacteria counts can be found at www.calffacts.com. These include a checklist for reducing coliform counts in colostrum (click HERE ) and a colostrum storage checklist (click HERE )