Yet another study has documented the passive transfer failure rate for dairy calves allowed to nurse from the dam on their own. This is in contrast to hand feeding a known volume of colostrum with a known concentration of antibodies. 
 
The study included 2,500 calves from 50 dairy farms. Cows were Holsteins, Jersey and Holstein-Jersey crosses.  Blood was drawn between 1 and 7 days of age, refrigerated overnight, centrifuged and the serum separated from the clot within 24 hours of collection. The average blood serum total protein level for 2,500 calves as 5.9 g/dL. Successful passive immunity was defined as a blood serum protein level of 5.5 or greater.
 
"Calves that were allowed to suckle their dams showed a 44 percent failure of passive immunity."
 
Can we do a better job when we hand-feed colostrum? One of my clients feeds six quarts of colostrum testing 22 or greater using a Brix refractometer within the first 12 hours of life. As of July 24, 2015 since September 2014 they have tested 756 calves. Ninety-seven percent of these tested at 5.5 or greater.
 
A. Elizondo-Salazar and Others, "Passive Transfer of immunity in dairy heifer calves on Costa Rican dairy farms," Journal of Dairy Science, Vol.98, Suppl.2, Abstract W23.