Research is indicating that successful transfer of passive immunity enhances disease resistance and performance through the feedlot phase. An example of passive immunity is passing of antibodies from dam to calf via the colostrum (first milk after calving).

Timing of colostrum feeding is important because the absorption of immuno-globulin from colostrum decreases linearly from birth. "Intestinal closure" occurs when large molecules are no longer released into the circulation and this occurs before the specialized absorptive cells are sloughed from the gut epithelium. In calves, closure is virtually complete 24 hours after birth, although efficiency of absorption declines from birth, particularly after 12 hours. This principle of timing of colostrum feeding holds true whether the colostrum is directly from the first milk of the dam or supplied by hand feeding the baby calf previously obtained colostrum.

Provide high risk baby calves (those born to thin, first-calf heifers or calves that endured dystocia) at least 2 quarts of fresh or thawed frozen colostrum within the first six hours of life and another 2 quarts within another 12 hours. This is especially important for those baby calves too weak to nurse naturally.