In the cases where immune milk is collected from cows immunized against one or more pathogens, the immunization regimen occurs during the prepartum period of the cow. To put this in perspective relative to the lactation cycle of a cow, a brief reminder of that cycle may be helpful. Depending on the management system used by a farm, most dairy cattle will have their first calf early in their third year, marking the start of their first lactation. The cow will be re-bred about two to three months into lactation. Pregnancy is approximately 280 days. At about 2 months before expected calving date, or approximately 10 months into lactation, milk removal is halted and the cow is given what is called a -dry‖ period. The mammary gland undergoes a process of involution during the early dry period where most residual milk components are broken down and resorbed [81] . The mammary gland begins a redevelopment phase several weeks prior to calving. Colostrum formation occurs in the days leading up to calving, coinciding with the early phase of lactogenesis (initiation of lactation). In the cow, lactogenesis begins shortly prior to calving and extends into the first few days postpartum. Colostrum collected at the first milking of the cow after calving represents the accumulation of colostral products during the days leading up to parturition, including immunoglobulins which are at their highest concentration in the first milking. Concentrations of immunoglobulins then decline rapidly in the subsequent several milkings [82] .