A look across the immunization protocols used in studies to produce many immune milk products shows considerable variation, especially in the number and timing of immunizations. In those specifically collecting colostrum shortly after calving, multiple immunizations are administered during late pregnancy when the cow would be in the dry period [56] [57] [58] 60, 61, 64, 71, 72, 77, 79, [104] [105] [106] . Mammary secretions then are collected either only at first milking [79] , pooled from the first 4 to 6 milkings [56, 57, 72, 104] , pooled from the first 6 to 10 days after calving [58, 61, 64, 105] , or collected for longer periods into lactation [77] . Other studies have initiated immunizations during the late dry period and then continued vaccinating throughout lactation [50,51,76], or only vaccinating during lactation [107] . Many of these studies used intramuscular or subcutaneous immunization, although some also have incorporated intramammary [58, 79, 105] , or intravenous infusion [61] .