The puppy, born without immunoglobulins G (IgG), acquires a passive systemic immunity thanks to colostrum intake during the two first days of life. The quality of passive immune transfer (i.e. blood IgG concentration at two days of age), highly variable between litters and between puppies within litters, depends mainly on the time elapsed between birth and ingestion of colostrum, with limited influence of colostrum IgG concentration. Deficit in passive immune transfer, impacting puppy's health and neonatal mortality rate, can be indirectly diagnosed through blood gamma-glutamyltransferases assay and evaluation of growth rate over the two first days of life. In the absence of maternal colostrum, few homo- and heterospecific immune sources are available and canine colostrum banking remains the optimal solution. Whereas passive immune transfer is crucial for survival during the neonatal period, it later interferes with response to vaccination. In addition to systemic passive immune transfer, maternal antibodies (mainly IgA) would provide local (digestive) immunity, ensuring mid-term protection of the puppies' gut together with probably long term training of the digestive immune system. Highlights: • As in farm animals, deficit in passive immune transfer is associated in puppies with a higher risk of neonatal mortality. • Intestinal barrier is closed after 12–16 hours of life in puppies. • Time of colostrum ingestion is the major determinant of passive immune transfer, rather than colostral IgG concentration. • Banking of colostrum collected between 24 and 48 hours of life should be encouraged. • Lactogenic immune transfer is not only systemic but also local, providing protection of the digestive tract.