These adaptations have several consequences both for the composition of immunoglobulins in colostrum and milk, and for the role of colostrum. Indeed, for animals like rats, mice, dogs and ungulates, uptake of colostrum of adequate quality and sufficient quantity is important for the offspring to boost the systemic immune function in the short term, whereas colostrum consumption in the human infant provides more protection for the gastrointestinal tract (see section 6.3). This is reflected in a lower total immunoglobulin content in human colostrum as compared to colostrum from the other species ( Figure 1 ) [1, 3, 117] . Human colostrum has a low content of IgG (2%), and the IgG required to provide systemic immunity is transferred across the placenta before birth. In contrast, colostral IgG content in many other species is typically greater than 75% of the total immunoglobulin content (Figure 1 ). An additional consequence of different routes of immunoglobulin transmission relates to the changes in relative contents of immunoglobulins that occur in the transition from colostrum to milk within certain species (Figure 1 ). For example, the profile of immunoglobulins in human colostrum is similar to that found in milk, where the IgA level is high in both colostrum and milk (88-90% of total immunoglobulin). This is in contrast to the bovine mammary secretions where the high concentration of IgG in colostrum declines rapidly with successive milkings. For animals like rats, mice, dogs and ungulates, the role of colostrum and milk immunoglobulins is to provide immune protection both systemically and for the gastrointestinal tract, which is reflected in large changes in the profile of immunoglobulins during the transition from colostrum to mature milk ( Figure 1 ). Thus, for many species the proportion of IgA increases between colostrum and milk. [1] ; human and pig [3] ; and horse [117] .