Intestinal transmission of macromolecules in newborn dairy calves of different ages at first feeding.

Four groups of eight newborn calves were used to study the intestinal transmission of colostral immunoglobulin from the intestinal lumen to the blood circulation. The first feed was given one, eight, 16 or 24 hours after birth. Thereafter, three feeds were given with eight hour intervals. All feeds were from the same pool of colostrum and the amount fed each time corresponded to 3 per cent of the calves birthweight. To estimate the transmission of macromolecules in each feed four different macromolecules were used as markers. For the first feed, the marker was bovine IgG, in the second FITC-dextran, in the third ovalbumin and in the fourth human serum albumin. Blood samples were taken eight hours after each feed and at one week old. There were no differences in transmission for the first feed although the calves varied in age between one and 24 hours, but in the second, third and fourth feeds the calves that received a first feed at one hour old, transmitted significantly more of the marker molecules than did the other three groups. The substantial transmission of macromolecules at the first feed in all four groups indicates that a base level of transmission capacity is maintained during the first 24 hours or longer and that, under certain conditions, acceptable passive immunisation is possible in calves given their first colostrum as late as 24 hours after birth.