The amount of immunoglobulin ingested is also a major determinant of final serum immunoglobulin concentration. A practical rule-of-thumb is to feed 5 to 6% of the calf's body weight within the first 6 hours and repeat the feeding when the calf is about 12 hours old. For an 80 pound calf, this will equate to approximately 2 quarts of colostrum per feeding.