The greater absorption of colostral immunoglobulin in neonate calves suckling their dams over bottle-feeding pooled colostrum was studied to determine if age (hours postpartum) at initial feeding, amount of colostrum ingested, or mothering effect of being with the dam were responsible. Rate of absorption and maximum absorption were superior in calves that suckled, regardless of age or amount of colostrum ingested. Though the mothering effect is questionable, there is evidence that something labile is being transferred to the calf in the fresh colostrum, acting as a messenger to stimulate rapid absorptive activity in the intestinal epithelium.