Pooled colostrum from the first three milkings postpartum was used in two trials to determine the effect of abomasal curd forming on absorption of IgG in newborn calves. In Experiment 1, two groups of seven Friesland calves each received 1 h postpartum 1 L of untreated colostrum or colostrum treated with an oxalic acid-sodium hydroxide buffer to prevent coagulation. Calves were not allowed to suckle their dams and received colostrum in teat bottles. The same treatments were applied for Experiment 2, except that eight calves per group were used, and each calf received 2 L colostrum. Blood samples were taken from the jugular vein 6 h postfeeding, and plasma IgG concentration was determined by a radial immunodiffusion technique. Plasma IgG concentration, estimated IgG absorption, and apparent efficiency of absorption 6 h postfeeding for the coagulable and noncoagulable treatments, respectively, were 11.6 and 6.6 mg/ml, 28.1 and 15.8 g/d, and 87.8 and 49.3% for Experiment 1; and 21.2 and 12.9 mg/ml, 48.6 and 34.2 g/d, and 60.8 and 42.8% for Experiment 2. It was concluded that the curd-forming ability of colostrum is an important factor in effective absorption of IgG by calves during the first 6 h postfeeding.