The purpose of the study was to determine the changes in serum immunoglobulin G (IgG) levels in lambs fed colostrum and dam milk or cow milk after birth. Twenty newborn Sakiz lambs were used in the study. The lambs born from same ewe were divided into two equal groups. 10 lambs in group 1 (control) were kept together with their dams. The separated lambs (experimental) (n=10) were fed commercial cow milk ad libitum for first 2.5 weeks after which the lambs were fed milk replacer, hay and concentrate feed ad libitum up to 2 months of age. The lambs kept together with their dams were fed dam milk for the first 2.5 weeks and, following this, the lambs were kept together with their dams by day, separated in the evening and fed hay and concentrate feed ad libitum in addition to dam milk up to 2 months of age. Blood samples were collected from the jugular vein of the lambs at 12, 24 and 48 hours and on days 14, 28, 42 to 56 following parturition. Serum IgG levels were higher in group 1 (control) than group 2 (experimental) in hour 42 after parturition (p < 0.001). In group 1, serum IgG levels gradually decreased with the advancing days. In conclusion, separated lambs had generally lower serum IgG levels than lambs kept together with their dams. This may indicate that the inflammatory response of lambs fed colostrum and dam milk is better than in other lambs. The findings in the present study support the recommendation that lambs are protected best against disease when they receive colostrum from sheep in sufficient quantity to achieve a high degree of passive immunoglobulin transfer.