Stanniocalcin-1 is a hormone that possesses both paracrine and endocrine functions and has recently been identified in mammals. While paracrine functions have been determined for several organs, the role of circulating stanniocalcin-1 in cattle is still unclear but, observations in mice and cows suggest that stanniocalcin-1 plays a role in both gestation and lactation. The changes in serum stanniocalcin-1 content in different physiological states have never been evaluated in ruminants. We measured stanniocalcin-1 levels in sera from cattle ranging in age from post-weaned calves to 17-month-old heifers and in sera from cows during lactation and pregnancy. Our results indicate that the blood concentration of stanniocalcin-1 is increased by pregnancy, but not by lactation. The highest levels of stanniocalcin-1 were found in young calves and during the non-lactating period preceding calving. This suggests that stanniocalcin-1 is important for gestation and the preparation of the mammary gland for lactation.