Catheterization of the caudal vena cava via the lateral saphenous vein in the ewe, cow, and gilt: an alternative to utero-ovarian and medial coccygeal vein catheters.

Current methods for obtaining venous blood from the reproductive organs of livestock often have a low rate of success or involve intensive surgical procedures that may impair ovarian function. Therefore, the caudal vena cava was catheterized via the lateral saphenous vein to determine the feasibility of using this method for chronic sampling of blood draining from the reproductive organs of ewes (n = 6), cows (n = 6), and gilts (n = 7). Blood samples were collected at 2-cm (ewes and gilts) or 5-cm (cows) intervals during insertion of catheters. Correct placement, defined as the position at which plasma concentrations of progesterone or estrogen were at least threefold greater than in jugular venous plasma, varied among species and among animals within species. It seemed, however, that a majority of catheters would be placed correctly if secured at 48 to 52 cm in ewes, 52 cm in gilts, and 90 to 100 cm in cows. Saphenous vein catheters were secured for sequential sampling of vena caval blood during the follicular phase of ewes (n = 25), cows (n = 4), and gilts (n = 5). Catheters remained patent for the duration of sampling in all individuals. Concentrations of estrogen in jugular and vena caval plasma were correlated (ewe P less than .0003; cow P less than .0001; gilt P less than .0001). Profiles of progesterone and estrogen revealed an episodic pattern of secretion in vena caval but not jugular plasma. Catheterization of the vena cava via the saphenous vein is a relatively simple and noninvasive method for obtaining blood containing uterine and ovarian hormones before their metabolism.