INVESTIGATIONS OF ESTROGEN CONCENTRATIONS IN BLOOD FROM THE JUGULAR-VEIN AND THE CAUDAL VENA-CAVA IN LATE PREGNANT COWS

Catheters were inserted in the caudal vena cava of 14 cows at 260 days of pregnancy. Estimations of total blood oestrogen concentrations wer e made daily on samples obtained from the caudal vena cava and the jug ular vein for 11 days. The concentration of oestrogens in samples from the caudal vena cava was approximately twice that in, samples from th e jugular vein. The concentration increased over the period of the stu dy. The implantation of a catheter in the caudal vena cava would appea r to be useful in the investigation of oestrogens in late pregnant cow s.