Blood flow, steroid secretion and nutrient uptake of the gravid uterus during the periparturient period in sows.

Blood flow to one uterine horn of six Yorkshire sows was measured daily from d-22 to 0 (d of parturition) using an electromagnetic blood flow transducer surgically implanted around the middle uterine artery. Immediately after measurement of uterine arterial blood flow (UABF), samples of femoral arterial (FA) and uterine venous (UV) blood were collected via indwelling catheters and concentrations of progesterone, estrone and estradiol-17 beta, oxygen, glucose, total alpha-amino acid N and urea N were determined. Throughout the experimental period, sows were maintained in farrowing stalls. Surgical procedures used in this study had no effect on length of gestation, litter size, number of live piglets born or average weight of live piglets when compared with noninstrumented littermate controls. The UABF remained constant from d-22 through -1, then declined dramatically on the day of parturition with delivery of the fetuses and placentae. Concentration of progesterone in FA and UV blood of sows remained constant from d-22 to -3, but was higher (P less than .01) in FA (12.68 +/- .48 ng/ml) than in UV (7.56 +/- .20 ng/ml) blood. Progesterone concentrations in FA and UV blood began to decline 2 d before parturition to reach low levels on d 1. Estrone and estradiol-17 beta concentrations were greater (P less than .01) in UV than in FA blood, and increased progressively from d -22 to reach peak levels on d -4 through -1 which averaged 7,245 +/- 655 and 1,001 +/- 88 pg/ml in UV blood and 3,923 +/- 157 and 547 +/- 35 pg/ml in FA blood, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)