Blood flow to uteri of sows during the estrous cycle and early pregnancy: local effect of the conceptus on the uterine blood supply.

Abstract

Uterine blood flow (UBF) of 6 sows was monitored throughout an estrous cycle and the first 30 days of pregnancy using electromagnetic blood flow probes. Probes were placed around both uterine arteries of each sow on Day 12, 13 or 14 of the estrous cycle (first day of estrus = Day 0). The UBF (ml/min) was recorded twice daily for 15 min at 0700 and 1600 h. Values were averaged over both 15 min periods on each day for each artery and considered an estimate of UBF. Blood flow to uteri of nonpregnant sows was highest from Day −5 to estrus and this was followed by a gradual decline during the remainder of the estrous cycle. The pattern of blood flow to uteri of the sows during early pregnancy was similar to that observed during the previous estrous cycle until Day 11 after mating. On Days 12 and 13 of pregnancy, UBF increased (P<0.0l) 3-fold to 4-fold. No corresponding increase in UBF was observed in nonpregnant sows during this 2 day period. By Day 14 of pregnancy, UBF had returned to a level slightly higher than that observed on Day 11, remained relatively constant from Day 14 to 19, then increased (P<0.01) dramatically to Day 30. a second study was conducted using 7 sows made unilaterally pregnant on day 2 postmating (first day of mating = day 0). fertilized ova were flushed from one oviduct and the ipsilateral uterine horn was ligated at the uterine body with silk sutures (nongravid horn). blood flow probes were placed around both uterine arteries and ubf was recorded twice daily. sows were slaughtered on day 16 postmating. five of the 7 sows had embryos and/or embryonic tissue in the nonligated uterine horn (gravid horn) at slaughter. sows in which embryonic tissue was found had higher (p<0.05) blood flow to the gravid compared with the nongravid uterine horn on days 12 and 13 of pregnancy. corpora lutea on the ovary ipsilateral to a gravid uterine horn had higher (p<0.05) progesterone concentrations (±sem) than did corpora lutea on the contralateral ovary (5.45 ± 1.69 vs 2.07 ± 0.49 µg/g luteal tissue).