Subtotal Hysterectomy and Ovarian Function in Gilts¹²

This investigation deals with ovarian function in gilts following subtotal hysterectomy during the luteal phase of the cycle. In 7 groups of 5 gilts per group the following parts of the uteri remained in the animals: Group 1, posterior half of cervix; Group 2, body and cervix; Group 3, anterior one-fourth of right horn and posterior half of cervix; Group 4, anterior half of right horn and posterior half of cervix; Group 5, posterior half of right horn including body and cervix; Group 6, anterior halves of right and left horns and posterior half of cervix; and Group 7, sham operations. Nine of 10 gilts in Groups 1 and 2 did not show estrus during a 120-day period following the estrus prior to experimental treatment. Three of 5 gilts in Group 3 did not return to heat during a 70 day period following the estrus prior to surgery. All gilts in Groups 4, 5 and 6 had average estrous cycle intervals of 25 days as compared to 21 days for the same animals prior to hysterectomy. The sham-operated gilts in Group 7 had average estrous cycle intervals of 21 days. These findings suggest that retrogressive transformation of active corpora lutea into corpora albicantia during non-fertile cycles is dependent upon a stimulus from the uterine horns. Persisting corpora lutea (marked) and no heats were observed in gilts in which corrosives and irritants were injected into the lumen of the right uterine horn and body during the luteal phase of the cycle. The left horn was removed. FSH activity was significantly lower (P < 0.05) 2 days after the onset of estrus than at any other stage of the cycle or pregnancy investigated. Fifty days after removal of the uterus FSH activity was significantly lower (P <0.05) than 25 or 110 days after surgery. Differences in LH activity were not statistically significant at any of the stages investigated. Lactogenic hormone potency increased during the cycle and advancing stages of pregnancy. Following removal of the uterus, the quantity of this hormone was greater than during pregnancy. There was a marked decrease in the progesterone concentration in the corpus luteum 110 days after subtotal hysterectomy. In vitro synthesis of this hormone by luteal tissue was observed 25, 50 and 110 days after removal of the uterus.