Ovarian compensatory hypertrophy following unilateral ovariectomy in the suckled sow

The effects of unilateral ovariectomy on ovarian compensatory hypertrophy (OCH), endocrine profiles and the pituitary response to gonadotropin releasing hormone (GnRH) were studied in 46 multiparous suckled sows. On d 20 of lactation (d 0 of experiment), sows were subjected to sham ovariectomy (Sham; n = 23) or unilateral ovariectomy (ULO; n = 23). On d 1 (n = 16), 2 (n = 15) or 8 (n = 15) following initial surgery the remaining ovaries in both Sham and ULO sows were removed. Immediately following removal of the remaining ovaries, GnRH (10 micrograms) was administered to each sow. Peripheral blood samples were taken every 10 min for 80 min beginning 20 min prior to GnRH administration. No difference in ovarian weight was observed between ULO and Sham sows until d 8, when ovarian weight was greater (P less than .05) for the remaining ovary from ULO sows (3.96 +/- .21 vs 5.91 +/- .39 g). Ovarian follicular fluid weights from ULO sows were greater (P less than .05) than Sham sows on both d 2 and 8. On d 1, plasma concentrations of follicle stimulating hormone (FSH) were greater (P less than .05) in ULO sows than in Sham sows (2.9 +/- .2 vs 2.1 +/- .1 ng/ml). Plasma FSH concentrations, however, did not differ between Sham and ULO sows on either d 2 or 8. Ovarian venous concentrations of estradiol-17 beta were also greater (P less than .05) in ULO sows compared with Sham sows on d 2 but not d 8.