Effect of Unilateral Ovariectomy at Three Stages of the Estrous Cycle on the Activity of the Remaining Ovary and Pituitary Gland

This experiment was designed .to study follicular development at various days of the estrous cycle in intact gilts for comparison with follicular growth following the removal of surface follicles from the ovaries by electrocautery at different stages of the estrous cycle. Thirty-five Yorkshire-Poland China gilts were divided equally into seven subgroups. Four of the subgroups served as controls and were slaughtered on day-2, -8, -14 or-20 of the estrous cycle (day-0 = first day of estrus), respectively, and three of the subgroups were subjected to follicle-cautery on day-2,-8 or -14 of the estrous cycle, respectively, and were slaughtered 6 days after surgery. The following cyclical variations in follicular development were found in the intact control gilts: (1) the weight of the ovarian fluid increased (P<.05) to day-8, decreased (P<.05) to day-14 and then increased (P<.05) to day-20; (2) the number of small follicles (1 to 2 mm dia.) did not differ significantly among day-2, -8 and -14, but was reduced (P<.number of follicles increased (P<.01) from day-2 to -8, remained approximately the same from day78 to -14 and then decreased (P<.01) to day-20; (4) the number of large follicles (7 to 10 mm dia.) was low throughout the first three stages and then increased (P<.01) at day-20; and (5) the mean diameter of the four largest follicles increased (P<.01) from day-2 to -8, decreased slightly to day-14 and then increased (P<.01) in diameter to day-20. Resuits in the follicle-cautery gilts were: (1) no significant differences in the ovarian endpoints' measured six days following surgery at day-2 or day-8 and (2) fewer (P<.01) small and medium follicles and total number of follicles, but more (P<.01) large follicles and a greater (P<.01) diameter of the four largest follicles at day-20 than at day-8 or day-14. Comparisons between the control and follicle-cautery gilts at the same day of the estrous cycle showed the following:(1) the control gilts had more (P<.01) ovarian fluid than the follicle-cautery gilts at day-8; (2) there were not any significant differences between the control and follicle-cautery gilts in any of the ovarian follicular endpoints at day-14; and (3) the control gilts had more ovarian fluid (P<.05), more small follicles (P<.01) and more extra-large follicles (>10 mm dia., P<.05) but fewer medium follicles (P<.01) than the follicle-cautery gilts at day-20. The particular surface follicles which have the potential to ovulate, appear to start their macroscopically-visible growth between day-8 and -14 of the estrous cycle. (

Section: Follicular Development In the Control Giltssupporting

confidence: 90%

Section: Introductionsupporting

confidence: 80%

Ovarian Follicular Development during the Estrous Cycle in Gilts following Electrocautery of Follicles

Clark

First

Chapman

et al. 1975

“…In 1787, Hunter demonstrated that unilateral ovariectomy (ULO) did not reduce litter size in swine. This phenomenon, known as compensatory ovarian hypertrophy, has been demonstrated in various polytocous (Edgren et al, 1965;Short et al, 1968) and monotocous (Saiduddin et al, 1970;Land, 1973) species. In cycling heifers, ULO resulted in compensatory ovarian hypertrophy and was characterized by an increased number of large follicles (Saiduddin et al,i970); however, the effect of ULO on gonadotropin secretion and follicular development in prepuberal heifers has not been published.…”

Section: Introductionmentioning

confidence: 92%

Effect of Unilateral Ovariectomy and Injection of Bovine Follicular Fluid on Gonadotropin Secretion and Compensatory Ovarian Hypertrophy in Prepuberal Heifers

Smith

1985

A study was conducted to determine whether compensatory ovarian hypertrophy occurred in prepuberal heifers, and if so, could compensatory ovarian hypertrophy be prevented by injecting charcoal-extracted bovine follicular fluid (CFF). An additional objective was to determine the effect of CFF injections on follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations following unilateral ovariectomy (ULO). Thirty-one prepuberal Angus, Hereford, and Angus X Hereford heifers were assigned by weight and breed to the following groups: Control-saline injections (C), unilateral ovariectomy-saline injections (ULO) and unilateral ovariectomy-CFF injections (ULO-CFF). In group C, a sham operation was performed on d 0 and both ovaries were removed on d 7. In groups ULO and ULO-CFF, either the right or left ovary was removed on d 0 and the remaining ovary was removed on d 7. From d 0 to 7, each heifer received an injection (iv, 7 ml/injection) of saline or CFF every 12 h. Jugular blood samples were collected immediately before each saline injection from d 0 to 7 and analyzed for FSH and LH. Unilateral ovariectomy increased ovarian (P less than .08) and follicular fluid (P less than .05) weights compared with groups C and ULO-CFF; however, lyophilized ovarian weight was similar (P greater than .05) for all groups. Injections of CFF blocked the increase in ovarian and follicular fluid weight following ULO. The total number of visible follicles per ovary was similar for all groups; however in the ULO group there was an increase (P less than .01) in those 5 to 6 mm and greater than or equal to 9 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

“…Results from several studies indicate that recruitment of ovarian follicles can occur rapidly in the gilt (Short et al, 1968a;Brinkley and Young, 1969;Clark et al, 1975;Dailey et al, 1975;Dailey et al, 1976) except immediately before ovulation (Hunter et al, 1976;Clark et al, 1982). Likewise, compensatory ovarian hypertrophy does not occur immediately after unilateral ovariectomy (ULO) performed late in an estrous cycle of hamsters (Greenwald, 1962b), guinea pigs (Hermreck and Greenwald, 1964) and rats (Peppler and Greenwald, 1970).…”

Section: Introductionmentioning

confidence: 99%

Factors Affecting Ovarian Compensation after Unilateral Ovariectomy in Gilts

Coleman

Fleming

Dailey

1984

Two experiments were conducted to identify the temporal limits of an ovarian compensatory response after unilateral ovariectomy (ULO) in gilts and to examine ovarian and hormonal factors that might be related to this response. In the first study, all eight gilts that were unilaterally ovariectomized on d 12, 14 or 16 of an estrous cycle and two of four ULO on d 18 had a significant compensatory increase in ovulation rate per ovary compared with controls. Ovulatory compensation failed to occur, however, in two of four and four of four gilts ULO on d 18 or 19 of an estrous cycle, respectively. In the second study, blood samples were collected from 26 gilts beginning on d 14 of an estrous cycle, and animals were assigned to sham-surgery or ULO on d 17, 18 or 19. Ovarian compensation occurred after ULO on all 3 d of surgery in the second study, but most follicles failed to ovulate and formed large luteinized cysts. The ability to compensate was related positively to the number of medium-sized follicles on the intact ovary at the time of ULO, to an increase in concentrations of follicle-stimulating hormone 12 to 18 h after ULO and to the interval from ULO to the preovulatory surge of luteinizing hormone. In a third experiment, interruption of the ovulatory mechanism and development of cystic follicles similar to those observed in the second study were induced simply by physical manipulation of the d 19 preovulatory ovary while contralateral untouched ovaries ovulated normally.