Effects of season, GnRH administration and lupin supplementation on the ovarian and endocrine responses of merino ewes treated with PMSG and FSH-P to induce superovulation

Abstract

Administration of gonadotrophin releasing hormone (GnRH) 24 h after sponge withdrawal did not affect the numbers of corpora lutea (CL) or persistent large follicles (LF) in ewes superovulated with 400 I.U. pregnant mare serum gonadotrophin and 12 mg follicle stimulating hormone in spring (11.6 +/- 0.9 v. 13.0 +/- 0.9 CL and 0.8 +/- 0.9 v. 0.9 +/- 0.3 LF, for +GnRH and -GnRH ewes, respectively). However, it did increase the ovulatory response of ewes superovulated in autumn (15.8 +/- 1.2 v. 11.8 +/- 1.1 CL). The incidence of ewes with prematurely regressed CL was also greater in autumn than in spring (21/89 v. 5/88). Supplementary feeding with lupin grain in autumn had no effect on numbers of CL but did increase the incidence of ewes with LF (18/48 v. 7/46) and caused a marked reduction in the incidence of ewes with regressed CL (1/44 v. 20/45). For ewes treated in autumn, there were no effects of lupin supplementation or GnRH administration on peak oestradiol-17 beta (E2) or peak luteinizing hormone (LH) levels. However, when peak E2 concentrations in the plasma were adjusted for numbers of preovulatory follicles, higher concentrations were observed for ewes in the +lupin/-GnRH group (12.4 +/- 2.9 pg mL-1) than in other treatment groups (range 4.3 +/- 0.4 to 5.7 +/- 0.3 pg mL-1). Moreover, the time of the LH peak was advanced by both lupin supplementation and GnRH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Incidence of Premature Luteal Regression in Ewes Superovulated with a Single Injection of Follicle-Stimulating Hormone Combined with Equine Chorionic Gonadotropin.

“…Similar results have been reported in ewes [10] and goats [11]. However, prematurely regressed CL has been observed in suprovulated ewes [12][13][14], cows [15] and goats [16][17][18]. Ryan et al [13] reported that the proportion of ewes that ovulated and subsequently had M chorionic gonadotropin (eCG) has been conventionally used for superovulation in ewes [1][2][3][4].…”

“…Jabbour et al [12] and Ryan et al [13] reported that more ewes had regressed CL in autumn (24% and 37%, respectively) than in spring (6% and 21%, respectively). In their reports, 12 or 18 mg pFSH was administered with multiple injections.…”

“…Premature luteal regression has been reported in superovulated ewes [12][13][14]22], and has impaired the yield of normal fertilized embryos. Jabbour et al [12] and Ryan et al [13] reported that more ewes had regressed CL in autumn (24% and 37%, respectively) than in spring (6% and 21%, respectively).…”

“…Numbers of newly formed and regressed CL were recorded for all ewes. CL which were small and pale in morphological appearance, were considered as prematurely regressed CL [12].…”

Effect of exogenous melatonin on the ovary, the embryo and the establishment of pregnancy in sheep

“…Inadequate luteal function has also been reported in superovulated ewes following oestrous synchronization using a dual prostaglandin injection treatment (Trounson et al, 1976;Schiewe et al, 1991). In embryo donor ewes, the incidence of premature luteal regression after a progestagen protocol and superovulation seems to be higher in the seasonal anoestrus than in the breeding season, even at temperate latitudes (Jabbour et al, 1991;Ryan et al, 1991). Corpora lutea from ewes undergoing premature luteolysis have a reduced population of small luteal cells compared to normal corpora lutea (Schiewe et al, 1991).…”