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Active immunisation of lambs early in life with inhibin can advance puberty and increase ovulation rate but these effects appear not to be mediated through changes in FSH concentrations. The aims of this study were to advance puberty in ewe lambs and determine if increased plasma concentrations of gonadotropins are responsible for the advancement of puberty. Ewe lambs were immunised at 3, 7 and 15 weeks of age against either a synthetic inhibin alpha subunit peptide 1–32 conjugated to human serum albumin (HSA), or an inhibin preparation purified from porcine follicular fluid (porcine monoclonal purified inhibin; pMPI), or HSA alone (control immunogen). Immunisation with inhibin alpha peptide 1–32 produced antibodies which bound iodinated native bovine inhibin and advanced puberty (time of first ovulation) and increased ovulation rate but did not significantly increase plasma FSH concentrations, although LH concentrations were lower (P This study confirms that active immunisation of ewe lambs early in life against inhibin advances puberty via a mechanism which does not significantly increase plasma gonadotrophin concentrations. Immunisation to advance puberty also results in persistent increases in ovulation rates in later breeding seasons.

Studies have shown that follistatin may be involved in the regulation of ovarian development, pregnancy and parturition. The aim of the present study was to measure follistatin levels in maternal plasma and foetal fluids during pregnancy and parturition in sheep. Using a previously described follistatin radioimmunoassay, we found that follistatin in foetal plasma and allantoic fluid was higher in the female than in the male at days 50–75 of gestation. Follistatin concentrations in maternal plasma declined from −9 to −3 h before the completion of lamb delivery, and increased from 21 to 39 h after parturition. These results suggest that follistatin may play a role in femaleness development, and that follistatin may be involved in the mechanism of normal parturition and in regulation of the tissue repair after parturition.

The transition of a primordial follicle to a primary follicle is an early step in folliculogenesis. All female mammals are born with a fixed stock of primordial follicles, and exhaustion of that stock leads to menopause or infertility. Recently, several in vitro studies have indicated that BMP-4, BMP-7, and several other growth factors affect the transition of primordial to primary follicles. The aim of our present study was to investigate role of BMP-4 in this process using passive immunization to investigate the role of BMP-4 in a prepubertal mouse model. After seven days of treatment, the weight of antiBMP-4 treated ovaries was significantly lower than the ovaries from mice treated with nonimmune Ig. The number of primary follicles was lower, and the numbers of primordial follicles were higher in antiBMP-4 treated ovaries compared to control ovaries. Treatment with equine chorionic gonadotrophin (eCG) showed no influence on the effects of antiBMP-4 in the mouse ovary. Thus, the results of our study indicate that in vivo BMP-4 acts as transition factor in transition of primordial to primary follicle.

Charcoal-treated bovine follicular fluid (bFF) given as four 5-ml subcutaneous injections to 13 Merino-Border Leicester ewes around the time of natural luteolysis suppressed (P Plasma FSH at 56–72 h before the LH surge (i.e., at the time of the FSH rebound) was correlated with the subsequent ovulation rate (n=13, r= + 0.73, P

Plasma FSH concentrations were measured in Merino ewes immunized with either an inhibin-enriched preparation from bovine follicular fluid (bFFI) or bovine serum albumin. When compared during the normal oestrous cycle, ewes reimmunized three times with bFFI and which showed increased ovulation rates before the experiment had significantly elevated plasma FSH concentrations on Day 13–14 and at Day 2 of the subsequent cycle. There was a positive correlation (P By contrast, when luteolysis was induced by a prostaglandin analogue the bFFI-immunized ewes had lower plasma FSH concentrations than control ewes immediately before and after the preovulatory LH surge. This decrease was significant in the period 9–21 h after the LH surge (P When the ewes were ovariectomized, the post-castration rise in plasma FSH concentration (but not LH) was delayed for a period of 24 h in bFFI-immunized ewes relative to controls. These experiments show that immunization of ewes with an inhibin-like fraction of bFF does not lead to consistently elevated plasma FSH. However, such ewes have altered feedback regulation leading to differential responses of FSH to prostaglandin-induced luteolysis and to castration.