The effect of pregnant mare serum gonadotrophin and human chorionic gonadotrophin on ovulation and on fertility in the ewe

Abstract

An experiment involving 300 cyclic Merino ewes and designed to study the effects of pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (HCG) on ovulation and subsequent fertility is described. PMSG (750 i.u.) was given on the 12th day of the oestrous cycle and HCG (400 and 800 i.u.) was injected intravenously within 3 hr of the onset of oestrus. PMSG induced multiple ovulation and hastened the time of ovulation in relation to the onset of oestrus by 2-3 hr, but did not enhance the precision of the time of ovulation. HCG had no effect upon the time of ovulation but did increase the proportion of follicles which ruptured. Neither PMSG nor HCG, alone or in combination, adversely affected fertility. In fact, HCG increased the proportion of ewes which lambed. Both PMSG and HCG increased the incidence of multiple births. The effect of PMSG on the incidence of multiple births was a direct reflection of its ability to induce multiple ovulation. HCG given alone, or after PMSG increased the incidence of multiple births but its effect was less marked than that of PMSG, and unlike that of PMSG the effect of HCG did not appear to be solely due to an increase in the number of ovulations.

The Effects of Short or Long Term FGA Treatment with or without eCG on Reproductive Performance of Ewes Bred Out-of-season

“…Shorter intervals in the eCGtreated groups are attributed to the action of eCG on follicular growth by mediating faster pituitary endocrine responses and estradiol secretion. Treatment with eCG has been shown to advance the intervals to estrus and ovulation in sheep [9,22,23] . These effects are consistent with gonadotropic action of eCG in sheep [23,24] .…”

“…Treatment with eCG has been shown to advance the intervals to estrus and ovulation in sheep [9,22,23] . These effects are consistent with gonadotropic action of eCG in sheep [23,24] . Progesterone profile prior to and following sponge removal: Initial plasma P 4 concentrations on days -12, -4 and on day 0 were basal among groups and averaged 0.1 ± 0.02 ng mL -1 , indicating absence of cyclicity and seasonal anestrus.…”

Intrauterine insemination enhances fertility of frozen semen in superovulated ewes

“…Alternatively, it may be a reflection of earlier ovulation in ewes with higher ovulatory responses to the gonadotrophin. Time of ovulation in relation to progestagen withdrawal has been shown previously to be advanced by treatment with PMSG (Killeen & Moore, 1970) and FSH (Evans & Armstrong, 1984).…”

Effect of Gonadotrophin-Releasing Hormone and Human Chorionic Gonadotrophin on the Response of the Ewe to Pregnant Mare Serum Gonadotrophin

“…The proportion of follicles which rupture has been found to increase when HCG is given within 3 hr after the onset of oestrus in cyclic sheep stimulated with 750 i.u. PMSG in the follicular phase of the cycle (Killeen & Moore, 1970 (Rippel, Moyer, Johnson & Mauer, 1974). These authors concluded that the degree of follicular maturation accounted for these differences because very little follicular growth was evident during anoestrus.…”