Effects of suppression by a progesterone-releasing intravaginal device and subsequent induction by GnRH of the preovulatory LH surge on follicular function in PMSG/PG-treated heifers

Abstract

After synchronization of oestrus, normally cyclic heifers (n = 31) received 2500 iu pregnant mares' serum gonadotrophin (PMSG) i.m. and had a progesterone-releasing intravaginal device (PRID) without the oestradiol capsule inserted on day 10 of the oestrous cycle and received 15 mg prostaglandin(PG) i.m. 48 h later. PRIDs were removed 96 h after insertion and 16 heifers received 1.0 mg GnRH i.m. while the controls (n = 15) received 10 ml saline i.m. All heifers were injected with anti-PMSG i.v. 10 later. Peripheral blood concentrations of PMSG, progesterone, oestradiol and LH were compared. Ovaries were collected on death 7 days after the GnRH or saline injection and the number of corpora lutea counted. Heifers were considered to have responded well (> 60 pmol l-1) or poorly (< 60 pmol l-1) to superovulation on the basis of the oestradiol concentration 24 h after PG administration. During PRID treatment, LH concentrations remained at basal values. In the heifers treated with GnRH, a single LH surge occurred 2.3 +/- 0.1 h (SD) after the GnRH injection with a maximum concentration of 14.6 +/- 2.3 (SEM) micrograms l-1 and a duration of 6-8 h. In 12 of the 15 control heifers, LH concentrations remained low (range 0.10-1.94 micrograms l-1) during the 72 h following the saline injection; three controls showed a spontaneous LH surge at 18, 23 and 23 h after the saline injection, respectively, with a maximum concentration of 6.0-12.5 micrograms l-1 and a duration of 10-12 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of delaying the LH surge and altering LH secretion on plasma hormones and embryo production in heifers superstimulated with FSH

“…Thus, despite the continued administration of FSH until GnRH bolus injection, estradiol production in heifers superstimulated with FSH is inhibited in the presence of the progesterone insert. This is in contrast to a previous study (Vos et al 1994a), in which the presence of a progesterone insert did not inhibit the rise in estradiol in heifers superstimulated with eCG. The mechanism of inhibition of estradiol production observed herein is unknown, but likely involves attenuation of LH activity, since estradiol production was restored in the CIDR-3.5d-GnRH-Pulsed group by repeated injections of GnRH.…”

“…The mechanism of inhibition of estradiol production observed herein is unknown, but likely involves attenuation of LH activity, since estradiol production was restored in the CIDR-3.5d-GnRH-Pulsed group by repeated injections of GnRH. The LH activity of eCG may explain the maintenance of estradiol secretion in the study of Vos et al (1994a). In the present study, the absence of a pre-ovulatory rise in estradiol in the CIDR-3.5d heifers did not appear to affect ovulation rate and the number of embryos compared to the SOV group.…”

Bovine Cumulus Cells Protect Maturing Oocytes from Increased Fatty Acid Levels by Massive Intracellular Lipid Storage

“…P4 device removal after 4 days at Day 14 was combined with an injection of gonadotropin releasing hormone (GnRH; 1 mg gonadorelin i.m. Fertagyl, Intervet International BV, Boxmeer, The Netherlands) to induce the LH peak [33]. Ovaries were collected at 22 h after the LH peak, just before ovulation, by ovariectomy through a flank incision under local anesthesia (Alfasan Nederland BV, Woerden, The Netherlands).…”

Consequences of In Vivo Development and Subsequent Culture on Apoptosis, Cell Number, and Blastocyst Formation in Bovine Embryos

“…To obtain embryos at precisely defined times after ovulation, heifers were treated for superovulation using a procedure with a controlled LH surge as described by Vos et al [24] with slight modifications. Clinically healthy, nonlactating Holstein-Friesian heifers were selected from the experimental herd of the Veterinary Faculty of Utrecht University on the basis of cyclicity, as established by measuring progesterone levels in peripheral blood samples taken three times a week for at least 4 wk before the experiment started.…”