Prostaglandin F2α promotes ovulation in prepubertal heifers

Abstract

The objective was to determine the effects of exogenous prostaglandin F(2α) (PGF), with or without progesterone treatment, on first ovulation in prepubertal heifers. We tested the hypothesis that PGF has a luteolysis-independent ovulatory effect in cattle. Crossbred Angus heifers (12 to 14 mo old, 250 kg body weight, and an average body condition score of 3 out of 5) were examined by transrectal ultrasonography on two occasions, 11 days apart. Heifers in which a CL was not detected at either examination were considered prepubertal. Heifers were assigned randomly to three experimental groups: (1) PG group (N = 14); heifers were treated with a PGF analog (500 μg cloprostenol im) 5 days after the emergence of a spontaneous (i.e., naturally occurring, noninduced) follicular wave; (2) PPG group (N = 12); heifers were given an intravaginal progesterone-releasing insert (CIDR; Pfizer Animal Health, Montreal, QC, Canada), and a follicular wave was induced with 50 mg of progesterone + 2 mg of estradiol benzoate im, and a PGF analog was given at the time of CIDR removal, on day 5 of the follicular wave (on average, 8.6 ± 0.5 days after CIDR insertion); and (3) control group heifers were given no treatment (N = 14). Heifers were examined daily by transrectal ultrasonography from the start of the experiment to confirmation that ovulation had occurred, or to 5 days after PGF injection (PG and PPG groups) or until dominant follicles of the next follicular wave reached 8 mm (control group). The percentage of heifers that ovulated within 10 days after wave emergence was higher in PPG (10/12; 83.3%) and PG (11/14; 78.5%) groups than in control (1/14; 7.1%; P < 0.0001). Ovulations occurred 69.6 ± 6 h and 93.8 ± 5 h after PGF treatment in PPG and in PG groups, respectively, whereas only one heifer in the control group ovulated 96 h after day 5 of follicular wave (P = 0.13). In summary, PGF treatment was associated with ovulation in prepubertal heifers whether or not exogenous progesterone was used as a pretreatment. The hypothesis that PGF will induce ovulation by a luteolysis-independent mechanism was supported.

Different protocols using PGF2α as ovulation inducer in Nelore cows subjected to estradiol-progesterone timed AI based protocols

“…PGF is widely used alone to induce luteolysis and estrus, however, PGF is also used associated to intravaginal progesterone device and estradiol esters in beef cows subjected to timed artificial insemination (TAI) protocols. Previously, intramuscular (im) injection of PGF has also been reported to act as an ovulatory stimulus in prepubertal heifers [3,4]. These studies support the hypothesis that the PGF can induce ovulation of dominant follicle (DF) by an independent mechanism of luteolysis.…”

Prostaglandin F2α or estradiol benzoate to induce ovulation in timed artificially inseminated dairy cows

“…Therefore, the lower ovulatory synchrony observed in the PG group, in comparison to the EB group (Table 1), may be explained by the presence of less developed follicles, which was indicated by the observed low blood flow, regardless of size, which could be less responsive to PGF. Although injectable PGF has been shown to induce ovulation (Leonardi et al, 2012), its mechanism of action still needs to be clarified. A previous report showed an increased frequency of LH release, 6 hours after treatment with a PGF analogue, in anestrous cows (Randel et al, 1996).…”

“…More recently, PGF alone given 24 hours after removal of the progesterone device has successfully induced ovulation in beef cattle undergoing TAI (Pfeifer et al, 2014). Also, previous studies used PGF to induce first ovulation in prepubertal heifers (Pfeifer et al, 2009;Leonardi et al, 2012). However, whether there is a direct action of exogenous PGF on ovulation remains controversial.…”

Comparison of the pregnancy rates and costs per calf born after fixed-time artificial insemination or artificial insemination after estrus detection in Bos indicus heifers

“…As FTAI heifers without a CL were exposed to P 4 and EB treatments prior to the induction of ovulation, this may have increased the likelihood of conception following FTAI. A small proportion of heifers in the EDAI group with no CL may have ovulated in response to the PGF 2α treatment via a luteolysis independent mechanism, but not to the degree of heifers treated with P 4 and EB [21].…”