The use of PGF2α as ovulatory stimulus for timed artificial insemination in cattle

Abstract

The objective of this study was to evaluate the effect of a PGF2α-analogue (PGF) on ovulation and pregnancy rates after timed artificial insemination (TAI) in cattle. In experiment 1, crossbred dual-purpose heifers, in a crossover design (3 × 3), were given an intravaginal progesterone-releasing insert (controlled internal drug release [CIDR]) plus 1 mg estradiol benzoate (EB) intramuscularly (im) and 250 μg of a PGF-analogue im on Day 0. The CIDR inserts were removed 5 days after follicular wave emergence, and the heifers were randomly divided into three treatment groups to receive the following treatments: (1) 1 mg of EB im (EB group, n = 13); (2) 500 μg of PGF im (PG group, n = 13); or (3) saline (control group, n = 13), 24 hours after CIDR removal. Ovulation occurred earlier in EB (69.81 ± 3.23 hours) and PG groups (73.09 ± 3.23 hours) compared with control (83.07 ± 4.6 hours; P = 0.01) after CIDR removal. In experiment 2, pubertal beef heifers (n = 444), 12 to 14 months of age were used. On Day 0, the heifers were given a CIDR insert plus 2 mg EB im. On Day 9, the CIDR was removed and the heifers were given 500 μg of PGF im. Heifers were randomly assigned into one of three treatment groups: (1) 1 mg of EB (EB group; n = 145); (2) 500 μg of PGF (PG group; n = 149), both 24 hours after CIDR removal; or (3) 600 μg of estradiol cypionate (ECP group; n = 150) at CIDR removal. Timed artificial insemination occurred 48 hours after CIDR removal in the ECP group and 54 hours in the PG and EB groups. The percentage of heifers ovulating was higher in the PG group compared with the other groups (P = 0.08). However, the pregnancy rates did not differ among groups (47.6%, 45%, and 46.6%, for EB, PG, and ECP, respectively; P = 0.9). In experiment 3, 224 lactating beef cows, 40 to 50 days postpartum with 2.5 to 3.5 of body condition score were treated similarly as described in experiment 2, except for the ECP group, which was excluded. The treatments were as follows: 1 mg EB (EB group; n = 117) or 500 μg PGF (PG group; n = 107), 24 hours after CIDR removal. The calves were temporarily separated from their dams from Days 9 to 11. No difference was detected on the pregnancy rate between the EB and PG groups (58.1% vs. 47.6%, respectively; P = 0.11). Taken together, the combined results suggested that PGF2α could be successfully used to induce and synchronize ovulation in cattle undergoing TAI, with similar pregnancy rates when compared with other ovulatory stimuli (ECP and EB).

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

“…Although cows treated with EB and PGF ovulated ~20 hours and ~8 hours earlier than the controls, respectively (Table 1), the reduced number of animals used for daily, every 6-hour ultrasound evaluations did not provide sufficient statistical power to detect differences in this outcome variable. In a previous study performed with Girolando heifers, PGF induced ovulation ~73 hours after CIDR removal (Pfeifer et al, 2014) which is in contrast with the current results on the PG group (84 hours).…”

“…Although a previous study also showed the ability of PGF to induce ovulation in TAI protocols for beef cattle (Pfeifer et al, 2014), to the best of our knowledge this is the first report to determine that PGF has a similar action in dairy cows subjected to TAI, using EB-progesterone-based protocols. In contrast, PGF (1) Calculation based on the subset evaluations (n=9 per group); hours from CIDR removal.…”

“…Hence, PGF may have a great potential for being used as an alternative compound to induce ovulation in dairy cows, particularly replacing estradiol. Although the TAI protocol used in this study did not completely remove estradiol, the second EB injection was abolished without decreasing fertility, resulting in a reduction of milk withdrawal, which could be cost-effective for the farmer (Pfeifer et al, 2014).…”

“…(PG group, n=55) or 2 mL of NaCl at 0.9% (control group, n=9). Timed artificial inseminations were performed 52 to 54 hours after CIDR removal in only EB and PG groups (Pfeifer et al, 2014). A single inseminator performed all TAI, and commercial semen straws from a bull with proven fertility were used.…”

“…Furthermore, incomplete luteolysis has been reported as a negative factor that impairs fertility of a TAI protocol . 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).…”