Objectives were to investigate progesterone concentrations and fertility comparing 2 different intervals from PGF(2α) treatment and induced ovulation in an estrogen-based ovulation synchronization protocol for timed artificial insemination (TAI) or timed embryo transfer (TET) in lactating dairy cows. A total of 1,058 lactating Holstein cows [primiparous (n=371) and multiparous (n=687)], yielding 34.1 ± 0.33 kg of milk/d at various days in milk were randomly assigned to receive treatment with PGF(2α) on either d 7 or 8 of the following protocol: d 0: 2mg of estradiol benzoate + controlled internal drug release device; d 8: controlled internal drug release device removal + 1.0mg of estradiol cypionate; d 10: TAI or d 17: TET. Only cows with a corpus luteum at d 17 received an embryo and all cows received GnRH at TET. Pregnancy diagnoses were performed by detection (transrectal ultrasonography) of an embryo on d 28 or a fetus on d 60. Fertility [pregnancy per artificial insemination (P/AI) or pregnancy per embryo transfer (P/ET)] was affected by breeding technique (AI vs. ET) and time of PGF(2α) treatment (d 7 vs. 8) at the 28-d pregnancy diagnosis for TAI [32.9% (238) vs. 20.6% (168)] and TET cows [47% (243) vs. 40.7% (244)] and at the 60-d pregnancy diagnosis for TAI [30% (238) vs. 19.2% (168)] and TET cows [37.9% (243) vs. 33.5% (244)]. The progesterone (P4) concentration at d 10 altered fertility in TAI cows, with higher P/AI in cows with P4 concentration <0.1 ng/mL compared with cows with P4 concentration ≥ 0.1 ng/mL, and in ET cows, with higher P/ET in cows with P4 concentration <0.22 ng/mL compared with cows with P4 concentration ≥ 0.22 ng/mL. Prostaglandin F(2α) treatment at d 7 increased the percentage of cows with P4 <0.1 ng/mL on d 10 [39.4 (85) vs. 23.2 (54)]. Reducing the period between PGF(2α) and TAI from 72 to 48 h in dairy cows resulted in a clear reduction in fertility in cows bred by TAI and a subtle negative effect in cows that received TET. The earlier PGF(2α) treatment benefits are most likely mediated through gamete transport, fertilization, or early embryo development and a more subtle effect of earlier PGF(2α) treatment that may be mediated through changes in the uterine or hormonal environment that manifests itself after ET on d 7.

The objective was to evaluate the effect of increased progesterone (P4) during preovulatory follicle growth during timed AI (TAI) or timed embryo transfer (TET) protocols. Lactating dairy cows with no CL and low circulating P4 (≤1.0 ng/mL) were submitted to a protocol using one or two intravaginal P4 implants (controlled intravaginal releasing device [CIDRs]), and were bred to TAI or TET. The low P4 cows for this experiment were identified on nine farms, four utilized TAI (n = 326 of 1160 cows examined), and five utilized TET (n = 445 of 1396). All cows were synchronized by insertion of P4 implant(s) (CIDR[s]) at start of protocol (Day -11) and simultaneous treatment with 2 mg of E2-benzoate. After 7 days, cows were treated with PGF (Day -4) and 2 days later treated with 1.0-mg E2-cypionate and CIDR(s) were removed (Day -2). Cows received TAI on Day 0 or TET on Day 7. Cows were randomly assigned to receive either one or two CIDRs on Day -11 until Day -2 (1CIDR vs. 2CIDR). Presence of CL was determined by ultrasound on Day -11 and Day 7 after protocol (to determine ovulation to protocol), P4 concentrations were determined on a subset of cows (Day -11, Day -4, Day 7), and ovulatory follicle diameter was evaluated on Day 0. Pregnancy success (P/AI or P/ET) was evaluated on Days 32 and 60. The 2CIDR treatment increased circulating P4 by Day -4 (1.77 ± 0.23 vs. 2.18 ± 0.24 ng/mL) but had no effect on ovulation at the end of protocol (83.6 vs. 82.6%) or ovulatory follicle diameter (15.6 ± 0.3 vs. 15.3 ± 0.3 mm). If only cows that ovulated to the protocol were included, 1CIDR tended to have lower P/AI than 2CIDR by Day 32 (42.8 vs. 52.6%; P = 0.10) and Day 60 (37.7 vs. 48.1%; P = 0.08) but there was no effect on pregnancy loss. There was an interaction (P = 0.05) between ovulatory follicle diameter and CIDR treatment on P/AI (Day 60). In cows ovulating larger follicles (≥14 mm), 2CIDR treatment increased P/AI compared with 1CIDR (53.3 vs. 34.9%; P = 0.02) but not in cows ovulating small follicles (<14 mm). There was no effect of treatment on P/ET on Day 32 (30.0% vs. 32.0%) or Day 60 (24.7% vs. 25.6%). Thus, these results add evidence to the concept that increased circulating P4 during preovulatory follicle development may improve P/AI, most likely due to improved oocyte quality in cows that ovulate larger follicles, since improvement was only in cows ovulating larger follicles and no effect of preovulatory P4 was observed in cows that received ET.

The objective was to evaluate in vitro embryo production (IVEP) in nonlactating Holstein cows after ovarian superstimulation. Cows were randomly assigned in a crossover design to 1 of 2 groups: control (n=35), which was not synchronized and not treated with hormones before ovum pick-up (OPU), or hormone-treated (n=35), in which wave emergence was synchronized and animals treated with porcine (p)-FSH in the presence of norgestomet before OPU. In the hormone-treated group, all follicles ≥7mm in diameter were aspirated for synchronization of wave emergence and cows received a norgestomet ear implant. After 36h, treatment with p-FSH (6 doses of 40mg each, 12h apart, i.m.) started. Ovum pick-up from follicles >2mm in diameter was performed 44h after the last p-FSH (coasting). Then, IVEP was performed. The total number of cumulus-oocyte complexes recovered (16.0 vs. 20.5±2.2) and number of grades I to III (viable) oocytes (10.7 vs. 12.3±1.6) did not differ between hormone-treated and control groups Additionally, no differences were found in the number of blastocysts per cow per OPU (3.0 vs. 2.6±0.5) or in blastocyst rates (17.1 vs. 12.2±2.4%) between hormone-treated and control, respectively. Thus, in this study, ovarian follicle superstimulation with p-FSH followed by coasting in nonlactating Holstein cows that had synchronization of wave emergence and progestin supplementation did not improve oocyte quality or IVEP compared to no hormonal treatment.

The aim of this study was to determine the association between estrous expression, measured using a breeding indicator and an automated activity monitor (AAM), and the success of embryo collection after superovulation. Holstein heifers (n = 51; 10.5 to 14.5 mo, and 325.0 ± 21.1 kg of body weight) were superovulated (n = 69 events) for the collection of embryos using a protocol based on sequential administration of FSH for follicle superstimulation and GnRH to induce ovulation. Artificial insemination (AI) was performed twice, once at the moment of GnRH administration and again 12 h later, using thawed, sexed semen. Ovaries were scanned via ultrasonography on the day of the first AI to count the total number of preovulatory follicles and 7 d later for the total number of corpora lutea present.

Various programs have been used to synchronize ovulation of a fertile oocyte, accompanied by fixed-time artificial insemination (FTAI). These programs involve a series of hormonal treatments to achieve four physiologic outcomes: 1) synchronize an ovarian follicular wave; 2) optimize conditions for ovulatory follicle development; 3) synchronize corpus luteum (CL) regression; and 4) synchronize ovulation. This manuscript summarizes studies conducted in Brazil with lactating dairy cows that aimed to increase pregnancy rates to E2/P4-based programs.