title: Timing of prostaglandin F2α treatment in an estrogen-based protocol for timed artificial insemination or timed embryo transfer in lactating dairy cows.
abstract: 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.
authors.affiliation: Department of Animal Production, São Paulo State University, Botucatu 18168-000, Brazil.
authors.forename: M H C
authors.initials: MH
authors.lastname: Pereira
authors.forename: C P
authors.initials: CP
authors.lastname: Sanches
authors.forename: T G
authors.initials: TG
authors.lastname: Guida
authors.forename: A D P
authors.initials: AD
authors.lastname: Rodrigues
authors.forename: F L
authors.initials: FL
authors.lastname: Aragon
authors.forename: M B
authors.initials: MB
authors.lastname: Veras
authors.forename: P T
authors.initials: PT
authors.lastname: Borges
authors.forename: M C
authors.initials: MC
authors.lastname: Wiltbank
authors.forename: J L M
authors.initials: JL
authors.lastname: Vasconcelos
mesh_terms: D000818:Animals; D002417:Cattle; D003692:Delayed-Action Preparations; D015237:Dinoprost / Q000008:administration & dosage / Q000494:pharmacology*; D004334:Drug Administration Schedule / Q000662:veterinary; D004624:Embryo Transfer / Q000379:methods / Q000662:veterinary*; D004967:Estrogens / Q000008:administration & dosage / Q000494:pharmacology*; D004972:Estrus Detection; D004973:Estrus Synchronization / Q000187:drug effects; D005260:Female; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D007774:Lactation; D010060:Ovulation / Q000187:drug effects; D011247:Pregnancy / Q000187:drug effects
chemical_list: D003692:Delayed-Action Preparations; D004967:Estrogens; D015237:Dinoprost