title: 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).
authors.affiliation: Embrapa, Brazilian Agricultural Research Corporation, Porto Velho, Rondônia, Brazil. Electronic address: luiz.pfeifer@embrapa.br.
authors.forename: L F M
authors.initials: LF
authors.lastname: Pfeifer
authors.affiliation: Universidade Federal de Santa Maria, Departamento de Clínica de Grandes Animais, Embryolab, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: C E P
authors.initials: CE
authors.lastname: Leonardi
authors.affiliation: Universidade Federal de Rondônia, Porto Velho, Rondônia, Brazil.
authors.forename: N A
authors.initials: NA
authors.lastname: Castro
authors.affiliation: Embrapa, Brazilian Agricultural Research Corporation, Juiz de Fora, Minas Gerais, Brazil.
authors.forename: J H M
authors.initials: JH
authors.lastname: Viana
authors.affiliation: Embrapa, Brazilian Agricultural Research Corporation, Juiz de Fora, Minas Gerais, Brazil.
authors.forename: L G B
authors.initials: LG
authors.lastname: Siqueira
authors.affiliation: Granjas Quatro irmãos, Rio Grande, Rio Grande do Sul, Brazil.
authors.forename: E M
authors.initials: EM
authors.lastname: Castilho
authors.affiliation: Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Singh
authors.affiliation: Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil.
authors.forename: R H
authors.initials: RH
authors.lastname: Krusser
authors.affiliation: Universidade Federal de Santa Maria, Departamento de Clínica de Grandes Animais, Embryolab, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: M I B
authors.initials: MI
authors.lastname: Rubin
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D001938:Brazil; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000000981:diagnostic imaging; D018592:Cross-Over Studies; D015237:Dinoprost / Q000494:pharmacology*; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives; D004973:Estrus Synchronization / Q000379:methods; D005260:Female; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D007774:Lactation; D006080:Ovarian Follicle / Q000000981:diagnostic imaging; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000008:administration & dosage; D013997:Time Factors; D014463:Ultrasonography; D014599:Uterus / Q000000981:diagnostic imaging
chemical_list: C074283:estradiol 3-benzoate; D011374:Progesterone; D004958:Estradiol; D015237:Dinoprost
keywords: Cattle; Ovulation; PGF; Pregnancy; Timed artificial insemination