title: Ovulation synchronization with estradiol benzoate or GnRH in a timed artificial insemination protocol in buffalo cows and heifers during the nonbreeding season.
abstract: The aim of this study was to compare estradiol benzoate (EB) and GnRH for the induction of ovulation in a TAI protocol in buffalo during the nonbreeding season. In experiment 1, 141 buffaloes (56 cows and 85 heifers) received an intravaginal P4 device (1.0 g) plus EB (2.0-mg, intramuscular [im]) at random stage of the estrous cycle (Day 0). On Day 9, the P4 device was removed, and buffaloes were given PGF2α(0.53-mg im sodium cloprostenol) plus eCG (400-IU im). Buffaloes were then randomly allocated to one of three groups and treated as follows: EB24 (n = 47), EB (1.0 mg im) 24 hours after P4 device removal; EB36 (n = 50), EB 36 hours after P4 device removal; GnRH48 (n = 44), GnRH (10 μg im buserelin acetate) 48 hours after P4 device removal. Ultrasound examinations were performed on Day 0 to ascertain ovarian follicular status, Day 9 to measure follicular diameter, and from Day 11 to Day 14 (every 12 hours for 60 hours) to establish the time of ovulation. There were no significant differences between EB24, EB36, and GnRH48 for diameter of the ovulatory follicle (13.1 ± 0.3, 13.7 ± 0.3, and 13.7 ± 0.3 mm; P = 0.26) and ovulation rate (78.7%, 82.0%, and 84.1%; P = 0.93). When compared with heifers, cows had a greater diameter of the dominant follicle on Day 9 (10.3 ± 0.3 and 8.6 ± 0.2 mm; P = 0.0001), diameter of the ovulatory follicle (14.1 ± 0.3 and 13.1 ± 0.2 mm; P = 0.01), ovulation rate (91.1% and 75.3%; P = 0.02), and interval from P4 device removal to ovulation (76.3 ± 1.3 and 72.5 ± 1.4 hours; P = 0.05). In experiment 2, 511 buffaloes (354 cows and 157 heifers) were assigned to the same treatments described in experiment 1 (EB24, n = 168; EB36, n = 172; and GnRH48, n = 171), and all animals were submitted to timed artificial insemination (TAI) 64 hours after P4 device removal. Pregnancy diagnosis was undertaken 30 days after TAI. There were no significant differences between EB24, EB36, and GnRH48 for pregnancy rate (45.2%, 43.0%, and 49.7%; P = 0.46), and the pregnancy rate did not differ (P = 0.31) for cows (47.5%) and heifers (42.7%). The findings from the two experiments indicated that EB (24 or 36 hours) and GnRH (48 hours) induce comparable follicular responses, ovulation, and pregnancy rates in buffalo cows and heifers. Although there were some differences in the follicular responses between cows and heifers, the pregnancy rate to TAI was nonetheless similar.
authors.affiliation: Unidade de Pesquisa e Desenvolvimento de Registro-Polo Regional do D.S.A. do Vale do Ribeira/APTA, Registro, São Paulo, Brazil. Electronic address: nelcio@apta.sp.gov.br.
authors.forename: N A T
authors.initials: NAT
authors.lastname: Carvalho
authors.affiliation: Departamento de Reprodução Animal, VRA-FMVZ-USP, São Paulo, São Paulo, Brazil.
authors.forename: J G
authors.initials: JG
authors.lastname: Soares
authors.affiliation: EDR/CATI, Registro, São Paulo, Brazil.
authors.forename: D C
authors.initials: DC
authors.lastname: Souza
authors.affiliation: Ourofino Agronegócio, Cravinhos, São Paulo, Brazil.
authors.forename: J R G
authors.initials: JRG
authors.lastname: Maio
authors.affiliation: Departamento de Medicina Veterinária, UFLA, Lavras, Minas Gerais, Brazil.
authors.forename: J N S
authors.initials: JNS
authors.lastname: Sales
authors.affiliation: Fazenda Santa Eliza, Dourado, São Paulo, Brazil.
authors.forename: B
authors.initials: B
authors.lastname: Martins Júnior
authors.affiliation: Fazenda Santa Eliza, Dourado, São Paulo, Brazil.
authors.forename: R C
authors.initials: RC
authors.lastname: Macari
authors.affiliation: School of Life and Environmental Sciences, Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, The University of Sydney, Camden, New South Wales, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: D'Occhio
authors.affiliation: Departamento de Reprodução Animal, VRA-FMVZ-USP, São Paulo, São Paulo, Brazil. Electronic address: barusell@usp.br.
authors.forename: P S
authors.initials: PS
authors.lastname: Baruselli
mesh_terms: D000818:Animals; D002020:Buffaloes / Q000502:physiology*; D002064:Buserelin / Q000008:administration & dosage / Q000494:pharmacology*; D006063:Chorionic Gonadotropin / Q000008:administration & dosage / Q000494:pharmacology*; D003008:Cloprostenol / Q000008:administration & dosage / Q000494:pharmacology*; D004334:Drug Administration Schedule; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary; D010053:Ovary / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology; D012621:Seasons
chemical_list: D006063:Chorionic Gonadotropin; C074283:estradiol 3-benzoate; D003008:Cloprostenol; D011374:Progesterone; D004958:Estradiol; D002064:Buserelin
keywords: Buffalo; Buserelin acetate; Estradiol benzoate; Ovulation synchronization; Timed artificial insemination