title: Different doses of equine chorionic gonadotropin on ovarian follicular growth and pregnancy rate of suckled Bos taurus beef cows subjected to timed artificial insemination protocol.
abstract: This study evaluated the effect of different doses of eCG (control, 300 or 400 IU) administered at progesterone (P4) device removal in suckled Bos taurus beef cows undergoing a timed artificial insemination (TAI) protocol. A total of 966 cows received a P4 insert and 2.0 mg intramuscular estradiol benzoate at the onset of the synchronization. After 9 days, P4 insert was removed, and 12.5 mg of dinoprost tromethamine and 1 mg of estradiol cypionate were administered, followed by TAI 48 hours later. Then, the cows received one of three treatments as follows: control (n = 323), 300 (n = 326), or 400 IU of eCG (n = 317). A subset (n = 435) of cows in anestrus had their ovaries evaluated using ultrasound at the time of P4 removal and at TAI. Data were analyzed by orthogonal contrasts (C): C1 (eCG effect) and C2 (eCG dose effect). Estrous occurrence (control = 53.7%, 300 IU = 70.6%, and 400 IU = 77.0%) and pregnancy per artificial insemination (control = 29.7%, 300 IU = 44.8%, and 400 IU = 47.6%) were improved by eCG treatment (C1; P = 0.0004 and P < 0.0001, respectively). Furthermore, the cows receiving eCG presented larger follicles at TAI (control = 13.5 ± 0.3 mm, 300 IU = 14.0 ± 0.2 mm, and 400 IU = 15.1 ± 0.3 mm; P < 0.0001; C1). However, there was no effect of eCG dose on any response variables studied (C2; P > 0.15). In conclusion, the eCG treatment administered at the time of P4 removal increased the occurrence of estrus, the larger follicles at TAI, and pregnancy per artificial insemination of suckled B taurus beef cows. Despite the greater occurrence of estrus in noncyclic cows receiving 400 IU of eCG, both eCG doses (300 and 400 IU) were equally efficient to improve pregnancy to artificial insemination.
authors.affiliation: Embryolab - Laboratório de Embriologia Animal, Departamento de Clínica de Grandes Animais-DCGA, Centro de Ciências Rurais - CCR, Universidade Federal Santa Maria (UFSM), Santa Maria RS, Brazil.
authors.forename: G A
authors.initials: GA
authors.lastname: Pessoa
authors.affiliation: Embryolab - Laboratório de Embriologia Animal, Departamento de Clínica de Grandes Animais-DCGA, Centro de Ciências Rurais - CCR, Universidade Federal Santa Maria (UFSM), Santa Maria RS, Brazil.
authors.forename: A P
authors.initials: AP
authors.lastname: Martini
authors.affiliation: Laboratório de Biotecnologia da Reprodução (Biotech), Universidade Federal do Pampa, Uruguaiana, Rio Grande do Sul, Brazil.
authors.forename: G W
authors.initials: GW
authors.lastname: Carloto
authors.affiliation: Núcleo de Pesquisa, Ensino e Extensão em Pecuária (NUPEEC), UFPel, Pelotas, Rio Grande do Sul, Brazil.
authors.forename: M C C
authors.initials: MCC
authors.lastname: Rodrigues
authors.affiliation: Zoetis Indústria de Produtos Veterinários Ltda, São Paulo, São Paulo, Brazil.
authors.forename: I
authors.initials: I
authors.lastname: Claro Júnior
authors.affiliation: Departamento de Reprodução Animal (VRA), FMVZ/USP, São Paulo, São Paulo, Brazil.
authors.forename: P S
authors.initials: PS
authors.lastname: Baruselli
authors.affiliation: Núcleo de Pesquisa, Ensino e Extensão em Pecuária (NUPEEC), UFPel, Pelotas, Rio Grande do Sul, Brazil.
authors.forename: C C
authors.initials: CC
authors.lastname: Brauner
authors.affiliation: Embryolab - Laboratório de Embriologia Animal, Departamento de Clínica de Grandes Animais-DCGA, Centro de Ciências Rurais - CCR, Universidade Federal Santa Maria (UFSM), Santa Maria RS, Brazil.
authors.forename: M I B
authors.initials: MIB
authors.lastname: Rubin
authors.affiliation: Núcleo de Pesquisa, Ensino e Extensão em Pecuária (NUPEEC), UFPel, Pelotas, Rio Grande do Sul, Brazil.
authors.forename: M N
authors.initials: MN
authors.lastname: Corrêa
authors.affiliation: Laboratório de Biotecnologia da Reprodução (Biotech), Universidade Federal do Pampa, Uruguaiana, Rio Grande do Sul, Brazil.
authors.forename: F G
authors.initials: FG
authors.lastname: Leivas
authors.affiliation: Embryolab - Laboratório de Embriologia Animal, Departamento de Clínica de Grandes Animais-DCGA, Centro de Ciências Rurais - CCR, Universidade Federal Santa Maria (UFSM), Santa Maria RS, Brazil; Departamento de Reprodução Animal (VRA), FMVZ/USP, São Paulo, São Paulo, Brazil. Electronic address: mfsvt@yahoo.com.br.
authors.forename: M F
authors.initials: MF
authors.lastname: Sá Filho
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004973:Estrus Synchronization / Q000187:drug effects / Q000379:methods; D005260:Female; D006064:Gonadotropins, Equine / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary; D008297:Male; D009866:Oogenesis / Q000187:drug effects; D006080:Ovarian Follicle / Q000187:drug effects* / Q000502:physiology; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary; D011247:Pregnancy; D018873:Pregnancy Rate
chemical_list: D006063:Chorionic Gonadotropin; D006064:Gonadotropins, Equine
keywords: Bovine; Dominant follicle; Fixed-time artificial insemination; Reproduction; eCG