title: Lambing rate and prolificacy in inseminated hair sheep treated with bovine somatotropin.
abstract: This study evaluated whether the administration of 50 and 100 mg bovine somatotropin (bST) at the start of estrous synchronization and at the time of artificial insemination improves lambing rate and prolificacy in hair sheep. Four hundred eighty adult hair ewes (Pelibuey, Blackbelly, Dorper, Katahdin, and their crosses) were synchronized with intravaginal sponge containing 40 mg of fluorogestone acetate. On the day of sponge insertion, ewes were assigned to three treatments: the bST-100 treatment (n = 156) received 100 mg bST at the start of synchronization (d 0) and at the time of insemination (d 14), the bST-50 treatment (n = 159) received 50 mg bST in the same schedule as the previous group, and the control (n = 165) did not receive any bST. Lambing rate and percentage of multiple births were analyzed using the GENMOD procedure of SAS. Prolificacy data were analyzed using the MIXED procedure of SAS. The IGF-1 and insulin concentrations were analyzed with ANOVA for repeated measures. The bST application did not affect the lambing rate (P = 0.06). The proportion of ewes with multiple births (P = 0.01) and prolificacy (P = 0.04) were higher in the bST-50 (54.3% and 1.57 ± 0.1) than the bST-100 (18.2% and 1.25 ± 0.1) and control (33.3% and 1.28 ± 0.1) groups. The IGF-1 and insulin concentrations were higher (P < 0.05) in the bST-treated groups, but the insulin concentration was higher (P = 0.001) in the bST-100 group than in the bST-50 group. The administration of 50 or 100 mg bST at the start of synchronization and at the time of artificial insemination does not increase lambing rate. However, the dose of 50 mg increased the proportion of multiple births and prolificacy.
authors.affiliation: Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Zacatecas, Carretera Panamericana Zacatecas-Fresnillo Km 31.5, 98500, El Cordovel Enrique Estrada, Zacatecas, México.|Departamento de Ciencias Veterinarias, Instituto de Ciencias Biomédicas, Universidad Autónoma de Ciudad Juárez, Anillo Envolvente del Pronaf y Estocolmo s/n, Zona Pronaf, 35315, Ciudad Juárez, Chihuahua, México.
authors.forename: José Maria
authors.initials: JM
authors.lastname: Carrera-Chávez
authors.affiliation: Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Av. Universidad 3000, 04510, México DF, México.
authors.forename: Joel
authors.initials: J
authors.lastname: Hernández-Cerón
authors.affiliation: Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Zacatecas, Carretera Panamericana Zacatecas-Fresnillo Km 31.5, 98500, El Cordovel Enrique Estrada, Zacatecas, México. arechiga.carlos@gmail.com.
authors.forename: Carlos Fernando
authors.initials: CF
authors.lastname: Aréchiga-Flores
authors.affiliation: Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Zacatecas, Carretera Panamericana Zacatecas-Fresnillo Km 31.5, 98500, El Cordovel Enrique Estrada, Zacatecas, México.
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: López-Carlos
authors.affiliation: Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Zacatecas, Carretera Panamericana Zacatecas-Fresnillo Km 31.5, 98500, El Cordovel Enrique Estrada, Zacatecas, México.
authors.forename: Raúl Renato
authors.initials: RR
authors.lastname: Lozano-Domínguez
authors.affiliation: Departamento de Ciencias Veterinarias, Instituto de Ciencias Biomédicas, Universidad Autónoma de Ciudad Juárez, Anillo Envolvente del Pronaf y Estocolmo s/n, Zona Pronaf, 35315, Ciudad Juárez, Chihuahua, México.
authors.forename: Andrés
authors.initials: A
authors.lastname: Quezada-Casasola
authors.affiliation: Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Zacatecas, Carretera Panamericana Zacatecas-Fresnillo Km 31.5, 98500, El Cordovel Enrique Estrada, Zacatecas, México.
authors.forename: Francisco Guadalupe
authors.initials: FG
authors.lastname: Echavarría-Cháirez
mesh_terms: D000818:Animals; D002417:Cattle; D004334:Drug Administration Schedule; D004971:Estrus / Q000378:metabolism; D004973:Estrus Synchronization; D005260:Female; D003425:Flurogestone Acetate / Q000737:chemistry*; D013006:Growth Hormone / Q000737:chemistry*; D007315:Insemination, Artificial / Q000379:methods* / Q000662:veterinary*; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008460:Meat; D012756:Sheep; D034561:Sheep, Domestic
chemical_list: D007328:Insulin; C073294:growth hormone, bovine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D003425:Flurogestone Acetate
keywords: Artificial insemination; Lambing rate; Prolificacy; Sheep; Somatotropin