title: Preselection of high and low ovulatory responders in sheep multiple ovulation and embryo transfer programs.
abstract: The present study evaluated the feasibility of carrying out an easy-to-handle and cost-efficient test for the preselection of high- and low-ovulatory responder ewes under superovulatory protocols. The test was based on the assessment of the number of ovulations obtained in response to the administration of a single-shot eCG treatment. The predictive value of the test was determined by comparing the number of ovulations with yields obtained in response to a multiple-dose FSH treatment. In addition, the study determined possible effects of follicular status at first FSH dose and their relationship with subsequent ovarian response. A total of 31 Merino ewes received hormonal treatment comprising the administration of 800 IU of eCG at the end of progestative treatment. Twenty-three days later, multiple-dose FSH treatment (80-mg FSH, in six decreasing doses between Days 12 and 14 of a second progestative treatment) was applied to the same ewes. The study showed a significant relationship between the number of corpora lutea obtained in response to eCG treatment with respect to those obtained in response to FSH treatment (r = 0.791; P < 0.05), which resulted in 84% recurrence rate. The number of embryos was greater for high-responder in relation to low-responder ewes (7.2 ± 3.7 and 4.0 ± 3.9, respectively; P < 0.05), whereas rates of recovery and fertilization were similar between groups (P > 0.05). Hence, there was a tendency for a higher mean of grades 1 and 2 embryos in high-responder in relation to low-responder ewes (6.1 ± 3.8 and 3.7 ± 4.0, respectively; P < 0.1). No significant relationship was found between the number of corpora lutea in response to FSH treatment and the number of small and total follicles at first FSH dose (P > 0.05). However, a negative low relationship was found between the presence of large follicles and the ovulation rate in response to FSH treatment (r = -0.361; P < 0.05). In conclusion, the results show the feasibility of carrying out an easy-to-handle and cost-efficient procedure for the preselection of embryo donors. The procedure was based on high recurrence rate between hormonal treatments, which in turn accounts for a distinctive ewe ovulatory response.
authors.affiliation: Laboratorio de Reproducción de Rumiantes Menores, INTA Bariloche, San Carlos de Bariloche, Argentina. Electronic address: brunogalarraga.m@inta.gob.ar.
authors.forename: M
authors.initials: M
authors.lastname: Bruno-Galarraga
authors.affiliation: Laboratorio de Reproducción de Rumiantes Menores, INTA Bariloche, San Carlos de Bariloche, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: Cueto
authors.affiliation: Laboratorio de Reproducción de Rumiantes Menores, INTA Bariloche, San Carlos de Bariloche, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Gibbons
authors.affiliation: Instituto de Ciencias Básicas y Medicina Experimental, Hospital Italiano de Buenos Aires, Argentina.
authors.forename: F
authors.initials: F
authors.lastname: Pereyra-Bonnet
authors.affiliation: Laboratorio de Reproducción de Rumiantes Menores, INTA Bariloche, San Carlos de Bariloche, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: Subiabre
authors.affiliation: Departamento de Reproducción Animal, SGIT-INIA, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: González-Bulnes
mesh_terms: D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D004624:Embryo Transfer / Q000379:methods / Q000662:veterinary*; D004972:Estrus Detection; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006080:Ovarian Follicle / Q000187:drug effects; D010053:Ovary / Q000187:drug effects; D010060:Ovulation / Q000187:drug effects; D012756:Sheep / Q000502:physiology*; D013480:Superovulation
chemical_list: D006063:Chorionic Gonadotropin; D005640:Follicle Stimulating Hormone
keywords: Embryo recovery; Follicular population; Multiple ovulation; Multiple ovulation and embryo transfer