Anti-Müllerian hormone and antral follicle count are more effective for selecting ewes with good potential for in vivo embryo production than the presence of FecG E mutation or eCG pre-selection tests

This study aims to compare four different methods for selecting high responding sheep donors for in vivo embryo production. These methods include a pre-selection eCG test (eCG), antral follicle count (AFC), plasma anti-Müllerian hormone measurement (AMH) and genotyping for the presence of the FecG mutation (a polymorphism in the GDF9 gene associated with increased ovulation rate). Santa Ines ewe lambs (n = 25) underwent superovulation (SOV) with 800 IU equine chorionic gonadotropin (eCG) and the corpus luteum (CL) count was recorded by laparoscopy after eight days. At the D0 , blood samples for AMH and genotyping analysis were collected. Twenty-one days after the end of the eCG test, the same animals underwent SOV with 200 mg of FSH, administered in six decreasing doses, and then naturally mated. Immediately before the beginning of the FSH protocol (D0 ), and at the moment of the first FSH dose (D9 ), the AFC was assessed. Plasma AMH was again determined at the D9 . After each screening process, animals were classified as having a high (HR), or low (LR), potential of response (using specific thresholds for each method). Then, the ewes' response to SOV and embryo yield for each screening method, classified as HR or LR, were compared. Animals classified as HR by AFC (HR ) and by AMH concentration (HR ) at the D9 , produced more viable embryos than those classified as LR and LR (HR 6.2 ± 3.2 vs LR 2.8 ± 3.0 and HR 6.6 ± 3.6 vs LR 3.0 ± 2.9). Pre-selection tests with eCG and different FecG genotypes, either heterozygous (+/E) or wild type (+/+), were unable to discriminate HR or LR animals. A tendency (P = 0.06) to have lower plasma AMH was observed in heterozygous FecG (+/E) ewes. In conclusion, both AFC and plasma AMH can be used to select donor ewes with a higher potential of response for in vivo embryo production.