First evaluation of a novel recombinant eCG molecule in ewes reveals a discrepancy between ovulatory response and pregnancy outcome

This study evaluated the reproductive performance and clinical safety of a novel recombinant eCG (r-eCG) in ewes. Two weeks prior to study onset (Day 0: intravaginal progesterone device insertion), 45 ewes were randomly assigned to negative control (NC; no eCG; n=10), positive control (PC; 400IU commercial non-recombinant eCG; n=20), or treatment group (T; 400IU r-eCG; n=15). Ewes were inseminated with fresh-diluted semen (200×10 6 sperm). Ultrasonography assessed follicle count/diameter (days 11, 13), ovulation (day 13), corpus luteum (CL) number/characteristics (day 20), and pregnancy (day 44). Serum progesterone was measured on day 20; Group T underwent clinical/hematological evaluations (days 0, 20, and 44). Estrus signs were more frequent (P<0.01) in T (100%) than NC (50%), while PC (85%) did not differ. Ovulation rates were similar between T (93%) and PC (95%), but higher than NC (50%; P<0.05). On day 13, largest follicle diameter did not differ (P>0.05) among groups; however, fewer follicles > 2 mm occurred in PC than NC and T (P<0.05). CL number was higher in T than PC (2.0±0.3 vs. 1.0±0.0, P<0.01), while NC did not differ (1.0±0.25). Conversely, pregnancy rate was higher (P<0.05) in PC (70%) than T (28.6%) and NC (20%). Among ovulated ewes, progesterone concentration and progesterone/CL ratio did not differ among groups (P=0.92 and P=0.08, respectively). No relevant r-eCG-related clinical or hematological alterations occurred. In conclusion, 400IU r-eCG effectively induces estrus and ovulation without adverse effects; however, the discrepancy between ovulatory response and pregnancy rate underscores the need for further study refinement to improve fertility.