Immunoneutralization with a monoclonal antibody attenuates the superstimulatory effects of PMSG on endocrine and ovarian responses in red deer (Cervus elaphus)

Superovulation has proved to be a problematic part of embryo transfer in red deer as in other domestic ruminants. Use of PMSG in red deer hinds has been associated with disturbance of follicular development and the endocrine environment. In this study, the effects of PMSG neutralization with a monoclonal antibody on the ovulation rate and the associated LH surge were investigated. Thirty mature hinds were treated during the breeding season with intravaginal progesterone impregnated CIDR devices and divided into 6 treatment groups. Group 1 received no further treatment and served as controls. All other groups were treated with 1200 IU PMSG at -72 h (CIDR withdrawal = time 0). Group 2 received no further treatment. Groups 3 through 6 received a single intravenous injection of a monoclonal antibody to PMSG at -72, 0, 12 and 24 h respectively. Blood samples were taken throughout the experiment and for a 72 h intensive sampling period following CIDR device withdrawal and analyzed for progesterone and LH, respectively. Ovarian response was assessed at laparoscopy on Day 7. The proportion of animals with more than 1 corpus luteum was higher in PMSG-only and +24 h groups than in control, -72, 0 and +12 h groups (P < 0.05). Compared with the PMSG-only treated animals, ovulation rate in PMSG-treated hinds was reduced following treatment with the antibody at -72, 0 and +12 h (P < 0.05) and the number of large Graafian follicles was reduced in all antibody-treated groups. The incidence of a LH surge was lower in the 0 and +12 h than in the PMSG-only and +24 h groups (P < 0.05). Peak progesterone concentrations in hinds treated with PMSG only and antibody at +24 h were higher than in hinds of the other treatment groups (P < 0.05). Two hinds treated with PMSG alone underwent premature luteal regression, evinced by a sharp decline in progesterone after Day 7. These results suggest that passive immunization neutralizes the biological action of PMSG in red deer, and may provide a means of overcoming some of the adverse effects of the hormone. However, the timing of the antibody treatment is crucial to ensure lack of interference of with the endogenous LH surge and subsequent ovulation.