Anti-PMSG antibody levels in sheep subjected annually to oestrus synchronisation

Estimation of the long-term consequences on reproduction performance of the oestrus synchronisation treatments that are annually applied to ewes was carried out on nine officially controlled dairy flocks in the Roquefort region of France. A hormonal treatment combining the insertion of a vaginal fluoro-gestone acetate (FGA) sponge for 14 days and the injection of about 500 IU of pregnant mare serum gonadotropin (PMSG) at withdrawal was applied to the ewes in seven of the nine flocks. The ewes in the two other flocks were used as controls. Blood samples were taken from each female just before the treatment (to test for the presence of residual antibodies) and 20 days after the PMSG injection. Anti-PMSG antibody binding rates were calculated for each blood sample. The residual binding rate increased with age and induce negative effects on the following years reproduction performances, i.e., they increased the probability that the ewes would not become pregnant.