Some studies have demonstrated that, when superovulation is induced more than once in the same animal, the response to treatment may be reduced. This reduced response may be related to an increase of anti-gonadotrophin antibodies. The aim of this study was to evaluate the effect of repeated recombinant human (rh) FSH superovulation treatments on the ovulation rate and anti-FSH antibodies production. For this purpose, 34 females were treated i.m. with rhFSH (0.6 mg every 24 h, for 3 days) in order to induce superovulation four consecutive times. Control does were injected with the vehicle at the appropriate time. The interval between the first three treatments was one month; and three months between the third and fourth treatment during which the females were inseminated without superovulation treatment. Ovulation rate was checked by laparoscopy and blood samples were
collected after each treatment. An indirect ELISA was used to detect sera anti-FSH antibodies. The ovulation rate was significantly higher in does treated with rhFSH than in control group. The ovulation rate was significantly higher in does treated for the first time with rhFSH than in those treated two, three, or four times (8.7±1.42, 19.3±1.36, 13.5±1.26, 13.0±1.28, 14.3±1.31 for control and
superovulated females, respectively, P<0.05). On the other hand, results obtained after four consecutives rhFSH treatments indicate that there was a significant difference in immune response of does after the second treatment (P<0.05), none of the treated females presented immune response in the first or second treatment, on the contrary, in the third and forth treatment the 40 to 60% of females presented high antibody levels. The results of the present study clearly demonstrate that repeated rhFSH superovulation treatments in rabbit does induce a immune response and have a negative effect on ovulation rate. Although anti-FSH antibodies induce a decrease in superovulation response, the ovulation rate of females superovulated twice, three and four times was significantly higher than control females. The immune response developed has an important individual variability and may be related with the reproductive response decrease after repeated treatments. Nevertheless, since there were females in which ovulation rate diminished without an increase in sera antibodies, it is clear that reproduction failure after consecutive superovulation treatments can be caused by different reasons, which have to be studied in future
