REPEATED SUPEROVULATION FOLLOWING ADMINISTRATION OF EXOGENOUS GONADOTROPHINS IN DUTCH-BELTED RABBITS

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Abstract
Repeated superovulation and in vivo collection of ova were carried out with 30 does divided into 3 groups of 10 does each. One group received FSH-LH [follicle-stimulating hormone-luteinizing hormone], a 2nd group received PMSG-HGG [pregnant mare''s serum gonadotropin-human chorionic gonadotropin] and the controls received only LH. Injections of FSH-LH at 3 16-week intervals followed by one 8-week interval resulted in 46.5, 35.4, 25.2 and 18.0 ovulation points/doe. This decrease with time was significant (P < 0.05). Corresponding values for the PMSG-HCG group which, however, received FSH-LH for the final superovulation were 13.6, 5.7, 6.2 and 20.3. The LH controls averaged 7.8, 7.0, 5.1 and 5.6 Ovulation points. Overall treatment differences were highly significant (P < 0.005). From the 1920 ovulation points 1593 ova (83%) were recovered, of which 83.1% were cleaved. Young born from unrecovered ova accounted for 3.1%. Control kindlings by the same does at regular periods resulted in normal litter size but in fewer does kindling as the experiment progressed. Results of 2 bio-assays for antihormones suggested that this decrease was due to hormonal refractoriness which was most pronounced in the PMSG-HCG group.