Synchronization and Superovulation of Boer Goats with PGF2á and GnRH or hCG and Parentage Analysis using Microsatellite Markers

The aim of the first investigation was to devise an efficient protocol for getting a satisfactory embryo yield accomplished by combining the recently established ovsynch protocol with pFSH superovulatory treatment. Furthermore, the intention was to minimize the incidence of premature luteal regression frequently encountered in superovulated goats by substituting hCG for GnRH. A total of 51 pluriparous Boer goat does, 2-6 years of age, was subjected to superovulatory treatment and, thereafter, randomly allocated to one of three treatment groups. The does of Group 1 were subjected to an im injection of 0.004 mg of the GnRH analog Buserelin (Receptal®) 18 hours after the superovulatory treatment; does of Group 2 received 500 IU hCG (Chorulon®) and does of Group 3, 1 mL sterile physiological saline solution. Blood samples, collected every 2 h from 1 h before until 42 h after treatment, were analyzed for plasma LH concentration. With the intention to exactly determine ovulationtime, in a subsample of each group ovaries were scanned ultrasonically at 2 hour intervals from 18 hours after the ovulation inducting treatment until after ovulation had taken place. Estrous does were mated and embryos were flushed non-surgically 6 or 8 d after the last mating, depending on whether morulae or blastocysts were to be collected. In GnRH-treated does the LH surge was tightly synchronized; it commenced 1.0 (SEM 0.03) h after treatment. In the hCG- and saline treated groups it commenced 11.8 (SEM 0.5) hours and 14.9 (SEM 1.2) hours after treatment, respectively (P<0.05). The duration of the LH surge was 7.2 (SEM 0.6) hours for the GnRH group, which was significantly shorter than the 11.2 (SEM 0.8) hours for the hCG- and 12.1 (SEM 0.6) hours for the NaCl group (P<0.05). Ovulation was synchronized most effectively with GnRH. With regard to number of transferable embryos (3.2 (SEM 1.2) for the GnRH-, 1.9 (SEM 1.0) for the hCG- and 4.6 (SEM 1.3) for the NaCl group) there were no significant differences. After GnRH and hCG treatment the incidence of corpus luteum insufficiency amounted to 100% and 88%, respectively; after saline treatment it was 56%, which is significantly less (P<0.01), though still substantial. Application of ear implants compensating premature luteal regression resulted in a substantial increased in number of transferable embryos (P<0.05). This study indicates that both GnRH and hCG are suited for synchronizing ovulation in does superovulated in connection with an ovsynch protocol, permitting fixed-time insemination. GnRH, however, was more effective in synchronizing groups of does. The expected reduction in the incidence of luteal insufficiency when substituting hCG for GnRH did not materialize. Only when luteal insufficiency was compensated by providing the does with norgestomet-releasing ear implants, a modest yield of transferable embryos was accomplished.The second investigation addresses the pharmacokinetics of human chorionic gonadotropin (hCG) administered as a single im injection as ovulation inducing agent in the context of superovulation treatment. Nine pluriparous Boer goat does, 2 to 6 years of age, received a single im injection of 500 IU hCG (Chorulon®) 18 h after the end of superovulatory FSH-treatment. Blood samples were drawn two-hourly until 22 hours after hCG administration, thereafter at 26, 32, 38, 42, 66, 90 and 114 h. Plasma hCG concentration was assessed by electro-chemiluminescence immunoassay. Lag time (0.4, SEM 0.1) h, absorption rate constant (0.34, SEM 0.002) h and absorption half life (2.7, SEM 0.5) h, elimination rate constant (0.02, SEM 0.002) h, biological half life (39.4, SEM 5.1) h and apparent volume of distribution (16.9, SEM 4.3) L were calculated as pharmacokinetical parameters of hCG. The hCG curve was characterized by an absorption phase of 11.6 h (SEM 1.8) h and an elimination phase of 70.0 h (SEM 9.8). Considerable individual variation was found in both bioavailability and pharmacokinetical parameters. Biological half life was correlated with peak concentration (r=-0.76), absorption rate constant (r=-0.78) and elimination rate constant (r=-0.87). These results indicate that, following intramuscular administration, hCG is rapidly absorbed, whereas clearance occurs rather gradually, with considerable individual variation in bioavailability and pharmacokinetical parameters.Parentage testing of 13 ET kids using 13 microsatellite markers originally isolated from sheep and goats was done in the third study. In addition, means for expected and observed heterozygosity, number of alleles per locus, effective number of alleles, inbreeding coefficient, polymorphic information content and exclusion probabilities were calculated for 80 unrelated individuals. Four loci (McM527, OarFCB20, BM1258 and INRA0132) deviated significantly (p<0.01) from the Hardy-Weinberg equilibrium; 69% of the loci were highly polymorphic with an average number of 7.46 alleles per locus. The inbreeding coefficient was 0.178, the average expected heterozygosity 0.632 and the mean polymorphic information content 0.591. Considering all loci, the probability of excluding two putative parents was 99.99974% and the probability of identity was instead 4.9×10-11. Paternities of 13 kids were resolved with an estimated pedigree error rate of 15.4%. Mismatching of alleles in at least 4 microsatellite loci led to the exclusion of paternity. Dropping of loci with (PIC) values less than 0.4 did not affect the effectiveness of other markers to distinguish individuals. From the results it may be concluded that the investigated set of 13 loci may indeed serve as a suitable tool for herd management, enabling confirmation of progeny records prior to selection of breeding animals.