SUPEROVULATION AND EMBRYO COLLECTION IN WOOD BISON (Bison bison athabascae): TOOLS TO PRODUCE DISEASE-FREE EMBRYOS

Reclamation of Canada’s threatened wood bison (Bison bison athabascae) herd is complicated by cattle diseases. As part of an overall goal to conserve bison genetics, five studies were conducted to develop or adapting present reproductive technologies to produce disease-free in vivo-derived wood bison embryos. In Chapter 4, the efficacy of pLH and hCG for inducing ovulation and whether the effect was related to the size of the dominant follicle at the time of treatment was examined in wood bison during the anovulatory season . Ovulation rate with hCG (94%) was nearly two times greater than with pLH (54%), and bison with a growing follicle of ≥10 mm had a greater ovulatory response than those of 8-9 mm. In Chapter 5, the efficacy of pLH and hCG after superstimulation with single or two doses (48 hours apart) of FSH diluted in 0.5% hyaluronan was determined in wood bison. A greater superovulatory ovarian response was found in cows treated with hCG vs. LH during the anovulatory and ovulatory seasons (6.6 vs. 2.8 and 6.3 vs. 3.8 corpora lutea respectively). In addition, dividing the dose of FSH two resulted in greater superovulatory response in wood bison. However, the number of corpora lutea was still lower than expected as compared to cattle using the same two dose method of superovulation (15 corpora lutea; Tribulo et al., 2012). Therefore, in Chapter 6, the effect of the addition of a low dose of eCG at the end of the superstimulation protocol on ovarian response and embryo quality was examined. Although the number of ova/embryos recovered was higher in this study when compared with previous reports in wood bison, no effect of eCG on the number of corpora lutea and embryo quality was found. In Chapters 5 and 6, the effect of exogenous progesterone on embryo quality in wood bison during the anovulatory season was evaluated. We found that progesterone did not improve the number of freezable embryos in either study. In Chapter 7, the effect of lengthening of FSH treatment protocol on superovulatory response and embryo quality during the ovulatory and anovulatory seasons was examined. There was no effect of lengthening the FSH treatment protocol on ovarian response and embryo quality during the anovulatory season. However, embryo quality and ovulation rate were increased by the lengthened treatment protocol during the ovulatory season. Additionally, more freezable embryos (Grades 1 and 2) were obtained during the ovulatory season (1.8 embryos) vs. the anovulatory season (0.3 embryos). Overall, results confirm that superovulation can be performed in wood bison throughout the year, but a higher number of freezable embryos were obtained during the ovulatory season. The final chapter (Chapter 8) focused in the production of disease-free embryos in wood bison. Following superovulation, in vivo-derived wood bison embryos were exposed in vitro to Brucella abortus biovar 1. After incubation, embryos were submitted to the 10-step washing procedures recommended by the IETS to remove the pathogen. When the washing medium contained antibiotics, 100% Brucella-free embryos were obtained. These findings validate the washing procedures for the production of Brucella-free embryos in wood bison