1 Development of field techniques for collection and disinfection of bison semen

Wild bison populations in North America are threatened by genetic isolation and diseases (e.g. brucellosis and tuberculosis). Challenges for species recovery include the development of techniques to effectively collect and disinfect semen under field conditions. Based on successive field collections using different chemical immobilization agents, an apparent difference in the quality of the ejaculate was observed. Under more controlled conditions, Experiment 1 was done to test the effects of two different drug combinations (metetomidine, zolazepam and tiletamine [MZT] vs. thiofentanyl and xylazine [TX]) on the characteristics of the ejaculate. Semen was collected by electroejaculation from four mature wood bison bulls after immobilization (four collections per bull, n = 16 collections). End-points were compared using a Wilcoxon signed-rank test and expressed as median ± SD. Experiment 2 was done to determine the potential deleterious effects of increasing concentrations of antibiotics on sperm characteristics in bison. The addition of antibiotics to the ejaculate is part of a standard protocol for semen intended for use in AI to minimize the risk of disease transmission. For cattle, the National Association of Animal Breeders recommends the addition of 500 μg gentamicin, 100 μg tylosin, 300 μg lincomycin, and 600 μg spectinomycin in 20 µL mL⁻¹ of raw semen. Semen was collected by electroejaculation of mature wood bison bulls (n = 10) physically restrained in a hydraulic chute. Immediately after collection, each ejaculate was divided into four aliquots. To three aliquots, antibiotics were added at the recommended dose, twice the recommended dose, or four times the recommended dose; one aliquot had no antibiotics added. End-points were compared using Welch ANOVA and expressed as median ± SD. Results of Experiment 1 revealed a difference between drug combinations MZT versus TX, respectively, in volume of the ejaculate (6 ± 1.7 mL vs. 3.5 ± 4.8 mL; Z = −3.4; P < 0.01), sperm concentration (402.5 ± 455.4 million mL⁻¹ vs. 27.5 ± 285.7 million mL⁻¹; Z = −3.4; P < 0.01), sperm per ejaculate (2657.5 ± 3136.3 million vs. 106.5 ± 4386.1 million; Z = −3.4; P < 0.01), overall motility (36.8 ± 22.9%l vs. 29.7 ± 9.3%; Z = −3.3; P < 0.01), and progressive motility (19.1 ± 22.9% vs. 11.5 ± 11%; Z = −3.3; P < 0.01). Results of Experiment 2 showed no difference among semen groups in overall sperm motility (88.2 ± 21.5%; P = 0.94), progressive motility (86.1 ± 21.2%; P = 0.95), or the proportion of morphologically normal sperm (87 ± 9.2%; P = 0.96). Based on these findings, a combination of MZT was superior to TX as a chemical immobilization agent to obtain a good-quality ejaculate from bison collected under sedation, and no deleterious effect, dose-related or otherwise, of antibiotics on sperm quality in bison ejaculates was observed.

Research was supported by grants from Genome Canada, Parks Canada, Mitacs, and the Natural Sciences and Engineering Research Council of Canada.