Suppression of testicular function using two dose rates of a reversible water soluble gonadotrophin releasing hormone (GnRH) vaccine in colts

Australian Veterinary Journal - Tập 74 Số 3 - Trang 228-235 - 1996
K. F. Dowsett1, L. M. Knott2, Ugyen Tshewang2, Anne Jackson3, D. A. V. Bodero2, T.E. Trigg4
1Department of Farm Animal Medicine and Production, University of Queensland, New South Wales.
2Department of Farm Animal Medicine and Production, The University of Queensland, Queensland 4072
3Department of Immunology, Sullivan and Nicolaides Pathologists, PO Box 344, Indooroopilty, Queensland 4068
4Peptide Technology Ltd, PO Box 444, Dee Why, New South Wales 2099

Tóm tắt

Objective:To investigate the effect of two dose rates (200 and 400 ng) of a gonadotrophin releasing hormone (GnRH) vaccine on testicular function. Design:A vaccination dose rate experiment. Procedure:Two injections were administered 4 weeks apart to six colts in each treatment group. To maintain immunosuppression until the end of the breeding season, a third injection was given if antibody titres fell below 1000. Results:Effective antibody titres were present for 12 to 27 weeks. Testosterone concentrations decreased from 2.22 to 0.31 nmol/L 6 weeks after primary vaccination. Androstenedione concentrations decreased from 1.78 to 0.28 nmol/L 5 weeks after vaccination. Testosterone and androstenedione concentrations above 0.69 and 0.87 nmol/L were attained 31 to 43 weeks after vaccination. Mean scrotal widths and lengths decreased over 29 weeks from 9.2 cm and 9.7 cm to 6.7 cm and 7.6 cm. At surgical castration these dimensions were 10.1 cm and 11.0 cm. Mean semen characteristics before vaccination and after recovery were: gel‐free volume 16.5 and 13.5 mL, sperm concentration 295.5 times 106 315.6 times 106/mL, total sperm per ejaculate 4041 times 106 4657 times 106 live normal spermatozoa 32% and 60%. Histologically, the testes showed active spermatogenesis. The mean testicular parenchyma weights for the 200 and 400 mg groups were 129.0 g and 109.8 g. Daily sperm production per testis and per gram of testis for the 200 and 400 mg groups were 3.7 times 108 2.8 times 106 2.3 times 108 2.0 times 106. Conclusions:Both dose rates suppressed testicular function. Data showed that the vaccine effects were reversible. Individual immune response was less varied in the 200 mg group. Further work is necessary to achieve a less variable response in the immunosuppression of testicular function.

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Australian Veterinary Journal

Tập 74 Số 3

228-235

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