1. Alternatives to castration in horses

2. Why castrate? Aggressive behavior –Sex-related aggression –Dominance Related aggression No distractions at shows –Will perform, with mares, in classes Easier to manage –5 ft vs. 7 ft fencing –Limited areas; can pasture with mares

3. What are some alternatives? Progestin therapy GnRH vaccination

4. Progestins Progestins inhibit Leutenizing Hormone production Results –Reduced Leydig cell activity –Reduced testosterone levels in blood plasma –Reduced ejaculate volume –Reduced libido –Reduced sperm production *Stephen J. Roberts (VT) & Bonnie V. Beaver (TX)

5. Gonadotropin releasing hormone Objective: To investigate the effect of GnRH on testicular function

6. The studies: The First Study Six yearling colts were divided into three groups 1) control 2) subcutaneous & 3) intramuscular vaccination –They were fed to ensure adequate growth throughout study –Vaccinated against tetanus

7. The first study Injections 2 cc of mineral oil based GnRH vaccine The control group: never injected The Subcutaneous group: emulsion on the side of neck Intramuscular group: injection in the neck

8. The first study Measurements and Tests *Jugular vein blood assayed before study for testosterone level and GnRH antibodies *Scrotal diameters and body weights were measured prior to study Body weights and Blood assays Scrotal diameters and testicular lengths Blood samples Antibody Assays Semen Collection and Examination Daily sperm production Testis Histology Morphometric Analysis

9. The Results No weight differences Testosterone levels The treated colts –Testes failed to grow during first 32 weeks –Irregular groups of Leydig cells –Reduced volume of semineferous tubules –Reducd Leydig cell volume *No P values given

10. The Second Study Twelve 2-year-old colts divided into two groups: 1) 200 mg dose 2) 400 mg dose of water based GnRH vaccine –They were run in paddocks and fed to maintain condition –Vaccinated against strangles and tetanus

11. The Second Study Injections: given Intramuscularly *Water based vaccine vs *Mineral Oil based vaccine Lesions Soreness Scarring

12. The Second Study Measurements and Tests Testosterone concentrations and semen quality assessed before trial Body Weights Testicular widths and lengths Blood samples Testosterone concentrations Antibody assays Semen examination Libido

13. Results Vaccination Dose on body weight and testicular dimensions –Not significantly different (P>0.05) Only slight swelling at site Vaccination dose on semen characteristics –Significantly different in percentage of live, normal sperm (P<0.05) No significant effects on antibody titres or testosterone levels –(P>0.05) Displayed gelding-like behavior Semen Characteristics 200mg400mg Live, Normal Sperm (%) 38.752.1 Sperm Concentration (10 6 /mL) 319.4294.0 Total # of Sperm (10 6 ) 47293893

14. The Third Study Four standardbred stallions: 3 treated and 1 control Vaccinated with water soluble GnRH vaccine –Kept in paddocks during day & stalls at night *September to January

15. The Third Study Measurements and Tests Hormone assays Semen collection & behavior Semen evaluation Testes examination Testicular histology Site examination

16. Results Testosterone levels decreased, but varied by individual Libido decreased # of mounts increased Time in collection room increased Interest in tease mare decreased No P values were given StallionTime Before Min:sec Week 13 A8:089:19 B2:5711:59 C1:086:50 D3:057:58

17. Conclusion Immunocastration IS an alternative to castration Needs more research May become the norm in the race and show horse industries DEFINITELY WORTH LOOKING INTO