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Discussion on Chemical Castration

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Whidbey Island Rescue for Equines
Username: montanya

Post Number: 6
Registered: 11-2002
Posted on Tuesday, Sep 2, 2008 - 11:25 pm:   Edit PostPrint Post

I am curious to learn more about chemical castration. What long term effects does it have on the horse if any, opposed to surgical castration.
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Robert N. Oglesby DVM
Username: dro

Post Number: 21316
Registered: 1-1997
Posted on Wednesday, Sep 3, 2008 - 7:17 am:   Edit PostPrint Post

Hello WIRE,
I am not familiar with any regularly practised chemical castration techniques used in horses nor can I find research on the subject. However there is a fair amount of research into vaccination against fertility in stallions in Europe and the UK:

Anim Reprod Sci. 2005 Apr;86(3-4):247-59. Effects of GnRH immunization in sexually mature pony stallions.
Turkstra JA, van der Meer FJ, Knaap J, Rottier PJ, Teerds KJ, Colenbrander B, Meloen RH.
Pepscan Systems, Edelhertweg 15, 8219 PH Lelystad, The Netherlands.

Immunization against gonadotrophin releasing hormone (GnRH) was studied as an alternative for the commonly used surgical castration in stallions. Two GnRH vaccines comprising non-mineral oil adjuvants were evaluated for their potential to induce high antibody titers directed against GnRH and subsequent effects on reproductive characteristics. Twelve sexually mature male hemicastrated Shetland ponies were assigned to three groups. Group 1 and 2 were injected with 1mg peptide equivalent of G6k-GnRH-tandem-dimer conjugated to ovalbumin (OVA) in CoVaccine HT adjuvant (GnRH/CoVaccine) and in Carbopol (GnRH/Carbopol), respectively, and group 3 was injected with CoVaccine HT adjuvant without antigen (controls). After immunization no adverse effects were observed with respect to the injections sites or general health. Two weeks after the second vaccination antibody titers against GnRH increased rapidly in all animals of the GnRH/CoVaccine group, at the same time reducing serum testosterone levels maximally for the further duration of the experiment. In the GnRH/Carbopol group antibody responses and effects on testosterone levels were intermediate in two stallions and not apparent in the remaining stallions of this group. Semen evaluation showed that from 2 weeks after the second immunization onwards, sperm motility was affected in all stallions treated with GnRH/CoVaccine and one stallion treated with GnRH/Carbopol. Seven weeks after the second immunization, no semen could be collected from two stallions, one of each group, due to suppressed libido. Histological examination of the testes, 15 weeks after the initial immunization, demonstrated reduction in seminiferous tubuli diameters in all stallions of the GnRH/CoVaccine group and one stallion of the GnRH/Carbopol group. Furthermore, spermatogenesis was extremely disorganized in these stallions, as indicated by absence of the lumen in the seminiferous tubules, the absence of spermatozoa and spermatids in the tubular cross-sections and the impossibility to determine the stage of the tubular cross-sections. Testis size was also substantially reduced in three out of four stallions treated with GnRH/CoVaccine. The results demonstrate that two immunizations with G6k-GnRH-tandem-dimer-OVA conjugate in a suitable adjuvant such as CoVaccine HT caused a rapid and complete reduction of serum testosterone levels in sexually mature stallions, subsequently leading to reduced sperm motility and affected testis function, while no adverse reactions were observed after immunizations.
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Username: maggienm

Post Number: 744
Registered: 6-2004
Posted on Wednesday, Sep 3, 2008 - 9:44 am:   Edit PostPrint Post

Very interesting. Do you know if the injections have to be continued annually? Are the effects permanent?
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Robert N. Oglesby DVM
Username: dro

Post Number: 21319
Registered: 1-1997
Posted on Thursday, Sep 4, 2008 - 7:39 am:   Edit PostPrint Post

No Lori, I have not seen any long term studies.
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