Spayvac Trials Best On Mares, compared to GonaCon and IUD

from "Cattlemen's Update" 2007 - pages 48-63
by Gary Killian

In the fall of 2002 and the spring of 2003 we initiated a study to compare the long-term efficacy of a single-shot contraceptive vaccine directed at gonadotropin releasing hormone (GonaCon) with that of a single-shot vaccine directed at the zona pellucida (SpayVac) with the use of intrauterine contraceptive devices (IUD).
The Nevada Department of Agriculture provided the feral mares which were maintained at the Nevada State Penitentiary, Carson City facility. Doses of the SpayVac PZP vaccine were kindly provided by the vaccine’s developer, Dr. Robert Brown. Contraceptive vaccines were given intramuscularly in the left lateral neck, administered with AdjuVac.

Multiyear contraceptive efficacy was greatest for SpayVac, followed by GonaCon and the IUD.

All mares in the SpayVac group were infertile ... during the first breeding season. In years two and three, 80% of the SpayVac-treated mares ... were infertile. It is noteworthy that the drop in contraception rate was greatest between years one and two with only minimal decrease from year two to year three. This suggests that considering the immunological response, there are two sub-populations of mares. One population responded with antibody titers adequate for contraception that were maintained over several years, versus the other population that lasted no more than one year.

The average titer for SpayVac contracepted mares progressively declined during each year of study. However, the average titer in year 3 for contracepted SpayVac mares was still nearly 8-fold greater than the average “breakthrough” titer for all SpayVac-treated mares that became pregnant. There was a 37% decline in titer between year 1 and 2 and a 33% decline between years 2 and 3. If we assume an average annual rate of decline in titer of 35%, this suggests that on average, the majority of SpayVac-treated mares will remain contracepted for four additional years before the breakthrough titer is reached. This projection of a total of 7 years of contraception for SpayVac-treated mares is supported by the literature report of long-term efficacy of SpayVac use in Grey seals (Brown et al., 1997).

This post has been edited by Faunak8 on Mar 16 2007, 10:49 AM

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Percentage of reproductive tracts with edema revealed by ultrasonography of mares for each of the treatments compared to the predicted number of mares expected to be in estrus:
Year 1 Predicted: 25%, GonCon: 23%, SpayVac: 82%
Year 2 Predicted: 25%, GonCon: 25%, SpayVac: 91%
Year 3 Predicted: 25%, GonCon: 25%, SpayVac: 100%

(All mares with SpayVac were found to be in estrus when checked in year 3, not that they checked the way we would ;)

The ZP vaccine doesn't effect the mare's cycle, it just prevents fertility. The GnRH vaccine would cause the cycles to cease. IUD's are useless in mares :)

There is a lot of money involved with finding a REVERSABLE, long term drug that prevents fertility but doesn't alter behavior (still shows heat). ZP vaccine seems to be the most promising, but all drugs have serious long term effects on young mares. They aren't at the point yet where you could vaccinate your own mare and turn her loose with a stallion.

The trial indicates you could for the first year (100% contraception), and a 1 in 5 chance they'd get pregnant the second year, though a booster every year would eliminate that chance.

More info on PZP here: http://www.beastforum.com/index.php?showto...l+contraception

The advantage SpayVac seems to have over other PZP vaccines is that it's much longer lasting due to encapsulation in liposomes (cholesterol and lecithin), this development being significant enough that it has been patented for use as a delivery platform for other vaccines, under the name VacciMax.

Its not 100%, I don't know where the OP found the article but other research shows different, less effective data.

The reason I said its not ready to vaccinate your own mare is a) you'd have a really hard time buying it because it doesn't hide estrus (the normal reason a horse owner would want the vaccine) and b ) it can cause PERMINENT infertility, which can be a major problem in some cases. The vaccine isn't ready yet, still in research phases :)

This post has been edited by Deacon on Mar 16 2007, 11:57 PM

The purpose of the study was to find the "most permanent" option, not a reversible one. Since it isn't targeted at cases of wanting it to be reversible/hiding estrus then it is ready for its purpose: an alternative to mass shootings of overpopulated wild non-indigenous animals which happen all around the world.

The OP isn't allowed to post links until reaching 100 posts, but googling for parts of the text should show it.

Feel free to cite the more recent research showing this. The purpose of research is to check improvements and chart progress to the point of being ready, which this and the following article (on deer) are showing:

from "Status of Present Day Infertility Technology"
by DeNicola, Anthony; Lowell A. Miller, James P. Gionfriddo and Kathleen A. Fagerstone.
Northeast Association of Fish and Wildlife Agencies.

"We treated 20 does with SpayVac (zp-based vaccine) in March 2003, 33 does with GonaCon-KLH (GnRH-based vaccine) in February 2004, and 27 does with a modified SpayVac formulation in August 2004 in Princeton, NJ. We also administered GonaCon-KLH to 29 does in Madison, NJ (July 2005) and 15 does received GonaCon-Blue in Newark, DE (August 2005). After one year (2004), only one of 20 (5%) does gave birth after receiving SpayVac. None of the remaining 14 SpayVac-treated does gave birth the second year (2005), and 7 of the 13 (54%) remaining does gave birth the third year (2006). None (n = 16) of the does administered modified SpayVac reproduced in spring 2005. Three of 12 (25%) remaining does in this same treatment reproduced spring 2006."

Now you need to cite two more research articles showing less effective data :)

The point of the research funded by the USDA is to find a REVERSABLE vaccine for use in controlling wild herds. Like I said, their requirements were: reversable; non-behaviorally modifying; effective; non-invasive.

Do a search on PubMed, you will find lots of data. I've done a lot of research in this field. The vaccine has some perminent side effects which are very undesirable, one of which is complete infertility for life. Would be nice, to stop irresponcible breeding.

If complete infertility for life would be nice to stop irresponsible breeding, please explain in what context this is an undesirable side effect, in respect to pets not intended for breeding.

I did the search and found nothing published more recently than the above studies. Please helpfully present the more recently published data citing findings of the other "very undesirable" side effects specifically of SpayVac in detail, otherwise there seems no reason to scaremonger.

I did however find an article on VacciMax being effective in sustaining vaccines for long periods in other non-contraceptive trials, and a few articles on something reversible called Adjudin for male animals:

A male contraceptive targeting germ cell adhesion. November 2006
by Mruk DD, Wong CH, Silvestrini B, Cheng CY

Adjudin is specifically targeted to the testis by conjugating Adjudin to a recombinant follicle-stimulating hormone (FSH) mutant, which serves as its 'carrier'. Using this approach, infertility was induced in adult rats when 0.5 microg Adjudin per kg b.w. was administered intraperitoneally, which was similar to results when 50 mg per kg b.w. was given orally (which in a small subset of animals resulted in adverse effects such as liver inflammation and muscle atrophy). This represents a substantial increase in Adjudin's selectivity and efficacy as a male contraceptive.


A good researcher is one who is just as jubilant about being proven wrong by data as being proven right ;)

I would look forward to this as my boys would like to go back to being pastured with the girls.
The issue is the market.
PMU mare foals are straining the "pet companion" homes.
The new ecomony is that few people can afford to keep horses.
The show circuits are bloudline dependant and that leaves the buyers going to a select few stables.

I would give my eye teath for a way to get the boys running with the girls and getting laid with out the foal that can not be sold despite the registration papers.

I am watching this and so are the boys.

Rus