PZP, Castration and Horse/Human Relationships

Members of "The Tribe" frolic on a snowy day in February at the Ravenseyrie Sorraia Mustang Preserve

In one brisk movement Dr. Lazier took the severed testicle and flung it well away from where Interessado lay groaning. I quickly ran over to recover it from the mud and did the same when the second gonad made a similar journey. I set these aside for a proper, more respectful disposal. Soon Dr. Lazier and Kevin were helping Interessado remain steady on his feet. It was over. I had my first witness of field castration surgery and found it is not something for the faint of heart!

We had one more colt to do. The raw November day was quick to grow dim as we waited for the sedative injection to take effect on Silvestre so he would allow Dr. Lazier to inject him with the anesthetic. It did not. Silvestre's surgery was cancelled and rescheduled for the next day.

Interessado (3 yrs. old) gets drowsy from the initial sedative, administered by Kevin via a dart pistol.

The following day was just as cold and dim as the day before, and once again mild-mannered Silvestre did not respond to the drugs in the typical manner most horses do.  It took a triple dose of both drugs (Xylazine and Ketamine) to bring the two year old Sorraia Mustang down and even that proved insufficient as he violently erupted to his feet just after the first testicle was emasculated. Dr. Lazier injected more anesthesia and somehow amidst frigid winds, icy mud and an equine mind twisted by synthetic chemicals the surgery was completed.

I had placed Silvestre's testes atop the nearby manure heap to retrieve when all was finished. While still heavily compromised by the effects of the drugs, Silvestre stumbled and staggered his way over to the eight foot mound and tried to climb it, which was a strange and unsettling end to his life as a young stallion.

Silvestre (2 years old), the day after his castration surgery...in pain and depressed

Then there were weeks of monitoring leaking fluids and swollen sheaths. My vet did not tell me about the potential for dreadful and dire complications. Aren't we all under the impression castration of horses is a simple, routine procedure that does not impact the animal all that much (with the exception of ending his ability to reproduce and altering his behaviour)?

The beach at Ravenseyrie:  the perfect setting to contemplate weighty decisions involving the equines who live here.


The reality is that 20% of equine castrations result in one or more complications that impede healing--or worse, claim the life of the horse. This form of equine contraceptive has been routine for thousands of years and even during modern times, with the application of sedatives, tranquilizers, anesthetics, etc., it is not benign--not one bit.

For us, it was the first time we had deliberately caused these horses harm. They were healthy, robust young lads and we purposefully had them wounded and put them in a potentially life threatening situation. It gave us pause... These castrations became for us just one more unpleasant aspect of participating in and managing a preserve for a type of endangered wild equine where breeding is allowed to take place.

Full brothers:  Interessado and Silvestre, healed and in good form after being gelded in November of 2011

In the six years that Kevin and I have devoted our lives to saving the Sorraia, we have experienced unparalleled joys. Making it possible for these inspirational equines to live a mostly autonomous existence has further altered our philosophical views on horse/human relations as we observe and participate in their rich, interesting culture. We find ourselves now, more than ever before, reluctant to introduce leather straps of control over these beings. We find the process of selling (donating wouldn't make it any different for us) the offspring riddled with unpleasant tasks to ready them for a life elsewhere and rife with sentimental hardships. Never having experienced this before, we could not forsee how changed we would become and how unfit it now makes us for managing a breeding preserve.

 Altamiro

These same elements that have convinced us we are not, after all, the type of individuals who should be breeding and selling horses also has us unwilling to end it by dispersing the herd, or separating Altamiro from his mares by forcing them apart with fencing. Gelding Altamiro would, in one swift action, settle the matter...But you do not castrate the only purebred Sorraia stallion in Canada. (Who also is one of just two purebred Sorraia stallions in all of North America.) Another form of equine contraception was sought and after researching the options as thoroughly as possible, we found oursleves--once again--determining PZP to be the most effective, least invasive, lowest risk alternative to castration or separation.  Its use on wild horses has been closely monitored by scientists for over twenty-two years and last month PZP received its official registration status by the Environmental Protection Agency through the sponsorship of the Humane Society of the United States.

Altamiro with his son, Interessado the day after Interessado was castrated

Not everyone agrees. of course, that the PZP equine contaceptive is the appropriate choice, and two breeders involved with the Sorraia preservation have asked how Kevin and I could make this decision--since it is definite manipulation of the herd and not completely free of risks. Specifically, these concerns have been raised:

--In some studies it has disrupted herd dynamics and grazing habits

--It has the potential to induce auto-immune disease

--It can render the mares permanently infertile

--Stallions will be stressed by the continual breeding and defending of mares in heat

Levada

Tocara

These concerns are addressed in a question and answer document titled:

Immunocontraceptive Reproductive ControlUtilizing Porcine Zona Pellucida (PZP)in Federal Wild Horse Populations

 (Double click the above title to read the document.)

At the end of the document is a bibliography of research articles (nine pages long!) which are helpful if one wants to read further about any of the issues concerning PZP.   After reading the Q&A and accessing many of the articles referenced, Kevin and I overcame our reservations, realizing that the potential risks are miniscule when compared to the detrimental elements inherent in castration as well as other contraceptives in current use on either stallions or mares.  To my way of thinking, PZP's potential for harm to the mares is far less than the potential harm caused by traditional stabling, equestrian sports, artificial insemination and pregnancy itself.

Unless humans are willing to take down the fences in wilderness areas and let horses live their lives apart from us, we will in one form or another be impacting their natural proclivities and find ourselves faced with making decisions that alter their way of being.  Each of us who love and live with horses seek the decisions based on our individual situations.  What we have decided to do here at Ravenseyrie might not be the answer for someone else in a similar situation.  We may find in the future it wasn't right for us either...but we had to make a choice--our land and finances are limited, and we have, as mentioned before, a certain philosophy of horse/human relationships that underscores these decisions profoundly.

Silvestre receives a rebuff rather than a welcome from Levada during his first attempts to reintegrate with the non-breeding group, a collective of Altamiro's offspring we refer to as The Tribe.

Additional Information:

On April 12th, I received an email from Dr. Jay Kirkpatrick, the developer of the PZP immunocontraceptive vaccine, which I reproduce here with his permission to further dispel the real and the imagined apprehension regarding potential risks of using this vaccine as fertility control among wild horses: 

Dear Ms. Gerard,

Kim recently passed your blog on to me and I found it encouraging and fascinating.  I applaud your efforts and we are delighted to be able to help you. 

As I read through the journal I came upon the section that listed the concerns/risks associated with the use of PZP in horses, and I thought I might add to what you already know.  I do this to help you educate those who still have concerns.


--In some studies it has disrupted herd dynamics and grazing habits

The studies most recently cited as "disrupting" herd dynamics have all come from Cape Lookout National Seashore horses (Shakleford Banks).  What the studies do not tell you is that the "controls" are a group of nine mares that are never treated and which get pregnant on a regular basis and then have their foals taken from them.  These mares, as a result of their constant state of pregnancy and loss of offspring, are not in as good condition as those treated and without foals.  One could conclude from this study that mares not treated and permitted to get pregnant on a regular basis and then have their young taken from them tend to stay within their band more often than those who get treated and do move more frequently.  The point is, that these studies have not used legitimate controls.  In contrast, 24 years of management of the Assateague Island horses with PZP has not resulted in any difference in movement between bands by treated or non-treated mares.  The primary difference between these Assateague mares and the Cape Lookout mares is that the former are not chased allover the island with ATVs and then have their foals forcibly removed.  Nor was the Cape Lookout study controlled for age of band stallion, which is the single largest determiner of mare band fidelity (the older the stallion, the more fidelity).  There are several other factors that are associated with the fidelity of mares to the band and none of these were controlled for in that study.  But, no one would know this reading the paper.

There has been a study with western wild horses that shows that the time budgets of treated horses was different from those of untreated horses.  But, the conclusions were that it was the better body condition of the treated mares (as a result of removing the physiological stress of lactation), and the absence of foals, and the significantly greater longevity in treated mares that led to the changes in time budgets.  We need to ask if a human with poor health and condition spends their time the same as one in good condition, or whether a human with a baby spends their time in the same manner as one without a baby, or whether older people spend their time in the same manner as younger folks.  In other words, differences in time budgets simply reflect the results of successful contraception.

In no case, over 24 years of PZP use on wild horses has anyone ever demonstrated that harems fell apart, or that bachelor groups did not form, or that mare hierarchy changed or that any of the fundamental evolutionary-driven social structure/behaviors have changed.

--It has the potential to induce auto-immune disease

Perhaps that potential is there, but 24 years of use on horses has not resulted in this.  The literature, as you point out in your blog, reflects the following changes:  better body condition, decreased foal mortality, significantly greater longevity.  Autoimmune disease would not be associated with better health! 

--It can render the mares permanently infertile

We first published extensive reversibility data in 2002.  Basically it showed that a mare treated for three consecutive years would reverse in a mean time of about 4 years.  However, the range is 1-9. Thus, some mares will take much longer than others, and some will reverse really fast.  That is no different than humans and flu vaccine.  We are at the mercy of the target animal's immune system regardless of the vaccine.  Some will turn out to be poor responders and not become infertile at all - fortunately very few.  Some will respond very strongly and take much longer to return to fertility, and there is the possibility that a very small number - only a few - out of hundreds and hundreds - might never return to fertility.  Fortunately there is a norm for immune responses and most mares will fall within that norm.  We do have data that shows that mares treated for seven consecutive years probably will not reverse, but if you are treating a mare for that long, you probably don't want her to breed again anyway.  This all brings to focus the importance of your management plan.  Any contraceptive is no better than the plan under which it is put to work.  Much of this concern comes from quarters who focus only on the exception rather than the general.

--Stallions will be stressed by the continual breeding and defending of mares in heat

This is categorically false and there is no data whatsoever to support it.  First, horses are seasonal breeders and they seldom cycle (with ovulation) outside the seasonal breeding season, whether they are treated or not.  Second, the further north the herd, the more sharply defined the breeding season - and you are north!  Third, mares have what we refer to as transitional seasons - in the fall and spring.  That is, they start to ripen a wave of follicles (eggs) and the production of estrogens are associated with this phenomenon.  This causes estrous behavior, but ovulation does not occur.  So, often we see mares demonstrating estrous behavior outside of the breeding season, but this is not an ovulatory cycle and it occurs in non-treated mares - in the spring and in the  fall.  Once again, over 24 years we have not had any stallions fall over, or get thin, or wear themselves out.  The point here, is that there is not a single piece of data to support this idea.  It is someone's "concern" based on pure speculation.  We have gone through the same thing with deer and PZP and perception.  IN deer PZP actually does extend the breeding season (unlike horses) but there are no deleterious effect on bucks. 

Well, these are just a few thoughts, intended to help you.  Keep up the good work.

Jay

Jay F. Kirkpatrick, Ph.D.
Director
The Science and Conservation Center
2100 S. Shiloh Road
Billings, MT  59106
(406) 652-9718

I'd also like to take this opportunity to direct readers to the website of the Science and Conservation Center, specifically to their page embedded with educative videos--the lower video is especially illuminating and I highly recommend you take the time to view it.

In my response to Dr. Kirkpatrick, I wrote: "I tend to be mostly reserved toward science, especially when it too frequently becomes the benchmark of "reality" at the expense of other means of perceiving, measuring and understanding the world in which we live.  But I do recognize there are times when laboratory creations provide something truly helpful in specific situations where our human impact has created an imbalance in nature and we are unwilling, or unable, to withdraw and let nature right things without our manipulation."

I look upon this minimally invasive approach to fertility control Dr. Kirkpatrick has developed to be helpful in situations like our Ravenseyrie preserve and other instances where humans coexist with wildlife and stability of numbers is essential to the holistic health of the environment and all its inhabitants.  It would be a travesty, however, if there were in the future no truly wild places left where horses can live out their lives without human intervention of any kind, as they presently do on Sable Island, here in Canada.  I hope that other regions in the world, where wild horses and human interests are volatile issues, will follow a similar program and allow some wild horse ranges to be equally protected and completely free of human manipulation.

The family band on the Ravenseyrie Sorraia Mustang Preserve in the spring of 2011

Let's get back now to the Ravenseyrie Sorraia Mustang Preserve and issues specific to our situation...

After four years of delivering high quality offspring, of each of our mares has made a significant contribution to the genetic pool of the endangered Sorraia horses, whether this is fully appreciated by the world at large or not. We are looking forward to foals this year from Bella, Belina and Zoriata and if they never have another pregnancy, it is no longer a vital thing--they have left their mark and fully embraced their experiences. Bella, Belina and Zorita (as well as Ciente, who died last year) have always meant more to us than strictly being broodmares anyhow. They can continue to live in virtual freedom in the presence of their stallion and whichever of their offspring destiny shows us need to remain at Ravenseyrie.  The PZP is presently in cold storage and we expect to dose the mares next week.  

Zorita and Belina enjoying their late day hay on a winter's day earlier this month

With Altamiro remaining entire, we retain the option to breed him to an outside Sorraia or Sorraia Mustang mare in the future, if certain aspects fit his present way of life. Once the contraceptives take effect we will no longer be a breeding preserve for the Sorraias, we will nevertheless continue to be safeguarding their genetics and continuing our efforts to raise awareness about the irreplaceable value of these types of horses to the equine species and overall biosphere. Likewise, I will continue to write about the lives of these magnificent horses with whom we share our lives here on Manitoulin Island.

Interessado and Altamiro

While it is a one of my favourite things to develop a relationship with each of the horses who have been born here, it has been painful to find that friendship ending when they leave Ravenseyrie and embark on new futures elsewhere.  Likewise, the time and work involved with an ever increasing number of horses makes deepening the relationships I have all the more difficult.  Both Kevin and I will miss the annual arrival of foals and watching them grow (though PZP is 95% effective, leaving a 5% potential for a surprise now and then), but we look forward to the new opportunities that will manifest themselves once the herd size is stabilized and we no longer have to make decisions about selling, castrating, separating, etc.  I am sure there will be many interesting and inspiring stories to share and on a more frequent basis than time has allowed this past two years.

Update 01April12:

 On Monday, March 26, Bella, Zorita, Belina, Fada and Pinoteia each received their primer dose of the PZP immunocontraceptive and will receive the follow up dose in three weeks.

In the journal entry titled, Gosto Gusto which announced the arrival of our first foal for 2012 Diane Pinney left a comment which more appropriately belongs in this journal entry discussing fertility control, so I have copied and pasted her comment here as well.

"Lynne, words cannot express how saddenned I am by your apparent closing the book on your Sorraia Mustang breeding program there, and no longer being an active participant in a valuable genetic conservation project. You appear to have decided that once you give all your mares the PZP, which I have never supported in any horse herd, that is the end of the story and the horses will only be providing you a visual reward. I would much rather have heard that you were trying to lease out the majority of mares to Sorraia Mustang preservationists, and only keeping one or two so that Altamiro has his own mares still, even if you PZP'd those. If that is something you tried, then I did not get that request to see if I were interested or knew anyone who might have been. Seeing a program that I thought was firmly dedicated to the Sorraia Mustang program being terminated in this way just breaks my heart. I hope that some day you change your mind."

---Posted by Diane at Spanish Sage Ranch to Journal of Ravenseyrie at March 31, 2012 12:10 PM


Diane, I am sorry that the choices Kevin and I have made and the reasons we have shared which led us to the decision to place our mares in the PZP immunocontraceptive program have caused you to feel so distraught.  Let's try and look at the positive elements and see if we cannot give you something to feel good about when you contemplate the shift in our mandate here at the Ravenseyrie Sorraia Mustang Preserve.

Each and every filly and colt that has been sired by Altamiro and born to our mares we have offered up for sale for others who are interested in the preservation of the Sorraia and Sorraia Mustang horses.  Two breeders have taken advantage of these offerings by selecting and purchasing offspring for export to their own preserves. 

Pinoteia, Esperanda and Altavida are three terrific Sorraia x Sorraia Mustang fillies that are still available and each of them surpass their dams in overall Sorraia characteristics.  There remains also the stellar stud prospect of Legado available for preservation minded breeders.  No doubt Bella's 2012 colt, Gosto will also be an exceptional stud prospect and we are still expecting foals from Zorita and Belina for this year, after which the fertility control should mean no foals for 2013.  So you see--we have yet a great offering of these rare genetics for other preservationists to get their hands on, one only has to contact us to begin discussions for purchase!

Leasing is not an option for us* as we do not see these horses as chess pieces to be placed in strategic places, though we can appreciate that from a strict preservationist perspective this is what would be preferred--it isn't something we personally desire to engage in.  Also one must consider that these horses are presently living on a remote island in Canada and anyone who would contemplate a lease would find themselves taking on an expensive undertaking for a simple lease.  Negotiating a purchase, dedicating oneself to these horses long-term and being able to provide them an appropriate habitat (whether five acres or five hundred) that is stable and secure are things we feel are essential.

*With the exception of a possible lease to a secondary preserve here on the island should such an opportunity present itself.

As for our foundation mares--our pact with them has always been that they remain here.  They each have provided a greater contribution to the overall genetics through their offspring from the past five years and we do no disservice to the preservation efforts by placing them on fertility control, which is reversible in most instances.  Those fillies who have not yet been selected for export by new owners will be placed on the immunocontraceptives once they come of age sexually, yet will remain available for purchase with the same considerations for their welfare as before. 

Ravenseyrie has proven that the Sorraia isn't a manmade "breed", but is a primitive "type" whose genetics can be easily consolidated by bringing together a European Sorraia with select mustangs of Sorraia type, thereby helping to alleviate the present bottleneck the Sorraias in Germany and Portugal are experiencing.  One can appreciate the great value these Ravenseyrie offspring have for continuing the conservation of the Sorraia and Sorraia Mustang genetics.  Our contribution carries on like ripples in a pond and ought to inspire other conservation-minded parties to initiate their own preserves.  One can follow the template we have (pairing a European Sorraia with Sorraia Mustangs) or utilizing only North American mustangs of Sorraia type.  Either option will be exponentially advanced by incorporating the available Ravenseyrie offspring--and that, Diane, I hope, is what you will focus on to alleviate your broken heart.