Saturday, January 8, 2011

TJ Holmes Interview: How Did PZP-22 Affect the Mares?

(Above: the mare, Alpha--still nursing after 2+ years)

One of the questions I asked TJ, in the interview, was whether or not PZP-22, the vaccine given the horses she watches in the Spring Creek Basin, changes the behavior of the herds. This is a vital question because part of the guidelines the scientific community followed in developing a wild horse contraceptive included this: The vaccine should "not influence the social behavior of the horses."

Some, who do not endorse PZP say it does change the social behavior, so I was very interested in what TJ has observed in her herd.

Question: From your observations and knowledge, does PZP change the behaviors of wild horses?

Given that I'm observing a very small herd that has been gathered frequently in the last decade, I've found it hard to determine a baseline of normal behavior for my horses. Basically, I've decided to try to determine their behavior as "normal for them." The more I considered this question, the more complex the answer seems to be.

(The mare, Alpha)

In 2008, I observed Alpha being bred in different months - by the band stallion and by a young stallion I've always assumed was his son. This year, the band fractured socially, but they're still together physically (except for four youngsters and a few bachelors). All three mares have a single stallion, including Alpha. Five mares were given the PZP-22 and released after the 2007 roundup (all the released mares were given the PZP-22).

These are the mares that got the PZP-22:

Slate (1) died that winter.

Molly (2) died last fall (fall 2009) but had foals in both 2008 and in 2009, right on her established schedule - early June then late May.

Kiowa (3) was released with her foal, Reya, now 3, and I don't know when Reya was born. Kiowa's daughter Spook was born May 1, 2008; son Milagro was born July 1, 2009; son Maiku was born June 28, 2010.

(Kiowa and Maiku)

Chipeta (4) likely had not had a foal before the 2007 roundup; she did not foal in 2008 (neither PZP nor PZP-22 affects the fetus) - she is young ... although it's possible she aborted because of the roundup. Her first (I think) foal, Joven, was born July 26, 2009. He died at about two weeks - cause unknown. Her second foal, Puzzle, was born Sept. 1, 2010. Now why that delay?

(Chipeta and Puzzle--she had a foal die in '09)

Alpha (5) had Storm on July 25, 2008 - not affected by PZP-22.

Why so late?

(Alpha with Storm Winter '10/'11)

Alpha is an older mare, but I don't know her exact age. Did she have trouble conceiving? It was her I observed being bred by at least two different stallions. She has not had a foal since Storm in 2008. Again, age ... or atypical long-term effects of PZP-22? I don't know. Storm was still nursing as recently as last month - at 2+ years old (I'm not sure whether it's habit, comfort or whether he's actually getting anything, though Alpha's udder does seem fuller than it would be if she wasn't producing milk). Alpha is very healthy and in excellent condition, and Storm is as big and stout a wild 2-year-old as I've ever seen - so not only is the mare healthy and thriving, so is her colt.

The three mares from Sand Wash Basin received PZP-22 during their roundup, before they were trailered to Spring Creek Basin: They stayed together, by themselves, from the time they were released in late October until December that year, when I found them with Kreacher, previous low man on the bachelor totem pole.


(Kootenai, Raven, Mona and Kreacher--Corona is between Kootenai and Raven)

In spring 2009, Raven, who apparently went off to have her foal (obviously sired by a Sand Wash Basin stallion) was picked up by Duke, and the three of them spent several months together.


Duke later lost them back to Kreacher, and they're still with him. Mona ended up with Seven in September after she had her filly, Shane.

(Mona & Shane)

I want to address the "rape" allegation. The only stallion I've ever seen "chase" a mare - two - until he bred them was Seven, completely unrelated to fertility control - one mare (Molly) was bred by him on her foaling heat (about a week after she had Liberty), and the other (Roja) has never been treated with fertility control - I observed him chasing and mounting Roja two full months after she had her foal this year. I want to make this perfectly clear: RAPE IS ABOUT DOMINATION, not sex, not procreation, and it is PURELY a human construct.

I have NOT observed the frequent movement of horses between bands like I've seen and heard about in some other herds. I don't know why this is. Basically, I have not seen any massive, dynamic-altering behaviors among the horses treated with PZP-22 in Spring Creek Basin, certainly not enough to alter my feeling that PZP is the humane alternative to roundups and removals. While there are many guidelines of mustang behavior, the horses are individuals, and their behavior varies.

You can follow along with these horses as TJ documents them day to day, year to year--sunshine and snow. Spring Creek Blog

If you have any questions for TJ, please leave them in the comments. I'll start off.

Hi TJ--It appears, from your information, that the PZP-22 wasn't very effective in controlling reproduction. Do you have some thoughts about why it wasn't?


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  2. Another question, were the Sand Wash Basin mares released fall '08, and if so, is the PZP-22 more affective with them?

    And, it appears, if Raven was bred before she changed herds, the PZP-22 must not have affected the fetus.

  3. From TJ

    The PZP-22 given to our mares in August 2007 appeared to have been ineffective with the lone exception of Alpha (we'll never know how it may have worked on Slate because she died that winter). I had some private suspicions about that, and I have since learned that timing is VERY critical with PZP-22, as a time-release pellet that works with a mare's seasonally-regulated immune system (and I may not be saying that entirely correctly). August is apparently among the time range of greater INeffectiveness/lower effectiveness.

    Among the Sand Wash Basin mares (rounded up and brought immediately to Spring Creek Basin in mid-October 2008), Raven's 2009 foal (Corona) was obviously not affected by the vaccine. And I want to reiterate: Neither PZP nor PZP-22 affects a fetus a mare may be carrying at time of adminstration. PZP is a protein that simply DISRUPTS THE CYCLE OF FERTILIZATION. A HSUS documenter of the Sand Wash Basin herd had viewed and photographed Raven with Corona's band before the roundup and sent me photos; Raven's filly, which I named Corona, is most likely his daughter. This might also be "confirmed" by the amazing similarities of her likely half-siblings currently with his band.

    Raven did not have a foal in 2010. She should resume having a foal this year. She does look pregnant.

    Mona had a foal in September 2010. Given that they've realized that the 22-month efficacy hoped for with PZP-22 is really NOT 22 months, that's probably not bad.

    Kootenai has not had a foal, and she does not look pregnant ... but as I've seen with young, first-time pregnant mares, they don't always show off.

    The efficacy rate among the Sand Wash Basin mares (IN SWB) appears to be low, but I have only personal contact reports about that, not related to the actual study.

    The other herd in the Annenberg Foundation funded HSUS study (I should have clarified the study), Cedar Mountains, in Utah, was rounded up in December 2008, and PZP-22 was administered to the released mares. All I've heard about that study is that it has been more effective than the vaccine administered in October in Colorado.

    The timing matter has to do with biological reactions that I am really not qualified to describe.

    Another benefit of PZP over PZP-22 is that it can be done on the mares' biological timetable and is not limited to that of humans(roundups).
    (Although this can be and has been delayed by legal action in some cases.)

  4. I found it very interesting that Storm is still nursing at 2 + years, and I'm thinking, it's probably because Alpha has not conceived again--for whatever reason--PZP22 effectiveness or age. Which leads me to think that it is healthy to keep mares from breeding between foals--healthy for the mares and the foals, who get extra time on their mothers.

  5. I agree! I had never seen it before ... because domestic mares I've known had their foals weaned, and the wild mares wean their own. I'm watching now for signs - it's starting, but the mares still give in, by and large that I've seen. But yes, Alpha is very healthy (and so are Jif and Mahogany and Alegre who lost their foals last spring), and so is Storm, her colt. Think about grizzlies, whose cubs stay with them about three years. More time with mom, more time spent learning the ways of the wild. One very important thing they've seen with the Assateague mares is that they're living (much) longer - because they're healthier, not having foals year after year. Corona also nursed quite awhile. I haven't seen her doing it recently, and I've noticed Raven seems to be pregnant, so she has likely weaned Corona.

  6. TJ,in the beginning of this post, you report that a couple of mares died, as well as a couple of foals. Was the PZP-22 in any way responsible for these deaths, causing some sort of physical change that may have contributed to the horses' deaths? Even if it came from the stress or any injuries incurred from the roundups leading to the administration of PZP-22?

  7. Joanne - (I'm going to do this in parts ... it doesn't like my wordiness again, I think!) I should have been more clear about the timing of the mares' and foals' deaths, but no, PZP-22 did not cause the deaths. PZP stands for porcine zona pellucida. "Zona pellucida is a glycoprotein. This means it is a noncellular substance made from proteins combined with carbohydrates. It is a membrane surrounding the egg that acts as a barrier that interacts with sperm on a molecular level in order to permit or deny the sperm access to the egg." (See links below.) It simply blocks fertilization, and about as far down the process as you can get. It does not harm a fetus a mare may be carrying, and it does not affect the mare's health (if anything, having fewer foals because of fertility control actually makes the mares healthier, which, in turn, leads to healthier foals!).

    Slate died in the winter after the roundup, likely from some kind of catastrophic event (broken leg ...???). And I doubt it had anything to do with the roundup; the last time I saw her, and in the months between the roundup and the last itme I saw her, she seemed perfectly healthy. She would have been 9 that spring.

    Molly, who was aged at "older than 20" at the 2007 roundup, had two foals (2008 and 2009) before she died in the fall of 2009. Her 2008 filly died at about 2 months. The last time I saw her band with her in it, they were being chased by a man in a truck. It's pure speculation to say he caused her death, and yet I will never forget that - or him.

  8. Two other mares also have died - one in foalbirth that could have been prevented if she had been given PZP (my belief; and annual fertility control was not approved in the basin, so that's a moot point) and another older mare that also had a foal the year of her death; and including that foal, six foals have died since I started documenting in 2007 (I don't know the causes of any but the one Bones just couldn't deliver), from within a week of birth to two months. What's normal? It does seem that the more foals we have, the higher the mortality. A trainer I had once told me something along the lines of this: "People think that if you ride all the time, your chances of getting bucked off are fewer because you're more experienced. In truth, the opposite is true. The more times you ride, the more chances you have of getting bucked off!" I think that "law of probability" follows with foal births.

  9. "To summarize, PZP is simply a glycoprotein that surrounds the eggs of pigs. When used as a vaccine, it leads to an immune response that can eventually result in the prevention of fertilization. This is why PZP is referred to as an immunocontraceptive; it is a vaccine that works with the immune system in preventing pregnancy. It is not a hormone; and it does not act against any hormones, including those that are involved in reproduction. It again prevents pregnancy at the last possible step before conception, which is fertilization." (See links below.)

    There are decades of research behind PZP. It has been used on Assateague Island for 24 years (as well as other NPS-managed herds, the managers of which figured out early on that if they could slow the reproduction side, they could slow (or stop) costly and inhumane roundups and removals). PZP is safe.

    Please follow this link to the best series of PZP I've found (and it's illustrated). I refer to it constantly because it's so straight-forward and easy to understand. The quotes above come directly from this series:

    Specifically, on the reproduction-cycle topic, look at these links:


Please feel welcome to join our discussion by telling us about your own thoughts and experiences.