The Mustang Management Contraceptive Primer

MUSTANG MANAGEMENT CONTRACEPTIVE PRIMER 

This is not a debate on which is the best method of controlling wild horse numbers. These are simply the facts. It is clear science is far from perfect but research and observation can serve to give us an idea, a general sense of something which can compel us to look for more answers and continue research, preferably as humanely and as compassionately as possible. This is also not a debate as to whether mustangs should be classified as a native species in North America, returned native species, indigenous or invasive. They are here, with limited resources, and they are our responsibility.

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Porcine Zona Pellucida (PZP):  The compound PZP, which is short for Porcina Zona Pellucida, is derived from sow ovaries. When the pigs are slaughtered for the meat industry, the excess tissue not used for the food industry is either discarded or utilized for non-consumption purposes. Some tissue used for research and others for the preparation of drugs. Heparin is a potent anticoagulant given to almost every patient who has had surgery followed by an overnight stay in the hospital, to prevent the formation of blood clots. Heparin is derived from pig intestines. Insulin, given to diabetics, was originally made from cow, pig, and even whale pancreases. Currently there are still some available that contain animal products, although there are genetically modified human insulins and insulin analogs that are not animal based (http://iddt.org/about/gm-vs-animal-insulin).

Pesticide Classification: The FDA classifies PZP as a pesticide simply because they do not have a category for contraception. Pesticides control the numbers of a populations be it insect or mammal, and because they can be quite destructive, pesticides are deemed as negative chemical compounds. PZP does not have any direct effect on any of the plants or animals other than the inoculated mares.

How it works: PZP works by stimulating the immune system of a mare to produce antibodies which migrate through the horse’s body to an oocyte (egg). When the mare ovulates, the antibodies immediately surround the egg, making it impenetrable to sperm. The egg cannot be fertilized and there is no foal. The reproductive behavior remains relatively normal, the mare goes into estrus and is covered by a stallion but there is no resulting offspring (Barber, Lee, Steffens, Ard, & Fayrer-Hosken, 2001).

Risks: PZP is not without risks. The currently long acting PZP-22 can last approximately 22 months. PZP is based on the immune system of the mares and this can cause variation in the efficacy and duration of the contraceptive effect. As in humans utilizing long term injectable contraception (Depo-Provera), the mare’s return to fertility is quite variable (Kirkpatrick et al., 2009). The reason PZP is not offered to humans is because the efficacy rate is not high enough.

“For contraceptive treatment to be an effective management tool, it usually needs to be reversible (Kirkpatrick & Turner 1991). A long term study of feral horses showed that PZP was reversible even when females were treated for several years (Kirkpatrick & Turner 2002). However some females appeared not to return to full fertility after long-term PZP treatment and similar side effects were seen with GNRH treatments in deer (e.g. Miller et al. 2000a). Consequently, most wildlife contraceptives are reversible, or have minimal impact after prolonged use.”  (Gray & Cameron, 2010).

Prolonged use has demonstrated that some mares will never return to fertility. Kirkpatrick, Liu, Turner, Naugle, and Keiper (1992) found that three factors determine the return to normal reproductive function: the amount of PZP administered, the number of antibodies produced by the mare, and ovarian dysfunction. Earlier studies also demonstrated damage to ovaries although the PZP preparation was crude in the earlier stages of development (Kirkpatrick et al., 1992).

Abscesses at the injection sites have been reported but these are temporary, and heal without complications.

PZP and Tuberculosis: Finally, there were some rumours floating around social media that PZP can cause tuberculosis. Although this may sound like science-fiction or the nefarious work of people against keeping the horses wild, there is some truth. The original method of getting PZP into the animals involved piggy-backing the molecule on a carrier molecule or adjuvant. Adjuvants are not biologically active but their presence can trigger an immune response. It may result in a false positive antibody response for tuberculosis. The animal doesn’t have the disease, and many human vaccines work this way by stimulating the body to form antibodies to something not biologically active.  The original choice for the adjuvant was a mycobacterium- the mycobacteria family are known to cause tuberculosis and many other diseases. Because the PZP was attached to an inactive mycobacterium, in some animals it cause a false-positive tuberculosis antibody response. They changed the adjuvant for the preparation of PZP so now there is no mycobacterium involved. Additionally, horses cannot contract or transmit tuberculosis (Lyda, Hall, & Kirkpatrick, 2005).

GONACON: This method works by injecting mares with a synthetic (man-made) chemical compound called GonaCon. This compound acts against a hormone called gonadotropin releasing hormone (GnRH). In the reproductive cycle of mammals, GnRH is produced by the anterior pituitary gland. This gland controls reproduction by stimulating the release of the follicle stimulating hormone and the luteinizing hormone (and others). ConaCon works by stopping the production of GnRH and subsequently the luteinizing hormone and without LH, there is no ovulation, no corpus luteum, and therefore, no egg/offspring (Speroff & Fritz, 2012). Like PZP, GonaCon can result in prolonged infertility (Ransom, 2014). The tables below represent one study each- these data are only reflecting the results one study and may not have generalisability to the entire population. The general consensus amongst zoos and researchers is that PZP is 90% effective when administered correctly.

In a study by Jason I. Ransom et al. (2014), the researchers found there were fewer behavioural differences in mares treated with GonaCon, compared to those treated with PZP. They modeled their GonaCon study after the PZP study and found fewer alterations in the wild mare's behavior. GonaCon is still a recent addition to the world of wildlife contraception and has potential as a potential management tool for equids. It shows promise but the long-term data is still unavailable.  

GonaCon can be given to males because the GnRH stimulates testosterone production in males. However, studies of stags treated with GonaCon resulted in antler deformity and other negative consequences. "In conclusion, the GnRH vaccination in male rusa deer resulted in the increase in GnRH antibody titer, which negatively correlated with blood testosterone. The decrease in blood testosterone might be involved in the lower semen quality and poor antler development" (Phraluk, O. et al, 2015). There is potential for use in stallions but we need more research in this area.

Because GonaCon a works systemically, not targeting the reproductive tract as specifically as PZP, the potential for side effects increases. The closer to the intended target a medication or treatment is administered, the more effective, the lower the dose, and adverse drugs reaction are substantially decreased. The Global Library of Women's Health states: "In non-reproductive tissues, GnRH has been reported to modulate neuronal migration, visual processing, digestive tract function, and immune T cell chemotaxis. Studies in endometrial, ovarian, and prostate tumor cell lines have implicated GnRH in mediating cell growth, angiogenesis, invasion, and metastasis." (http://www.glowm.com/section_view/heading/Gonadotropin-releasing%2520Hormone%2520(GnRH)%2520and%2520the%2520GnRH%2520Receptor%2520(GnRHR)/item/284)

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Table 1. (Represents data from one study)

Infertility over three-years with equine contraception (Kilian et al., 2006).

	Infertility after one year	Infertility after two years	Infertility after three years
Spay- Vac PZP	100%	80%	80%
GonaCon	94%	60%	53%
Copper IUD	80%	29%*	14%*
*The assumption is the IUD’s had been expelled in the mare who became pregnant

Table 2. (Represents data from another study)

Foaling rates at three horse management areas after PZP treatment  (Ransom, J.,et al, 2011).

	Foaling Rates		Type of contraception
	Treated	Untreated
Little Book Cliffs	6.6%	60.1%	PZP in liquid form requires annual boosters
McCullough	31.7%	75%	PZP in pelleted form- designed to last two years
Pryor Mountain	17.7%	62.8%	PZP in liquid form requires annual boosters

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Any time we begin to tamper with Mother Nature- it places us at risk. Treating mares with immunocontraception and/or Gonacon can have negative consequences on the familial structures of a highly social animal. Treating mares with these two compounds can result in mare giving birth to foal during time of limited resources. A study determined that there are differences in parturition times for mare treated compared with mares that were not treated. Foals born during more normal times for wild horses have a higher survival rate. (J. I. Ransom, Hobbs, & Bruemmer, 2013).  

However, all negative consequences of injectable contraception pale in comparison to the disruption of the social structure during round-ups. Separation of mares from stallions and their offspring occurs during round-ups and culling. Family bands are broken up and the horses face the terrible loss of their freedom. A balance must be found and the benefits and the negative outcomes must be weighed. There is a chance a mare treated with the above methods, may never foal again- but that mare remains free. There is always the potential she may resume ovulation however, she is will not spend her life in a holding pen. A study by Turner, Liu, Flanagan, and Rutberg (2007) indicated one mare out of sixteen in the study, did not have a normal return to fertility. Is a chance of infertility worth the price of freedom?

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OVARECTOMY: This is removal of a mare’s ovaries. This method is irreversible, the mare will never breed again. Behaviorally, it reverts a mare to a non-breeding state. There is not a lot of data and/or research regarding this permanent method in the wild horse population which is why research proposals are being requested by government agencies The risks are the this surgical procedure are post-operative infection and possible abortion of a fetus if the mare is gravid at the time of the procedure.  Additionally there is the loss of that mare's potential contribution to the genetic diversity of that herd management area.  This loss is not well defined and may vary based of the genetic variation in a herd management area. Mares should be monitored for three weeks post-operative (optimally), before being returned to the range to live out their lives. The upfront cost is high, but the end result is permanent. It has been proposed for mare over a certain age, selected by the currently proposed studies, as means to control the populations which would allow the mares to live free without foaling year after year (Speroff & Fritz, 2012, National Research Council, 2013).

CHEMICAL STERILIZATION/VASECTOMY/NEUTERING:  These methods, performed on stallions, are permanent means of limiting wild horse populations. In chemical sterilization, stallions have a solution injected into the testes which causes necrosis and eventual tissue death of the testes. It is painful and carries a high risk of infection but is very cost-effective (Zhanwei, 1989),  Orchiectomy (removal of testes: aka gelding/neutering) is another permanent method which removes the testes of a stallion. Like chemical sterilization, ‘gelding’ causes behavioral changes and the stallions become less aggressive, there is less fighting and they cannot reproduce. Vasectomy involves severing the vas deferens of a stallion so that the communication between the testes and the penis is removed. The sperm are not able to be passed through the urethra during copulation. Behavior remains the same because the testes are still present and producing testosterone. Infection rates are much lower in vasectomies, the procedure is less painful but it requires a delicate touch, it may not be 100% effective, and the horse must be anesthetized or sedated (Speroff & Fritz, 2012, National Research Council, 2013).

ROUND-UPS: This method involves gathering the horses by use of helicopters, men on horses, ATV, trucks, and bait trapping. The bait-trapping is the least likely to cause physical harm but none of these methods are without significant risks. Helicopter round-ups have the highest incidences of morbidity and mortality.  The horses are gathered, separated and either returned to the horse management area, or they are removed to a holding facility for potential adoption.

RESERVE DESIGN:  This method of mustang management has merit in a perfect world. The theory is to find a place for the horses to live. A place that has natural horse-predators (may prove to be difficult to find), natural barriers to prevent migration in/out of the area, and neighbours sympathetic to mustangs.  The area has to have sufficient food, water, shelter, and other necessities for survival year round. Funds for this preserve may be obtained through ‘eco-tourism’ and public education regarding the wild horses are included in this plan.  Reserve design is a wonderful idea but it does not have practical application. The land that would be needed is not available, at least not at this time, for the numbers necessary.  The monitoring of these herds and the management of these herds must be carried out as well and the necessary people to oversee each area. The goal of 'reserve design' is to be self-sufficient in which the wild horses achieve homoeostasis with regards to population growth. Because the predation is very low, and we cannot safely import predators, this will prove to be challenging. Incorporating natural predators to assist in controlling the wild horse population can have deleterious effects on the domestic population of horses and of livestock. Historically, once a predator begins to hunt within the domestic population, the end result usually has rather negative consequences for the predator.

SELF-REGULATION: This involves leaving the mustangs alone to establish population equilibrium without any interference. There is no scientific evidence that this methods works and history has shown us wild horses do not fare well with a hands-off approach. Unfortunately the resources the mustangs have within the management areas are limited and the horses will suffer in one way or another if left unmanaged. There are three factors that determine a population’s ability to grow. They are: available resources, predation, and disease. Many of the wild horses at Cold Creek starved to death or had to be humanely euthanized because resources became compromised.  The resources may be limited due to naturally occurring factors such as drought or fire, or they may face competition from livestock grazing on the same land. Regardless of the mechanism, reduced resources will cause competition, and result starvation or disease in the wild horse population. Occasionally a mountain lion will take a foal or an older/injured horse but cougars are not primary predators of the mustangs . Wolves generally do not live in the horse management areas with any regularity. Disease is a concern with any animal left in overcrowded situations. Chronic Wasting Disease is a disease that began in the mule deer population, and has spread to other cervids (herbivorous even-toed mammals in which the male carries antlers). The current deer populations are substantially larger than the available resources in the north-east United States, and this disease has now been identified in white-tailed deer of the Adirondack Mountains. Similar to Bovine Spongiform Encephalopathy (BSE), or Mad Cow Disease, this disease is affecting all cervids, not just the deer (Chronic Wasting Disease Alliance, 2016).  If the populations of wild horses were left alone, they would increase to the point of starvation and disease. It would only be a matter of time before a disease mutated in that population and spread to the domestic horse population with devastating consequences.

DECLARING THE MUSTANG “ENDANGERED”: This method is to first declare the mustang a ‘native wild species’ and then have it declared endangered- which may prove difficult. The mustang is the same species as domestic horses. They fall within the same genera: Equus and species: caballus. They have no genetic markers or any other characteristic that differentiate them from their domestic counterparts.  There has been proposed theories that they behave differently but this was not enough for the United States Fish and Wildlife to declare mustangs as a separate subspecies.  The wild horses are identical genetically, physiologically, and behaviorally to the horses in your paddock.  There are currently 40-50,000 presumably wild horses in captivity at BLM holding facilities. There are an estimated 20-40,000 living wild on horse management areas, and several thousand more domesticated mustangs living with people. These numbers alone are not sufficient for endangered species status, or even threatened species if USFW was willing to grant them subspecies status. 

Proponents of making mustangs endangered believe that once they achieve the endangered species status, the mustangs would be granted the ultimate protection. However, advocacy groups would no longer have a say in their conservation; they would be managed by Fish and Wildlife. The now ‘endangered’ mustangs may be moved to locations to protect their numbers and they may very well lose their freedom if they were to ever to gain protected status. Our descendants would not be able to see these 'endangered mustangs' living free; they would only see them in zoos and protected reserves.

The belief that mustangs are a separate species or a separate animal from domestic horses is the first hurdle to overcome with this method. However, that has proven to be impossible. They are not separate; they are the same species just as a miniature horse and a Clydesdale are the same species. They are horses that have returned to the wild and been wildly successful at surviving and reproducing.   

“Managing them to extinction” is a catch-phrase often used to describe the situation of the wild horses. Mustangs will never become extinct because they aren't recognized as a separate sub-species of the modern horse. However, there is a very good chance our children and their descendants will never see a free roaming mustang, and that would be the greatest tragedy of all. Regardless of their origin, regardless of their heritage, the mustangs are our responsibility. We need science to save the mustangs, scientists with the necessary credentials and expertise in wildlife management, ecology, contraceptive experts, and equine ethology all working to establish the best and most humane method of managing wild horses. Each management area is unique and each management area needs its own method of achieving appropriate and healthy numbers. The phrase "managing them to eradication" is more accurate, less sensational rhetoric and implies the same message without any controversy regarding the species/subspecies status of the wild mustangs.  

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Meredith Hudes-Lowder is a Nurse Practitioner in Women’s Health and an expert on contraception. Additionally, she has a bachelor’s of biology with a concentration in environmental education.  She will graduate in May 2016 with a Doctorate of Nursing Practice. She runs the largest exclusively wild horse photography site on Facebook with Karen McLain- they have almost half a million fans. Bruce Lowder was consulted for this blog. He is a wildlife expert, naturalist, and worked for U.S. Fish and Game.

References:

Barber, M. R., Lee, S. M., Steffens, W. L., Ard, M., & Fayrer-Hosken, R. A. (2001). Immunolocalization of zona pellucida antigens in the ovarian follicle of dogs, cats, horses and elephants. Theriogenology, 55(8), 1705-1717. doi:10.1016/s0093-691x(01)00514-3

Gray, M. E., & Cameron, E. Z. (2010). Does contraceptive treatment in wildlife result in side effects? A review of quantitative and anecdotal evidence. Reproduction, 139(1), 45-55. doi:10.1530/rep-08-0456

Chronic Wasting Disease Alliance (2016). Webage URL http://www.cwd-info.org/index.php/fuseaction/about.main. Accessed 01/11/2016.

Killian, G., Diel, N., Miller, L., Rhyan, J, Thain, D. (2006). Long-Term Efficacy of Three Contraceptive Approaches for Population Control of Wild Horses. USDA National Wildlife Research Center - Staff Publications.

Kirkpatrick, J. F., Liu, I. M. K., Turner, J. W., Naugle, R., & Keiper, R. (1992). LONG-TERM EFFECTS OF PORCINE ZONAE-PELLUCIDAE IMMUNOCONTRACEPTION ON OVARIAN-FUNCTION IN FERAL HORSES (EQUUS-CABALLUS). Journal of Reproduction and Fertility, 94(2), 437-444.  Retrieved from <Go to ISI>://WOS:A1992HR77000018

Kirkpatrick, J. F., Rowan, A., Lamberski, N., Wallace, R., Frank, K., & Lyda, R. (2009). The practical side of immunocontraception: zona proteins and wildlife. Journal of Reproductive Immunology, 83(1-2), 151-157. doi:10.1016/j.jri.2009.06.257

Lyda, R. O., Hall, J. R., & Kirkpatrick, J. F. (2005). A comparison of Freund's Complete and Freund's Modified Adjuvants used with a contraceptive vaccine in wild horses (Equus caballus). J Zoo Wildl Med, 36(4), 610-616. doi:10.1638/04104.1

National Research Council, (2013). Using Science to Improve the BLM Wild Horse and Burro Program: A Way Forward. PDF accessed 01/12/16: http://www.nap.edu/catalog/13511/using-science-to-improve-the-blm-wild-horse-and-burro-program.

Phraluk, Orasa; Wajjwalku, Worawidh; Siriaroonrat, Boripat; Booddee, Orawan; Thongtip, Nikorn. (2015). Effects of immunization against gonadotropin releasing hormone on reproductive functions in male rusa deer (Rusa timorensis). The Thai Journal of Veterinary Medicine 45.1   (Mar 2015): 1,3-10.

Ransom, J.,   Roelle, J.,  Cade, B., Coates-Markle, L., Kane, A., Ransom, Jason I., Roelle, James E., Cade, Brian S., Coates-Markle, L., & Kane, A. (2011) Foaling Rates in Feral Horses Treated With the Immunocontraceptive Porcine Zona Pellucida. WILDLIFE SOCIETY BULLETIN.

Ransom, J. I., Hobbs, N. T., & Bruemmer, J. (2013). Contraception can Lead to Trophic Asynchrony between Birth Pulse and Resources. Plos One, 8(1). doi:10.1371/journal.pone.0054972

Ransom, J. I., Powers, J. G., Garbe, H. M., Oehler Sr, M. W., Nett, T. M., & Baker, D. L. (2014). Behavior of feral horses in response to culling and GnRH immunocontraception. Applied Animal Behaviour Science, 157, 81-92. doi:http://dx.doi.org/10.1016/j.applanim.2014.05.002

Speroff, L., & Fritz, M. (2012). Clinical Gynecologic Endocrinology and Infertility (8th ed.). New Yok: Lippincott Williams & Wilkins.

Turner, J. W., Liu, I. K. M., Flanagan, D. R., & Rutberg, A. T. (2007). Immunocontraception in wild horses: One inoculation provides two years of infertility. Journal of Wildlife Management, 71(2), 662-667. doi:10.2193/2005-779

Zhanwei, S. (1989). Chemical castration of horses and mules by injecting testis with iodine tincture. Journal of Liaoning Animal Husbandry and Veterinary Medicine.

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Other resources:

Barber, M. R., Lee, S. M., & Fayrer-Hosken, R. A. (1998). Staining patterns to the zona pellucida of the dog, cat, horse and elephant with porcine zona pellucida (pZP) antisera. Theriogenology, 49(1), 307-307. doi:10.1016/s0093-691x(98)90660-4

Barber, M. R., Lee, S. M., Steffens, W. L., Ard, M., & Fayrer-Hosken, R. A. (2001). 

Immunolocatiom of zona pellucida antigens in the ovarian follicle of dogs, cats, horses and elephants. Theriogenology, 55(8), 1705-1717. doi:10.1016/s0093-691x(01)00514-3

Berger, J. (1983). Induced abortion and social factors in wild horses. Nature, 303(5912), 59-61.  Retrieved from http://dx.doi.org/10.1038/303059a0

Bowling, A. T., & Touchberry, R. W. (1990). Parentage of Great Basin Feral Horses. The Journal of Wildlife Management, 54(3), 424-429. doi:10.2307/3809652

Duncan, P. (1982). Foal killing by stallions. Applied Animal Ethology, 8(6), 567-570. doi:http://dx.doi.org/10.1016/0304-3762(82)90221-8

Feh, C. (1990). Long-term paternity data in relation to different aspects of rank for camargue stallions, Equus caballus. Animal Behaviour, 40(5), 995-996. doi:http://dx.doi.org/10.1016/S0003-3472(05)81007-3

Feh, C., & Munkhtuya, B. (2008). Male infanticide and paternity analyses in a socially natural herd of Przewalski's horses: sexual selection? Behav Processes, 78(3), 335-339. doi:10.1016/j.beproc.2007.12.009

Gray, M. E. (2009). An infanticide attempt by a free-roaming feral stallion (Equus caballus). Biol Lett, 5(1), 23-25. doi:10.1098/rsbl.2008.0571

Gray, M. E., & Cameron, E. Z. (2010). Does contraceptive treatment in wildlife result in side effects? A review of quantitative and anecdotal evidence. Reproduction, 139(1), 45-55. doi:10.1530/rep-08-0456

Gray, M. E., Thain, D. S., Cameron, E. Z., & Miller, L. A. (2010). Multi-year fertility reduction in free-roaming feral horses with single-injection immunocontraceptive formulations. Wildlife Research, 37(6), 475-481. doi:10.1071/wr09175

Jordana, J., Pares, P. M., & Sanchez, A. (1995). ANALYSIS OF GENETIC-RELATIONSHIPS IN HORSE BREEDS. Journal of Equine Veterinary Science, 15(7), 320-328. doi:10.1016/s0737-0806(06)81738-7

Kavar, T., & Dovc, P. (2008). Domestication of the horse: Genetic relationships between domestic and wild horses. Livestock Science, 116(1-3), 1-14. doi:10.1016/j.livsci.2008.03.002

Kirkpatrick, J. F., Liu, I. M. K., Turner, J. W., Naugle, R., & Keiper, R. (1992). LONG-TERM EFFECTS OF PORCINE ZONAE-PELLUCIDAE IMMUNOCONTRACEPTION ON OVARIAN-FUNCTION IN FERAL HORSES (EQUUS-CABALLUS). Journal of Reproduction and Fertility, 94(2), 437-444.  Retrieved from <Go to ISI>://WOS:A1992HR77000018

Kirkpatrick, J. F., Rowan, A., Lamberski, N., Wallace, R., Frank, K., & Lyda, R. (2009). The practical side of immunocontraception: zona proteins and wildlife. Journal of Reproductive Immunology, 83(1-2), 151-157. doi:10.1016/j.jri.2009.06.257

Kirkpatrick, J. F., & Turner, A. (2002). Reversibility of action and safety during pregnancy of immunization against porcine zona pellucida in wild mares (Equus caballus). Reproduction (Cambridge, England) Supplement, 60, 197-202.  Retrieved from http://europepmc.org/abstract/MED/12220160

Linklater, W. L., Cameron, E. Z., Minot, E. O., & Stafford, K. J. (1999). Stallion harassment and the mating system of horses. Anim Behav, 58(2), 295-306. doi:10.1006/anbe.1999.1155

Linklater, W. L., Cameron, E. Z., Stafford, K. J., & Minot, E. O. (2013). Removal experiments indicate that subordinate stallions are not helpers. Behav Processes, 94, 1-4. doi:http://dx.doi.org/10.1016/j.beproc.2013.02.005

Lyda, R. O., Hall, J. R., & Kirkpatrick, J. F. (2005). A comparison of Freund's Complete and Freund's Modified Adjuvants used with a contraceptive vaccine in wild horses (Equus caballus). J Zoo Wildl Med, 36(4), 610-616. doi:10.1638/04104.1

Madosky, J. M., Rubenstein, D. I., Howard, J. J., & Stuska, S. (2010). The effects of immunocontraception on harem fidelity in a feral horse (Equus caballus) population. Applied Animal Behaviour Science, 128(1–4), 50-56. doi:http://dx.doi.org/10.1016/j.applanim.2010.09.013

Mask, T. A., Schoenecker, K. A., Kane, A. J., Ransom, J. I., & Bruemmer, J. E. (2015). Serum antibody immunoreactivity to equine zona protein after SpayVac vaccination. Theriogenology, 84(2), 261-267. doi:10.1016/j.theriogenology.2015.03.012

Massei, G., & Cowan, D. (2014). Fertility control to mitigate human-wildlife conflicts: a review. Wildlife Research, 41(1), 1-21. doi:10.1071/wr13141

Nuñez, C. M. V., Adelman, J. S., Mason, C., & Rubenstein, D. I. (2009). Immunocontraception decreases group fidelity in a feral horse population during the non-breeding season. Applied Animal Behaviour Science, 117(1–2), 74-83. doi:http://dx.doi.org/10.1016/j.applanim.2008.12.001

Pluhacek, J., & Bartos, L. (2000). Male infanticide in captive plains zebra, Equus burchelli. Anim Behav, 59(4), 689-694. doi:10.1006/anbe.1999.1371

Ransom, J. I., Hobbs, N. T., & Bruemmer, J. (2013). Contraception can Lead to Trophic Asynchrony between Birth Pulse and Resources. Plos One, 8(1). doi:10.1371/journal.pone.0054972

Ransom, J. I., Powers, J. G., Garbe, H. M., Oehler Sr, M. W., Nett, T. M., & Baker, D. L. (2014). Behavior of feral horses in response to culling and GnRH immunocontraception. Applied Animal Behaviour Science, 157, 81-92. doi:http://dx.doi.org/10.1016/j.applanim.2014.05.002

Schulman, M. L., Botha, A. E., Muenscher, S. B., Annandale, C. H., Guthrie, A. J., & Bertschinger, H. J. (2013). Reversibility of the effects of GnRH-vaccination used to suppress reproductive function in mares. Equine Veterinary Journal, 45(1), 111-113. doi:10.1111/j.2042-3306.2012.00577.x

Speroff, L., & Fritz, M. (2012). Clinical Gynecologic Endocrinology and Infertility (8th ed.). New Yok: Lippincott Williams & Wilkins.

Turner, J. W., Liu, I. K. M., Flanagan, D. R., & Rutberg, A. T. (2007). Immunocontraception in wild horses: One inoculation provides two years of infertility. Journal of Wildlife Management, 71(2), 662-667. doi:10.2193/2005-779

Primitive Markings in Dun Horses

The Primitive Markings

 © Equus ferus- Wild Horse Photography & Karen McLain Studio

Primitive markings refer to stripes and lines darker than the coat colour that appear on horses carrying the Dun trait (Dn⁺). The most common marking is a dorsal stripe also called a lineback. The line travels from the mane, down the back and into the tail. Many horses have a dorsal stripe but in duns, the stripe extends from the mane through the tail. There is some debate as to whether the Dun factor- the lightening of red and black on the body- is linked to a separate gene causing the primitive marking, or if they are on the same gene.

Dr. Sponenberg states that if the Dun factor and the primitive markings were located on separate genes, we would see far more horses with primitive markings who are not Duns and more Dun horses without primitive markings (Sponenberg, 2009). Neither of those situations commonly occur, so the traits are most likely located on the same gene. 

© Equus ferus- Wild Horse Photography & Karen McLain Studio

Other makings are zebra stripes on the legs, shoulder or wither stripes- some extending up the neck. Cobwebbing- or facial markings are the rarest. It is extremely rare to find a Dun without a dorsal stripe and zebra stripes are usually present but may be so pale they are not detectable except under certain circumstances. 

© Equus ferus- Wild Horse Photography & Karen McLain Studio

Guard hairs- or lighter hairs on either side of the mane may occur (see photo to the right). Horse Management Areas with a large Dun populations are Sand Wash Basin in Colorado, and Pryor Mountain in Montana, amongst others. There may be darker edges to the ears and mottling/striping on the chest or sides. The Dun factor lightens the body leaving the 'points' or lower legs, mane, and tail darker. The head is also left darker which can cause confusion when separating Duns from Roans. The Blue Roan in the photo on the right may have the Dun factor in addition to the Roan which makes identification even more challenging.

© Equus ferus- Wild Horse Photography & Karen McLain Studio

The primitive markings are found on some of the oldest horse breeds such as Sorraia, Icelandic horses, and Norwegian Fjords. They are also seen on Przewalski's Horse. However, the Dun trait is also seen on more modern breeds such as the Quarter Horse, Spanish Horse breeds and European draft breeds (Stachurska, 1999). The presence of the Dun factor does not mean the horse is from an ancient lineage- the Dun trait is autosomal dominant. This means that if the parent is homozygous (DnDn) or heterozygous (Dndn)- they will have a dun coat and pass the dun trait on to 75% off their offspring making this inherited coat colour common in isolated populations.

Sponenberg, D. (1996). Equine color genetics. Ames: Iowa State University Press.

Stachurska, A. (1999). Inheritance of primitive markings in horses. Journal of Animal Breeding and Genetics, 29-38.

Assateague Island National Park 2015

Hello Everyone!!!
We're back at Assateague Island NP for a long weekend of photography.  Karen McLain has already been here for over a week as an "Artist-in-Residence". This is a prestigious appointment in which an artist, often a painter, is invited to spend a fortnight at a location and uses the opportunity to hone their artistic skill in a new environment and they often teach classes as well. 

I joined Karen today after driving down the coast from the Hudson Valley in New York. We shot a few of the ponies, although the conditions were less than optimal with an intermittent light mist falling. We broke early and had a wonderful dinner at a restaurant in Salisbury, Maryland called "Brew River"- the specialty was crab cakes and they did the cakes justice.  The oysters on the half-shell were amazing and we thoroughly enjoyed this dining experience.

It was also nice to see a horse that had been a foal, when we were last here in 2012. One of the things I particularly enjoy is seeing foals grow up and get bands of their own or give birth to their own foals. It lends a more personal aspect to the photography.

Foal 2015- Today

Foal 2012

Same foal today 2015

Tomorrow we are up early and plan to have a full day in the park. Karen is teaching a class for the Assateague Island Alliance on Saturday so we will prepare for that- a local paper did a nice segment of Karen's residency here . 

As always, continue sharing Equus ferus' photos! We will be posting live from the park.

The wild horses of the Salt River

In light of the recent uproar regarding the future of the Salt River Horses in Arizona, including the false alarm of a “round-up in progress”, I thought I'd take some time to jot a few things down. Bear in mind I am playing the devil's advocate in some of these comments and I firmly feel those horses deserve the right to live free at the River. I do not feel they represent a safety hazard to anyone nor have there been any negative incidents involving horse-human interactions. Cool heads need to prevail and present the facts clearly and calmly. 

The Salt River Horses of Arizona are in danger of losing their freedom. Advocates are scrambling to find rationales for preserving this beautiful population of wild horses. You may read that they are descendent of Spanish Colonial Horses and therefore they should be protected. Unfortunately, as soon as domestic horses were allowed to interbreed with the Salt River horses over the years, the lineage became diluted and their historical value diminished. There is no test currently, that allows us to differentiate a wild horse from a domestic horse. This is the principal reason the United States Department of Fish and Wildlife denied the recent petition to make the mustang an endangered species. We cannot tell them apart from domestic horses. The wild horses have no genetic mutations that are unique and therefore they cannot be isolated or differentiated from the domestic population. Even conformation isn't reliable as the wild horses are the result mixing different breeds and similarities as well as differences exist among both domestic and wild horses.

Other attempts at proving uniqueness are that the Salt River horses are the only horses that eat river grass. The consumption of aquatic vegetation is actually quite common in the the wild horses of Camargue region of France and in the ponies of Assateague and Chincoteague. So the “mermaid horses” or more correctly the hippocampus of the Salt River is mere fancy. Another point cited to set this population apart is that there are a lot of grey horses in the Salt River herds. Anyone who has been to Sand Wash Basin or Spring Creek Basin will tell you that there are a lot of grey horses at those horse management sites. It is a dominant color and therefore, rather common in every wild horse population. The presence of the dun color, which is frequent in the more ‘primitive’ or ancient breeds (such as Spanish Colonial Horses, Nordic breeds, and/or the horse’s wild cousin, Przewalski’s Horse) is present in the Salt River Horses, but duns are far more far more abundant in wild horse populations that are more isolated. The Pryor horses represent a more bottle-necked population and they have a large number of dun horses, more proportionally than the Salt River.

Instead of struggling to find characteristics which are unique to the horses of the Salt River, perhaps we ought to focus on what they represent. They represent freedom, they represent our heritage and they played a significant role in how the west was truly won. They are a beautiful addition to the landscape of Arizona and the Salt River would be empty without them. They remind us of the beauty of nature and they bring visitors to the Tonto National Forest every year. I have seen these beautiful horses and they have captivated me. Do whatever you can to help these horses. 

Change.org 

https://www.change.org/p/u-s-national-park-services-tonto-national-forest-stop-the-annihilation-of-the-salt-river-wild-horses-savewildhorses?recruiter=26216842&utm_source=share_petition&utm_medium=copylink

Senator John McCain, Phoenix office, 2201 East Camelback Road, Suite 115, Phoenix, AZ 85016. Main: (602) 952-2410 and Senator Jeff Flake. (P: 202-224-4521) 

http://www.mccain.senate.gov/public/index.cfm/contact-form

and

http://www.flake.senate.gov/public/index.cfm/contact-jeff

 Neil Boswell - Forest supervisor 602-225-5201

Carrie Templin, Public Affairs Officer, Tonto National Forest. 602-225-5290

Lethal White Syndrome LWS (Overo Lethal White Syndrome OLWS)

Equus ferus- Equine Coat Colour Genetic -LETHAL WHITE

One of the mares at the Sand Wash Basin was believed to have given birth to a foal with Lethal White Syndrome.  And although we cannot be absolutely sure the foal was a Lethal White foal, the behaviour strongly suggests it might have been. Lethal White Syndrome has been talked about in the groups and on Facebook, hence this blog post. Without a necropsy (autopsy on an animal) we won't know for certain but here is what we do know...

Similar to Hirschsprung's disease in humans, Lethal White Syndrome affects the colon by making it non-functional and in horses it also affects pigment of the coat. The affected foals are born pure white with blue/grey eyes and occasionally a smudge or darker colour on the body or near the tail however, they die within 72 hours of birth. The colon in these foals is a dead-end and the foals cannot pass feces. They do not act normally and exhibit signs of distress.

Lethal white foal (Picasso x Mingo) photo credit Nancy Roberts 2011

Picasso and Mingo 2012 photo credit Karen McLain

The trait, which is inherited, is carried by the horses who also carry the paint trait frame overo. Frame Overo horses typically have jagged white markings along the center of the body. The back and belly may remain solid colored so the effect is a framed area of white. They may have white faces (apron or bald face) and they may have blue eyes although not always. Some horses may minimally express the trait and the only evidence of the frame overo paint trait is a little spot of white along the neck and an unusually shaped blaze. Some horses may also carry other paint traits such as tobiano and they horses are referred to as toveros. Without genetic testing, nothing is certain so we are basing our assumptions on what we have observed and the reproductive history of the individual mustangs.

Yahtzee (R) & Van Gogh (L)
Photo credit Meredith Hudes-Lowder of Equus ferus Wild Horse Photography

In order to produce a foal with Lethal White Syndrome, both parents must be overo. Not all overo horses carry the trait according to the American Paint Horse Association (http://www.apha.com/breed/geneticsarticles/lethal-whites-1) and not all blue-eyed white foals carry the Lethal White gene. Because  Lethal White Syndrome is autosomal recessive, it means when two horses that are overo and each carry the gene , there is a 25% chance the foal with be born with the syndrome. If a dam with the trait and a sire with the trait have three normal foals, it does not mean the fourth foal will carry the trait; the chances a foal will inherit the syndrome resets each gestation and remains one in four with each subsequent preganncy. 
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In the Punnett Square below (Horse drawings by Karen McLain)
Oo outside the square on top represent the SIRE
Along the left side, the Oo represents the DAM
Both are Overo represented Oo and the carry the trait

The RESULT:
One Solid foal (unaffected) -25%
Two Overo foals- CARRIERS of the Lethal White Trait- 50%
One Lethal White Foal 25%

One Solid Foal (OO) 25%

Two Overo Foals (Oo) 50%

One Lethal White Foal (oo) 25%

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PUNNETT SQUARE REPRESENTING AUTOSOMAL RECESSIVE INHERITANCE

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The photos below are Danielle M. Williams and they show Fleck's foal. Fleck is frame overo and the father is believed to be Eagle, a minimally marked frame overo so it is quite possible the foal carries the Lethal White Syndrome.  Sometimes Lethal White Foals do have darker pigment on the muzzle but this foal is not hunched over in the typical posture of a horse in gastric distress however the witness/photographer Danielle did say the foal did not look well and laid down frequently. She said the foal was unable to stand for any length of time. This is consistent with Lethal White Syndrome and the foals with the disorder often roll from side to side. Another possibility is that the foal may have perished in the fight between the band stallion Eagle and Diego who took over part of the band. Stallion infanticide is unfortunately unavoidable and may be more common than previously thought. Regardless of the manner of death, it is heartbreaking to see a young life extinguished so soon.

Fleck and her foal
Photo by Danielle M. Williams

Fleck and her foal 
Photo by Danielle M. Williams

Fleck and her foal 
Photo by Danielle M. Williams

Please email Meredith with any questions regarding the genetic behind Lethal White Syndrome or horse colour genetic in general.
Equus ferus- Wild Horse Photography
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*Much thanks to Karen McLain, Heather Robson, Stella Trueblood, Aleta Wolf, Connie Wagner, Danielle M Williams, Nancy Roberts, John Wagner, Joe Tosh, Patrick Brennan, Patti Mosbey, Robin Wadams and all the people who watch observe these horses and report on their behaviour.

Meredith Hudes-Lowder WHNP-BC, MSN, BSN, RNC, BS Biology

Meredith received a Bachelor of Science Degree from Binghamton University with an emphasis in ethology and genetics. She received a Bachelor of Science in Nursing also from Binghamton and a Masters of Nursing in Perinatal/Women's Health from Stony Brook University. She currently practices medicine as a Nurse Practitioner in Manhattan for Advantage Care Physicians. She is also enrolled in the Doctoral program at Stony Brook and anticipates graduation in 2016 as a Doctorate of Nursing Practice. Her doctoral thesis is a research study on cervical cancer screening intervals. She is a member of several professional organizations and was inducted into Sigma Theta Tau- the nursing honor society in 2007.