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June 2018 - Equine Skin Tumors

Pose your questions concerning equine skin tumors for expert, Dr. Elizabeth Carr from Michigan State University, during the month of June.

Click here to read this month's questions and answers.


  1. I have a one-month-old foal and would like to know which dewormer would be safe to use for their age?

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    Parasite control has changed dramatically over the recent few years. There was a time when treatment for intestinal parasites involved toxic chemicals that could only be administered by a stomach tube. The advent of over-the-counter "paste dewormers" provided horse owners access to safe and effective treatments they could give without veterinary assistance. Unfortunately, there is a lot of parasite resistance to most of the available compounds, so they are not as effective as they once were. It is encouraging, though, that studies show adult horses demonstrate a high degree of natural immunity against intestinal parasites, over 80%, in some populations.  

    Good housekeeping, daily stall cleaning and composting manure, will keep parasite populations low. Most important, is to test both the mare and foal and treat only those individuals shedding parasite eggs. Judicious use of the drugs designed to kill intestinal parasites will help control rates of infestation and limit the development of resistance in these disease-causing organisms. Madison Seamans, DVM, MS, Kuna, ID

  2. My mare is on Nutrena Safe Choice and Cosequin Optimized with MSN. Her 2 and a half month old colt eats out of her bucket along with her. Is it safe for him to consume the Cosequin?

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    The Safe Choice feeds are labeled for mares and foals. The use of neutraceuticals, like Cosequin and others for treatment of arthritis in horses is controversial, but probably not toxic to foals. There have been a few studies suggesting that the active ingredients (glucosamine and chondroitin) in these products could cause problems in horses with insulin resistance/metabolic syndrome. The use of a low-starch feed suggests there may be some concern here, so these products should be used with caution. Madison Seamans, DVM, MS, Kuna, ID

  3. I have a 27-month-old paint filly. She stands 15 hands and weighs aprox. 1000 lbs. I weigh 145 lbs. and ride her with a bareback pad in the San Francisco East Bay hills. I am wondering how many miles of walking/jogging these hills are safe for her? I have walked these hills with her for hundreds of miles before I started riding her.

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    The main concern for riding young horses is how it will effect joints and bone growth. Traditionally, the growth plates above the carpus (knees) has been considered critical, and hard riding should not be started until these areas have "closed". This can be easily determined by your equine veterinarian with a radiograph (x-ray) of the knees.

    Some recent studies indicate that two-year-old horses in light to moderate work will have increased bone density in their third year, and thus they are probably healthier than if they had not been worked. With this in mind, radiograph her knees to be on the safe side, and, if the growth plates are closed, put her to work. Unlimited long slow rides of walk/trot will probably benefit her, and the hills should provide an extra advantage for cardiovascular health. It will be fun for you and healthy for her. Madison Seamans, DVM, MS, Kuna, ID

  4. Can I use chia seeds instead of psyllium to prevent sand colic for my horses? Is it safe for pregnant mares?

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    Psyllium husks have been added to human diets (Metamucil, for example) for the laxative qualities found in the plant fibers called structural carbohydrates. Structural carbohydrates have no chemical or pharmacologic effect, but like a bran muffin, they can have relatively powerful laxative properties in animals on a low fiber diet (like us, for example). It is likely the same for structural carbohydrates of many seeds, whether chia, oat or wheat bran. 

    In contrast, the average thousand pound horse has 35 gallons of ground up hay and water in the digestive tract. The solids in this mixture are mostly fiber. With this in mind, the addition of a few cups of chia or psyllium fiber to the large amount of plant fiber already present in the equine gut will have little, if any, effect. Though the chia or psyllium husks probably won't hurt the horse, pregnant or not, there have been no controlled studies published that conclusively demonstrate these products prevent sand colic. Madison Seamans, DVM, MS, Kuna, ID

  5. My horse had a foal four days ago in which we had no idea she was pregnant. We just purchased her in May and she has had an all grass diet. I wonder if we should be doing anything for her or the foal. Should we have started giving her grain after she had the foal? Also, the foal has brown stains on its buttocks from manure that looks like diarrhea. Should we also be treating it for anything?

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    A well baby exam is always a good idea, especially in cases like this with no history of the mare's prepartum care (before the foal was born). The foal is exhibiting diarrhea, and this can be an early sign of neonatal septicemia. Even if the foal appears healthy, his condition can decline rapidly. Your equine veterinarian can exam both your mare and foal to provide a good assessment of the foal's health. A complete blood count on the foal can detect the presence of infection and a test for antibodies called IgG can be a good measure of his immune system. This should be done today or as soon as possible! Madison Seamans, DVM, MS, Kuna, ID 

  6. I adopted a mustang colt that had a cough and bloated belly. I found over 100 roundworms in his manure when I dewormed him! I need advice on a deworming schedule to control roundworms.

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    Roundworms can be a problem in young horses, and yours gave clear evidence of this by his response to the deworming. Although most adult horses are naturally immune to intestinal parasites, the potential for infestation cannot be ignored. There are four compounds available over the counter, which may be helpful in controlling intestinal parasites. Unfortunately, there is significant resistance in the parasite population to most of these drugs. 

    With this in mind, our approach to parasite control has changed over the recent few years. A "deworming schedule" should be dictated by the presence of infestation in each individual horse. This is determined by a simple, inexpensive lab test (that your veterinarian can perform) to identify parasite eggs shed in manure. By treating only those horses with positive fecal tests, we can selectively and efficiently control parasite populations in our horses, and possibly curtail parasite resistance to our very limited choice of treatments.   

    Although it appears that your treatment helped your colt, a fecal sample (one fresh fecal ball is plenty) should be tested to make sure your colt is clean. An additional test should be run in six months, and repeated annually as a part of his routine vaccination and dental care. Although there are exceptions, without laboratory evidence of parasitism, "routine deworming" is not recommended. Madison Seamans, DVM, MS, Kuna, ID 

  7. I have a 7-day-old foal. Can I use a delution of Dawn dish soap as fly spray?

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    Although detergents may be considered "safe", as they are used routinely all over the world, it should be remembered that they are very caustic substances. This is why these products must be thoroughly rinsed from all surfaces. Left on the skin, detergents can cause severe irritation. Left on dishes, they can cause very unpleasant gastric upset. With this in mind, detergents should not be our first choice in fly repellents, no matter what the dilution, in a foal. Madison Seamans, DVM, MS, Kuna, ID

  8. What effect does chia seeds have on foals?

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    There are anecdotal reports of some weight loss in people eating chia seeds from the Salvia plant, a type of mint from South America. Seeds from this genus of plant appear in the diets of many indigenous people in the western hemisphere and extracts of it are used in some traditional Chinese medicines. Chia seeds are a good source of omega-3 fatty acids, as are flax and other whole seeds, but there are no controlled studies about their effects on foals. As the mare's milk is the perfect diet for a foal, supplementation with chia seeds is probably not beneficial. Madison Seamans, DVM, MS, Kuna, ID

  9. I have a 12-year-old maiden mare with navicular syndrome in her right front hoof. She is a retired barrel racing horse. She does have a slight limp but can still lope around and play. I am considering breeding her but would like your opinion on her condition and caring a foal to term.

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    The link between genetics and disease in horses has long been argued, but seldom proven. Problems with the navicular bone have been the subject of much research, speculation and more than a few name changes over the years (hence the term: navicular "syndrome")  A genetic origin for factors predisposing lameness is still unclear, but when we think of the astounding complexity by which various traits are passed down through the generations, the factors "in the blood" cannot be ignored. As the endurance of the Arabian, the speed of the Thoroughbred and the "cow" of the Quarter Horse are obviously inherited traits, can we ignore the potential genetics of less desirable attributes?   

    If we consider the various criteria for selecting a horse, one question we should be asking: Is lameness in a young horse an acceptable trait? If the "unwanted" trait influences the intended activity, should it be retained? For example, if we want to show paint or buckskin horses, color is an obvious necessity. Color may not influence speed, but lameness surely will.  

    If we were looking to buy a colt as a barrel horse "prospect" would we consider one from a dam that was retired early due to navicular problems? Many top barrel horses compete in their late teens and early twenties. If our goal is to produce horses that are better than those we ride today, do we want to start with problems? Maybe we should consider beginning with the best, and work to improve them.  Madison Seamans, DVM, MS, Kuna, ID 

  10. I have a mare that had physitis as a weanling. She had a foal last year and he has developed physitis as a weanling also. Is physitis hereditary? Does stallion choice make any difference (I am thinking of using the same stallion this year), or is it just shear coincidence that they both have it?

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    Epiphysitis (aka. physitis) is one of a number of developmental orthopedic diseases in horses, and it is the most forgiving--most horses grow out of it. The most likely cause is nutrition, and it suggests that you may be feeding too well. You may want to consider changing your feeding program, and your equine veterinarian can be a great resource for this type of problem. It is probably not genetic. Madison Seamans, DVM, MS, Kuna, ID

  11. At what months should you give a pregnant mare Pneumabort K+1B shots?

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    The standard protocol for the "rhino" shots to prevent viral abortion has always been at 5, 7 and 9 months of gestation. However,  the most important vaccine should be given about a month before the mare is due to deliver. The sleeping sickness series (Eastern and Western Encephalomyelitis, and West Nile Virus) with tetanus. This gives the foal a boost to his immunity through the colostrum, or first milk, nursed during the first 12 hours of life. Madison Seamans, DVM, MS, Kuna, ID

  12. Our new Arabian colt is 9 weeks old. He is tall and beefy; healthy and full of energy. One issue: He will not eat horse feed. Mom pretty much guarded her bucket since he was born and while she eats, he stands quietly at her side, or checks out the hay pile. He does eat hay and graze, but I know he needs to be chowing down by the time we wean. We have tried a variety of feeds (foal feeds, milk replacement pellets, alfalfa pellets) and oats. All we get is a flem response! Advice please - worry or chill? 

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    Mare's milk is the perfect ration for a foal, as it provides all the nutrients he needs in the precise amounts required and it is available twenty-four hours a day. The fact that he is eating hay on his own is a good indication that all his parts are functioning properly. Once he figures out just how GOOD grain is, your problem will likely be one of limiting his consumption, rather than encouraging it. We should be careful not to over feed young, growing colts as this can produce developmental orthopedic diseases that may be difficult to reverse. Mom and hay are adequate for now, so yes, chill. Madison Seamans, DVM, MS, Kuna, ID

  13. I have a 2-year-old, 36" stud that I just acquired and is cryptorchid. I have been told it is quite an extensive surgery, hence why he was passed around and ended up with me. Can you tell me about the condition, the procedure for surgery and cost?

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    Cryptorchidism is the absence of both testicles in the scrotum. During development, the tissues in the embryo that become the ovary or testis are part of what will become the kidney. Later in the process, but before birth, the testis descends to the scrotum. In almost all cases, a colt born a cryptorchid will stay that way. The challenges here are three-fold.

    1.) What will happen if we leave him alone? The retained testis is not capable of making sperm cells, but it will still produce the male hormones. Removing the normal, scrotal testis will result in a horse that is sterile and looks like a gelding, but acts like a stallion. There are some reports to suggest that retained testicles in the dog may become cancerous, but there is no conclusive connection with cancer and retained testicles in the horse. So a horse with one testicle in the right place is just as fertile as he would be with two. 

    2.) Is there a treatment? Yes. The use of a hormone known as human chorionic gonadotropin (HCG) has been used successfully to stimulate descent of a retained testicle. This begs the question, if this is a genetic defect, should it be treated if there is a chance it will be passed on to future generations. Some breed associations have no prejudice against cryptorchidism, and call these horses “ridgelings”. A study published many years ago tracked the offspring of three “ridgeling” stallions and compared them with normal stallions in a similar population. The “normal” stallions produced slightly more cryptorchid colts in this study. This does not conclusively answer the genetic question, but suggests that the problem involves more than just inheritance.

    3.) What is the surgery and what is the cost? All veterinary costs have regional and facility variations. Some practitioners attempt this procedure in the field, while others prefer performing this potentially complicated surgery in a sterile, hospital setting. In these patients, the retained testicle can be anywhere from just inside the belly wall, to near the kidney. This distance (up to three feet) can present surgical challenges in many cases. Therefore, the cost is considerably more than a routine castration. Varying with region, the type of facility and surgeons involved, this operation can run five to ten times the cost of a normal castration. Madison Seamans, DVM, MS, Kuna, ID

  14. Is there a risk if foals have access to salt blocks? I have heard that they can become “addicted” to the salt and if they eat too much and die from it. I have also heard that their kidneys cannot cope with the salt until they are six months old. Is this true?

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    The use of dietary supplements of any kind, including salt, is somewhat controversial. Mare’s milk contains all the nutrients, including minerals like sodium and chloride (the elements that make up salt) necessary for a growing foal. So a salt block for a foal is probably not necessary. Many mares will have access to a salt block, so if the mare is licking the salt block, the foal probably will, too. True “salt toxicity” is actually due to water deprivation, so it would be very rare for salt to become toxic as long as the horses have access to free choice water.     

    The foal’s internal organs undergo remarkable changes immediately after birth. Heart, lung, liver and kidney complete an amazing transition from the pre-natal life, when the maternal system takes care of everything, to post-natal life, where the foal’s body must function on its own. In a normal foal, the competency of the kidney should be established by the first few hours of life, and thus. Madison Seamans, DVM, MS, Kuna, ID

  15. I have a 21-year-old FQH mare that has never been bred. Is it possible to harvest her eggs and do an embryo transplant?

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    Maybe. This is really two questions. Embryo transfer involves breeding the mare, flushing the fertilized ovum seven days after ovulation and transferring it to a recipient mare. Harvesting eggs involves removing unfertilized ova (eggs) from the ovary, and supplying the sperm cells via one of several different techniques.

    Let’s start with embryo transfer. In young, fertile mares, flushing embryos is a relatively simple procedure that is offered by many veterinary practices. The mares are bred naturally or artificially, their cycle closely monitored via ultrasound so the uterus can be flushed seven days after ovulation. The harvested embryo is placed in the uterus of a recipient mare that has ovulated on about the same day, but not bred. This procedure is quite successful if both mares have normal reproductive systems. In older mares, however, this can become a challenge. 

    Reproductive efficiency begins to decline in mares after the age of about 13 years. Although a twenty-one-year-old mare may be in perfect health in every other way, her reproductive competence is limited.   

    Producing a viable embryo is a process that may be more difficult than it sounds. The mare’s ability to get pregnant is first dependent on her ability to produce fertile ova (eggs). Stallions produce billions of new sperm cells most every day of their adult lives. Mares, however, are born with all the eggs they will ever have, so an aged mare has aged ova that may not function as well as they did earlier in her life. In addition, she must have normal anatomy and physiology of her cervix, uterus and uterine tube. Aging can compromise all or part of this process, and thus prevent the production of a viable embryo. 

    There are many tests that can be performed to determine potential fertility in mares. A culture of the uterine fluids during the first two days of heat can detect the presence of infection that will not affect her general health, but will greatly impair fertility. An endometrial biopsy of the lining of her uterus can give us more information about reproductive health. Hormone analysis can be of some use to determine her ability ovulate normally and support an embryo during early development. However, the most accurate test will be to breed her and see if an embryo can be flushed. In mares that cannot produce an embryo, another option is available.

    Oocyte transfer: A needle is inserted into the structure on the ovary, which contains the egg (The ovarian follicle) and the fluid containing the ovum is aspirated and placed into a dish containing culture medium. Ova harvested in this manner can be used for in vitro fertilization (test tube babies), or transferred to the uterine tube of younger mare to be bred in the same cycle (gamete intrafallopian transfer, the “GIFT” procedure).

    During the recent decade, our understanding of equine reproduction has greatly expanded. With this new knowledge, technology has been developed to prolong the productive years of our favorite mares, and helped to preserve valuable genetic resources for the equine industry. These procedures are not cheap and the success rate in older mares is not high--there are no guarantees--but they do provide options for mare owners that previously had none. Madison Seamans, DVM, MS, Kuna, ID