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Extension > Horse Extension - Ask an Expert > March 2012

Tuesday, March 13, 2012

Is there any danger in horses grazing frosted pastures in the fall?

Q: Is there any danger in horses grazing frosted pastures in the fall? If so, how long would you wait?

A: Some deciduous leaves can be deadly after a frost or after they have wilted due to broken branches, fall leaf shed or storm damage. Leaves of greatest concern for horses are wilted maple and prunus species, including chokecherry, ornamental almond, and cherry trees. Horse owners should identify all such seasonally toxic trees on the property, and keep horses from their fallen or frost damaged leaves for at least 30 days. Even though these leaves are not commonly eaten, horses can accidentally ingest them, especially if hungry or bored.

Cyanide toxicity can also be an issue after frost. There are no reports of toxicity of horses grazing frost damaged grass, alfalfa, or clover. However, frost damaged pasture forages can have higher concentrations of sugars, leading to an increase in potential for founder and colic. To reduce the chance of adverse health effects, it is recommend that horse owners wait up to a week before turning horses back onto a pasture after a killing frost.

By Krishona Martinson, PhD, University of Minnesota

Why is snow not a suitable source of water for horses?

Q: Why is snow not a suitable source of water for horses? Don't wild horses live on snow?

A: First of all, according to Chapter 346 in the MN Pet and Companion Animal Welfare Act, "equines must be provided with clean, potable water in sufficient quantity to satisfy the animal's needs or supplied by free choice". Snow or ice is not an adequate water source. There have been a few scientific studies that show some horses who are acclimated to winter weather conditions can receive their water requirements from snow.

However, there are serious health risks associated with snow consumption, including the adjustment period as horses learn to ingest snow, the actual water content of the snow, and total water intake. Some wild horses can receive their water needs from snow, but the risk of gastrointestinal tract problems, colic, and reduced feed intake is significant for domesticated horses. Relying on snow as the source of water for domesticated horse in Minnesota is illegal and not recommended.

By M. Hathaway, PhD & J.Wilson, DVM, University of Minnesota

Why is my thoroughbred collapsing?

Q: I have an off the track thoroughbred who collapses periodically. I have had him since November and he has gone down twice in the cross ties and once by the mounting block. He is 8 years old and approximately 17 hands. I recreated the situation and discovered that if I tighten the girth he goes down. He has not done this with me riding him. I do not think this is behavioral. I am just looking for directions and answers.

A: Some horses develop this odd form of collapse when they elevate their heads or when the girth is tightened without it being a specific medical issue. Sometimes muscle soreness is involved. The collapse could also be a result of sore withers, ribs fractured, or fainting from cardiac issues. I would recommend a complete physical for the horse. During the physical, I would also recommend you tightening the girth while the veterinarian watches to see if there are other areas that need exploration.

By Stephanie Valberg, DVM, PhD, University of Minnesota

Is a high frequency rodent controller safe to put in my horse barn?

Q: I purchased a high frequency rodent controller (puts out high frequency sounds to deter mice, rats, etc...). I would like to know if it is safe to put in my horse barn? The box says it is safe for "pets", but does not mention horses. Will the high frequency harm my horses or "drive them crazy"?

A: We are not aware of any research that specifically addresses this issue. Have you contacted the manufacture of this product with your question? Horses do hear better than we (humans) do at high frequencies, but so do dogs and cats. If the manufacture says the product is safe for use around horses, we recommend trying the product further away from the horses at first, and then gradually moving it closer if the horses do not seem to react. We would encourage that while trying the product, someone is watching the horses and the horses have a way to evacuate the area. Finally, watch for any behavior or eating changes while using this product and stop using it immediately if you observe any adverse reactions.

By J. Wilson, DVM and E. Malone, DVM, University of Minnesota

What can excessive levels of iron do to horses?

Q: I have water that has tested very high for iron (unsafe to drink). The well is located in an agricultural field, and used to irrigate a hay field that is then harvested and fed to my horses. Will the high levels of iron from the irrigated water be taken up by the hay and then transferred to the horses? What can excessive levels of iron do to horses? Can you test for iron levels in hay?

A: The National Research Council's maximum for iron is 500 mg/kg in the total diet for most species. Problems with equines have been observed when iron levels are above 1,000 mg/kg in the diet, and significant problems may exist when pastures grasses/hays are above 1,500‐ 2,000 mg/kg. There have been some cases where excessive iron in the forage has created interference in absorption and utilization of other trace minerals. Forage can be tested for iron levels. Equi-Analytical can test for iron. Other forage labs may also be able to perform the test if requested. Farms with excessive iron levels in water or forage can observe higher than normal incidence of developmental orthopedic disease in foals and yearlings. Interference may have been impacting copper, zinc and manganese utilization as well. Because it is not always feasible to move horses off high iron pastures (or water sources), adjust trace mineral intake and source to compensate for the high iron.

By Roy Johnson, Cargill

Can I feed both alfalfa hay and alfalfa pasture?

Q: What is your opinion on feeding both alfalfa hay and alfalfa pasture for horses?

A: Forage (hay and/or pasture) should be the backbone of a horse's diet, with at least half of the diet being some type of forage. Alfalfa is an excellent forage for most livestock, but the forage quality of good alfalfa hay and pasture exceeds the nutritional needs for most horses.

The average adult horse (lightly worked or ridden) needs about 10% crude protein in their diet. The crude protein in most good quality alfalfa hays and pastures vastly exceeds 10%. Although feeding excess protein to horses does not result in any short term health problems, it can lead to strong smelling urine (a concern if the horses are stalled in a barn) and can contribute to weight gain. If buying hay, hay with higher protein levels usually demands a higher price. Numerous horse owners are paying a premium for protein that is not needed by their animals.

Alfalfa hays and pastures also have higher digestible energy (DE) compared to grass hays and pastures. DE is used to balance the energy portion of a horse's diet. Feeding alfalfa hay and pasture to the average horse will most likely result in significant weight gain. Horse health problems tied to excessive weight gain include Cushing's, metabolic syndrome, laminitis or founder, and insulin resistance. The potential for excessive weight gain is the major drawback for feeding a high quantity of alfalfa to horses. Mares that are lactating or in late term gestation, or horses that are in an intensive training program would most likely benefit from adding some alfalfa to their diet because of the increased energy.

Calcium (Ca) and Phosphorus (P) is critical to bone and tissue formation in horses. For the average adult horse, the Ca:P ratio should be between 3:1 to 1:1. A benefit of having alfalfa as part of your forage is that alfalfa hays and pastures tend to have higher calcium levels relative to phosphorus, and have higher Ca levels than most grass hays and pastures. It is important to have your forage and grain tested to ensure the Ca:P is adequate and never inverted, especially in young, growing foals.

Not only will horses likely gain weight on pastures with a high quantity of alfalfa, but there are also pasture management practices to consider (i.e. no chemical weed control options) when alfalfa is included in pasture mixes. Horses are selective grazers. Some research studies have shown that horses prefer alfalfa over grasses in a pasture. In a mixed grass - alfalfa pasture, horses will actually choose to continuously graze the alfalfa, while leaving the grasses. However, most varieties of alfalfa will not withstand continuous grazing causing it to be short lived in a pasture. To extend the life of alfalfa in a pasture, choose a variety that is recommended for grazing. Be sure to rest the pasture and allow regrowth of both alfalfa and grasses.

Bottom line, alfalfa is an excellent forage, but should not be fed as the sole forage or in high quantities to the average adult horse because of the potential for excessive weight gain and the negative health effects tied to weight gain. Feeding alfalfa (not usually as the sole forage, but in higher quantities) can be useful for classes of horses that require additional energy, including lactating mares and horses in intensive training programs.

By K. Martinson, PhD, University of Minnesota

Should I worry about antibiotic resistant bacteria?

Q: I have been seeing more about the antibiotic resistant super bugs in people. Is this something I should worry about if my horse goes to the hospital?

A: Unfortunately, bacteria are becoming more resistant to antibiotics. This is true in both people and livestock, including horses. Over the past decades, multidrug resistant bacteria have been identified in horses. This includes multidrug resistant Salmonella and methicillin resistant Staph aureus (or MRSA).

These particular bacteria can cause serious illnesses in both horses and people. As such, we need to develop proactive steps to prevent the spread of these organisms, especially in our veterinary hospitals.

This includes isolating potentially contagious horses thorough disinfection and disease surveillance systems. Occasionally, these diseases have caused temporary closure of some veterinary hospitals. To avoid these problems it is important to use antibiotics under the supervision of a veterinarian, and promptly notify your veterinarian if you suspect a contagious illness in your horse, and separate your potentially ill horse from healthy herd mates. These steps will help catch outbreaks early and help protect herd mates.

At the University of Minnesota Veterinarian Medical Center, we have staff dedicated to disease surveillance and measures to prevent infections while in the hospital. These measures include:

  • Limiting foot traffic in certain areas of the hospital

  • Encouraging good hand washing

  • Disinfecting the environment

  • Monitoring cultures for these organisms

By Erin Malone, DVM, University of Minnesota

How do I treat sarcoids?

Q: I have a horse that has 4 small Sarcoids (pencil eraser size at the bottom of the ear). I put tree tea oil on them and thought they were gone, but over the winter they have come back. Do you have any info about Sarcoids? Specifically where they come from, how to treat them, nutrition information (if related), and are they genetic?

A: First, work with your local veterinarian to make sure your horse has sarcoids. Your local veterinarian should also be part of the treatment plan. Sarcoids are the most common skin tumor in horses and can be hard to cure. Sarcoids come in many different shapes and sizes, and the smaller ones are usually easier to cure. If you notice the sarcoids starting to grow larger, it is important that you start treating them immediately as they can get larger very quickly.

Sarcoids develop after exposure to cow pox virus (warts). Certain horses are probably genetically predisposed to getting sarcoids or are at a higher risk for developing sarcoids. There are multiple treatments that have been studied, and several treatments are effective. However, sarcoids frequently need repeated treatment as they can come back (as you've experienced).

I am not aware of any nutritional factors that lead to sarcoids or help in their treatment. For your specific situation, the sarcoids sound small, but are likely one large sarcoid under the skin with little areas that pop-up. I would recommend cryotherapy (liquid nitrogen), CO2 laser, or the drug Aldara. I'm not sure what is available in your area (in terms of freezing or burning the sarcoids), but because the sarcoids likely have tendrils, you might get the best results with the drug Aldara. Aldara is a prescription cream you can apply at home. Based on our research with Aldara, we recommend treating the sarcoids three times a week for the best outcome. Keep in mind it may take four months or longer to finish the treatment.

By Erin Malone, DVM, University of Minnesota

The information given is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Minnesota Extension is implied.

What caused my horse's intestines to hang out?

Q: Our 31 year old horse was found alive, but with his intestines hanging out. He was euthanized. What may have caused this? We had put out free salt with selenium just before the injury. Could the selenium have something to do with the horse's bowels protruding?

A: I am sorry to hear about your horse. I do not think it was due to the selenium. I can think of two scenarios. I suspect his intestines were coming out of his rectum. This is called a rectal prolapse and is usually due to straining. Various things can cause straining, including parasites, small colon impactions, rectal trauma, uroliths, neurologic disease, and tumors (very possible at his age). If horses push enough of their intestines out, they lose the blood supply to the intestines and the intestines die off. There is no easy fix for this and sometimes no possible fix.

The other scenario would be intestines coming out a hole in his body wall and skin. That is almost always due to trauma (wound).

If it was a rectal prolapse, I would recommend getting manure samples from the other horses and have them checked for parasites, even if they are on a good deworming program. If it was trauma and a wound in the horse's body wall, I would recommend you check the pasture/paddock for sharp objects.

By Erin Malone, DVM, University of Minnesota

Does drying corn eliminate mold?

Q: I have a barrel of ground corn that had been put through a dryer. My question is, with all the trouble farmers have been having with moldy corn, does the drying process eliminate the mold enough to use safely for mixing with horse feed?

A: It is important to remember that the presence of visible molds is only an indicator of a possible problem and that a sample needs to be analyzed to identified the mold type and amount to determine its potential negative impact. Drying corn to 14% moisture or less will inhibit mold growth, but does not necessarily kill the existing molds. Given favorable growing conditions of moisture above 15% and appropriate temperatures, molds can continue to grow. Also, drying does not eliminate mycotoxins from the corn. Mycotoxins in the corn before drying, will still be there after drying. Mycotoxins are diverse compounds produced by fungi (molds). However, not all mold produce mycotoxins. Gibberella, Aspergillus, Fusarium, and Penicillium are known to produce the following mycotoxins; vomitoxin (Gibberella), aflatoxin (Aspergillus), and fumonisin (Fusarium). Aflatoxins and fumonisins are detrimental mycotoxins with respect to equine performance, health, metabolism, and reproduction.

Aflatoxins have been shown to have severe adverse effects on horses. Clinical signs include weight loss, anorexia, poor body condition, increased body temperature and heart rate, lethargy, depression, lameness, and bilateral congestion of the eyes. Aflatoxins are more commonly found under hot and dry environmental conditions.

Horses are susceptible to the feeding of grains contaminated with fusarium mycotoxins. Dietary concentrations as low as 10 mg/kg of fumonisins are associated with fatal equine leukoencephalomalacia (ELEM). ELEM is a multifocal neurological disease of horses characterized by signs of depression, abnormal behavior, head pressing, ataxia, agitation, dementia, and blindness.

Testing moldy corn is critical. Even if mycotoxins are not present, feeding and palatability may still be affected. Most forage testing labs in Minnesota will also test for molds and mycotoxins.

By K. Martinson, PhD and J. Linn, PhD, University of Minnesota

What could be causing my horse's sore nose?

Q: I would like information on frostbite and sunburn during the winter months. I have a 7 year old black and white paint. He's had trouble with a sore nose which started in the fall. I've never had this problem with him before.

A: First have a veterinarian examine the horse (if you have not already). It is unlikely that frostbite and sunburn are the underlying issues for the sore nose. Frostbite on healthy, adult horses is rare. If frostbite is a problem, it's usually seen on the ears. Sunburn can be a problem as sunlight can reflect off of snow and cause a sun burn. However, this is much more common in higher altitudes.

A potential cause of the sore nose is photosensitization resulting from some type of liver damage or ingestion of poisonous plants. Examine your horse's hay and look for wild parsnip, a weed that commonly causes photosensitization and retains its toxic effect when dried in hay. In the fall, a certain mold (Cymodothea trifolii) that grows on legumes (alfalfa and clovers) can also cause photosensitization, which might help explain why you observed symptoms in the fall. The mold literally causes black blotches to occur on the underside of the clover leaves.

Treatments will depend on the cause of the photosensitization. Working with your veterinarian to diagnose and treat this problem is recommended.

More information on photosensitivity

By J. Wilson, DVM, C. Ward, DVM, and K. Martinson, PhD, University of Minnesota

How do I get rid of rain rot?

Q: I'm having problems with rain rot in my herd. I am treating it with a topical spray, but it will not go away. Do you have any suggestions?

A: Rain rot (if you are referring to dermatophilosis, a bacterial infection) is a common condition seen in horses during rainfall periods (since moisture predisposes the disease). Up to 80% of a herd can be affected. Important things to remember about management are:

  • Make sure you have the right diagnosis (other diseases can resemble rain rot)

  • It is very important to keep the horses dry

  • Most cases spontaneously regress within 4 weeks if the horses are kept dry

  • Crust/scabs removal and disposal is also helpful; crust removal may be painful and may require sedation.

  • Topical therapy can help. 2‐5% lime sulfur, 4% chlorhexidine solutions should be applied as total body shampoos or dips for about 5 consecutive days, then weekly until the scabs are healed. For the more localized lesions, use spray forms.

  • Sometimes systemic therapy is needed (antibiotic such as penicillin or potentiated sulfas) mainly for severe, generalized, or chronic cases.
Other things that should be considered (for treatment and control) are improved hygiene conditions and management practice, nutrition, and insect control measures in addition to avoidance of mechanical trauma to the skin (if any apply to your situation).

By Sandra Nogueira Koch, DVM, University of Minnesota

How can I stop my goats from eating my gelding's tail hair?

Q: I have an older gelding and 2 goats. They get along very well and are good companions. My problem is that the goats are eating the geldings tail hair. I have tried two different sprays, but the goats continue. I'm wondering if there is something else I could do?

A: First of all, evaluate the goat's diet and make sure it is not deficient in vitamins or minerals. Goats are browsers by nature and need to keep their mouths and minds busy. If you cannot, or do not want to, separate the animals, consider options, both homemade and commercial, that will make the horse's tail taste bad.

Homemade options include a mixture of dish soap and water, Vaseline and cayenne pepper, or Listerine. Hot pepper and Listerine should not be applied to or near the skin, just to the tail hairs that are within the goat's reach. Use gloves when mixing and applying the remedy. Commercial options include "Bitter Apple", "McNasty", or a foul smelling/tasting conditioner.

There are no guarantees that any of these remedies will work. If you do find something that works, persistence and continued application will probably be needed to continue to deter the goats.

By Christie Ward, DVM and Julie Wilson, DVM, University of Minnesota

The information given is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Minnesota Extension is implied.

How can I stop my mare acting up when in heat?

Q: My mare acts up when she is in heat. We aren't planning on breeding her so we are considering having her spayed. What are our options?

A: You do have a few options. However, it is important to make sure the ovaries are the cause of the behavior problem. Medical treatment involves adjusting her hormones so she doesn't come into heat. The most commonly used drug is progesterone (Regumate®). Inserting an intrauterine marble is also a non-surgical option, but should be discussed with your veterinarian.

Surgical treatment generally involves removing the ovaries and leaving the uterus. The University of Minnesota recommends a standing ovariectomy using the laparoscope and an instrument that melts the blood vessels shut. The laparoscope is the key tool for minimally invasive (keyhole) surgery and allows rapid healing with minimal complications. It also lets the surgeon see the ovary and its blood vessels.

Other options for removing ovaries include flank or vaginal incisions, without the laparoscope. These methods have additional risks, including hemorrhage and problems associated with the incision.

By Micky Trent, DVM, University of Minnesota

Can I treat my manure pile with anything to reduce flies?

Q: Can I treat my manure pile with anything to help reduce the amount of flies at my barn?

A: Your manure pile may be producing flies, depending on temperature, moisture content, and how long before it is spread. However, flies are likely to be coming from other sources, and spraying the manure pile alone may not produce the desired results. Breeding sites can be located by searching your premise for places where maggots are actively developing, including soiled bedding, feed debris, areas around waterers, etc. Once located, sources can be eliminated by scraping and spreading the manure, and by preventing manure accumulations from recurring.

If stall "pickings" must be piled, then consider composting as an alternative to spraying. For maggot control, you will need to create a hot, actively composting pile, where temperatures are greater than 140° F. Fresh manure will need to be mixed with another source of carbon, such as straw or sawdust. If space permits, create a new pile each week, and turn all piles weekly to maintain aerobic conditions.

By Roger Moon, PhD, University of Minnesota

Should I keep my horses on pasture in the winter?

Q: Is it recommended to keep horses on pasture once the ground has frozen and there is snow cover?

A: We do not recommend keeping horses on pasture over winter. There is minimal nutritional value in the dormant/dead grass and legumes. Hoof traffic and continuous grazing can cause considerable damage, which can results in weak plants or bare spots in the pasture the following spring and summer. Also, some poisonous plant skeletons, like white snakeroot, can remain above the snowline, tempting horses to ingest them. During winter months, keep horses in a safe area where they are fed hay, have water and shelter. As a guideline, turn horses back into the pasture the following spring after the pasture dries out and grasses and forages are between 6 - 8" tall.

By Krishona Martinson, PhD, University of Minnesota

What is osteoarthritis?

Q: What is osteoarthritis?

A: Osteoarthritis, also known as degenerative joint disease (DJD), is a degenerative process affecting the cartilage of a joint. The cartilage breakdown is caused by a variety of factors; age, injury, or over-use. Addressing possible underlying causes like removing chips (cartilage covered bone fragments) from the joint or addressing conformational problems is the first step in the treatment of DJD.

Because DJD is a degenerative process, the damage that has occurred to the cartilage cannot be reversed, so treatment relies on therapies designed to reduce inflammation and pain, and normalize the joint environment as best as possible. These medications include both systemic and local forms. Systemic joint medication can be administered orally, intravenously or intramuscularly, while local medications are injected into the affected joint directly.

By Florien Jenner, DVM, University of Minnesota

Can brewers yeast improve digestion and foot health?

Q: I have a question about brewers yeast for horses. Can it help the digestive system, hoof health, and improve fiber digestion?

Yeast appears to have an important role in the microbial digestion process, but the precise mode of action has not been identified. Yeast also appears to improve feed palatability, which helps horses maintain a more consistent feed intake. Therefore, yeast may help overcome the negative effects of less palatable feeds.

Feeding yeast to horses falls into 2 categories: dead and alive. Dead: brewer's yeast is one of the by-products derived from brewing. In the dry form, the brewer's yeast contains a relatively high concentration of high quality protein, and is also a good source of fat, water-soluble B vitamins (exception is B12) and the mineral phosphorus. It is sometime fed to horses in poor condition at the rate of 30 - 50 g/day, but is usually too expensive to feed regularly.

Live: yeast cultures of live yeast organisms are also used as a probiotics - live organisms that are fed daily and potentially have a positive role in the microorganism populations in the hind-gut. The most common strains of yeast fed as probiotics are Saccharomyces cerevisiae, Aspergillus oryzae and Torulopsis.

Based primarily on work with ruminants (cattle), live yeast cultures have been shown to synthesize a wide variety of enzymes that are able to break down fiber and proteins. Researchers have tested over 50 strains of S. cerevisiae and found only seven strains with the ability to stimulate growth of fiber-digesting bacteria. Consequently, these yeast cultures can aide in the digestion of forages, and to a limited extent, proteins and carbohydrates in grains (limited because most of the digestion of cereal grains occurs in the foregut of the horse).

The effectiveness of probiotics in horses of various ages is somewhat questionable. Investigations have shown that the effect of time since manufacturing, temperature variations, and acidity in foregut can all have an impact on viability of probiotics microorganism. Many of the probiotics available have been isolated and cultured from species different from the horse, and therefore may not be compatible with the equine gastrointestinal tract environment.

There have been a few studies which indicate that feeding live yeast cultures to young growing horses may have some benefit, with no advantage for the mature, healthy horse.

Horses with some conditions do seem to benefit, but without further studies, these products fall into the "can't hurt, may help" category.

By Hathaway, PhD & Valberg, DVM, University of Minnesota

How can nutrition affect hoof health?

Q: How can nutrition affect hoof health?

A: Maintaining your horse's nutrition can help alleviate some hoof problems. Feeding good quality hay, supplementing vitamins and trace mineral, and making sure your horse has constant access to fresh, clean water is important for hoof health and overall horse health.

Poor nutrition can lead to future hoof problems, and correcting a horse's nutrition can gradually improve hoof health over time. Cooperation between horse owners, veterinarians, and equine nutritionists are needed to ensure proper horse nutrition.

Research has shown that horses with poor quality hooves can benefit from commercially available hoof care products that contain Biotin (20 mg/day), Iodine (1 mg/day), Methionine (2500 mg/day) and Zinc (175 to 250 mg/day).

By Mary Boyce, DVM, University of Minnesota

Is nitrate poisoning a concern with horses?

Q: Is nitrate poisoning a concern with horses?

A: If nitrite is absorbed in blood in sufficient quantities it may convert hemoglobin to methemoglobin. Methemoglobin does not release oxygen to tissues, and can interfere with the animal's ability to use oxygen. Nitrates are normally found in forages, however, some forages can accumulate large concentrations of nitrates during dry or drought conditions. Ruminate animals like cattle and sheep are reported to be about 10 times more susceptible to nitrate poisoning than horses because their rumen converts nitrate to nitrite. The same reaction may take place in the cecum (hindgut) of horses to a lesser extent. Thus horses are generally tolerant of higher concentrations of nitrate in forage than cattle are.

The symptoms of nitrate poisoning in horses include: difficulty breathing, bluish-colored mucous membranes, weakness, tremors, and possibly death. Research has shown that feeding hay containing 1.5 to 2% nitrate to pregnant and non-pregnant mares resulted in clinically normal animals, even though higher than normal levels of nitrate were detected in blood samples.

As a general rule, most horses should not be fed hay containing more than 1.5% nitrate. DHIA (320-352-2028), Dairyland (320-240-1737) and the Minnesota Veterinary Diagnostic laboratory (612-625-8787) can test hay for nitrate concentrations. If forage contains between 1.5 to 2% nitrate, it should not be fed without diluting the forage with other feedstuffs (i.e., forages/grains lower in nitrate). If the forage is over 2% nitrate, it should not be fed at all. Nitrate exposure has also been associated with goiter (or hypothyroidism) because of the potential for nitrate to interfere with iodine. Offering iodized salt is the most practical prevention for goiter.

By Mike Murphy, DVM, University of Minnesota

What is the difference between FDA-approved joint supplements and nutraceuticals?

Q: What is the difference between a Food and Drug Administration (FDA) approved joint supplement and a nutraceutical type joint supplement?

A: Intra-articular, intravenous and intramuscular administered joint medications are considered to be drugs and are subject to FDA approval. All of these drugs have been tested by independent research and have been shown to be effective. Oral joint supplements (also known as nutraceuticals), however, are not considered to be drugs and are not regulated by the FDA. Because these products are not regulated by the FDA the amount of active ingredient claimed on the label is not necessarily what is contained in the bottle, and great variation can also exist in the purity and the absorbability (ability of the product to be absorbed in its active form after being given orally) of the product. Only few nutraceuticals have been tested scientifically, which makes it difficult for veterinarians to make recommendations for all but a few oral supplements.

By Florien Jenner DVM, University of Minnesota

Does hydrated lime control flies?

Q:Where can I get hydrated lime? I'm trying to do everything I can for fly prevention and putting lime in stalls and in wet areas was recommended to me.

A: Hydrated lime, calcium hydroxide, (commonly sold as barn line - any coop or farm supply store should have it), increases pH. It can help reduce ammonia odor in barn stalls. It will also help absorb moisture, which may help reduce flies.

At amounts commonly applied (usually minimal amounts), it is unlikely to provide benefit for fly control. Maggots are pretty tolerant of wide ranges in pH.

If you are using lime in a pasture area, significant use of the lime may increase the pH enough to inhibit plant growth. Bottom line, lime does not directly control flies.

By Roger Moon, PhD, University of Minnesota

Why is my horse sweating and shaking?

Q: My quarterhorse has had a problem with founder and laminitis. His front left coffin bone has stabilized. He also has a thyroid problem, but current medication has that stabilized. My question is, when we do trail ride, which is mainly walking, but some light trotting up hills, he breaks out in severe sweats with little or no riding. When we stop, his front section will go into slight tremors or leg shakes. I am wondering if I should have further testing done, or if this is normal considering his past issues.

A: How old is your horse? Older horses with founder should be considered as potentially having Cushing's disease. These horses will not shed out well, may drink/urinate more, and can have what we used to consider a low thyroid appearance. The disease makes them more prone to repeat founder episodes but can be controlled with medication. These horses do tend to sweat more, too. Have you tried him on pain meds to see if he still shakes? He may not be handling the trail ride well and it is becoming too painful or too tiring. If it is pain related, he should be better on a test dose of bute (discuss extended use with your vet). If the bute helps, he needs further testing to see if the pain is from his foot or someplace else in his leg. Continuing to ride him on the bute can put him at risk for further injury until you know why he is painful.

If the bute doesn't help, he may not be able to handle the work due to his condition. In this case, a good overall exam may help determine his muscle condition and strength. Cushing's horses tend to lose muscle tone. Muscle biopsies can help diagnose underlying problems and should be considered in younger horses. Electrolyte abnormalities in the blood could also cause the shakes but he would likely be a low risk candidate for this. Finally, if his foot is the issue, there are surgeries to help realign the bone in the hoof to make it less painful for him. We do think that the malalignment leads to stress and pain.

By Erin Malone, DVM, University of Minnesota

Can I use iodine for dipping a foal's navel stump?

Q: In last month's newsletter, you recommended Nolvasan® for dipping the foal's navel stump. What about iodine?

A: The Nolvasan® solution used at the U of M Veterinary Medical Center (VMC) contains 2% chlorhexidine, so 3 parts water must be mixed with 1 part Nolvasan® prior to use as an umbilical dip. Nolvasan Teat Dip Concentrate® may also be used; since it contains 4% chlorhexidine, 7 parts water must be added to 1 part Teat Dip prior to use.

As compared to dips containing povidone-iodine or tincture of iodine, 0.5% chlorhexidine kills more bacteria on the umbilical stump. Its effects persist for a longer period of time, and it is less likely to provoke skin irritation. Some foals develop severe skin scalding and even sloughing in response to iodine dips, especially when very strong products are used (e.g. 7-10%). These products can also dry the stump out too quickly, causing premature breakage and a higher incidence of patent urachus (a condition in which urine leaks from the navel stump).

At VMC, we believe that 0.5% chlorhexidine offers the best balance between disinfection and avoidance of tissue injury. Iodine solutions are still considered good disinfectants, but at low concentrations (e.g. 2% tincture of iodine or 1% povidone-iodine solution) they fail to kill some important bacteria, and at high concentrations (e.g. 7% tincture of iodine) they can cause chemical burns to delicate foal skin. When iodine is used, attention must be paid to the product's concentration.

By Christie Ward, DVM, University of Minnesota

The information given is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Minnesota Extension is implied.

What is the relationship between grazing on pasture and laminitis?

Q: What is the relationship between grazing on pasture and laminitis?

A: One of the factors that can predispose horses to laminitis is the rapid intake of nonstructural carbohydrates (sugars and starches). Intake of starches or fructans (a sugar) stored in pasture can cause laminitis. Fructans are the primary reserve carbohydrate stored in cool season grasses like fescue and bluegrass. Grazing management is important for horses predisposed to laminitis (often ponies and overweight horses). This includes limiting grazing during the times of day when fructans are at their highest level a in grasses.

Generally, horses predisposed to laminitis should graze in the evening and over night and be inside or in dry lots during daylight hours. Grazing should also be limited during times of environmental stress on plants such as drought or cool temperatures. Rotational grazing is recommended where regrowth is limited to 4 to 6". It is important not to over graze pastures as the lowest stems often contain the highest amount of sugar. Avoid grazing on pastures with lots of seed heads as they also contain high amounts of sugar.

By Stephanie Valberg, DVM, PhD, University of Minnesota

Does the University of Minnesota take donated horses?

Q: Does the U of MN take donated horses for research or education?

A: The University of Minnesota Vet School will take donations (alive or deceased) if funds are available, or if the horse is needed/suited for a research project.

For example, mares are occasionally accepted for use in the reproductive herd. However, the UMN Vet School is often asked to take donated sick or deceased horses. The Vet School is more likely to take a sick horse if the owners are willing to pay the $250 it costs to euthanize and dispose of the body, otherwise the Vet School has limited dollars to spend on donations. Horses slated to be euthanized are routinely kept alive for approximately 24 hours after a donation (if possible), and euthanized horses are often used for teaching purposes and are always treated with respect.

Please keep in mind that only a limited number of deceased horses are needed for teaching purposes and unfortunately, the U of M Vet School can not accommodate all owners wishing to donate their unwanted, sick, or deceased horse. Owners wishing to donate a horse can call 612-625-6700 for more information.

By Erin Malone, DVM, University of Minnesota

What if my broodmare can't provide colostrum for her newborn foal?

Q: What options do I have if my broodmare is unable to provide colostrum for her newborn foal?

A: A broodmare may be unable to provide colostrum for a variety of reasons, such as premature leakage, fescue toxicity, sudden death or mastitis. If the broodmare owner can anticipate this need, the best option is to find equine colostrum from a donor mare or farm, and administer it to the newborn foal in the first 2 hours of life. Ideally colostrum feeding should continue for at least the first 48 hours.

Colostrum contains concentrated antibodies against important infectious diseases. Good quality colostrum is thick, yellow to gray in color, and very sticky. Colostrum can be collected from either healthy mares that bear a stillborn foal, or from healthy mares that have an abundance, and can be frozen in ice cube trays and stored for future need. This is a common practice, and carries only a slight risk of complications. The U of M offer the National Colostrum network that maintains a list of horse owners willing to give or sell colostrum to other horse owners in need. This 24 hour hotline can be reached at 651-647-8391.

If a horse owner is unable to locate equine colostrum, 2 other alternatives are equine plasma given orally or intravenously, or bovine colostrum. Equine plasma has some of the same benefits as equine colostrum, but must be given in the first 12 hours of life. Bovine colostrum offers good protection against some of the intestinal diseases that affect both calves and foals, but may cause mild destruction of red blood cells. Lastly, if economic constraints do not allow for these interventions, every effort should be made to keep the foal as clean and dry as possible. The foal will be very vulnerable to infectious diseases until its immune system matures sufficiently to make its own antibodies.

By Julie Wilson, DVM, University of Minnesota

How can I protect my horse from ticks?

Q: How can I protect my horse from ticks?

A: Given horse skin can be quite sensitive, it is best to stay ON LABEL! There are some oral pastes like ivermectin and moxidectin, which will produce blood titers high enough to kill feeding ticks. Pour- or spray-ons for horses are more difficult to recommend. If one were worried about ticks on horses, keep them out of areas where ticks will be abundant. Such areas include densely vegetated (tall grass, shrubby ground) habitats. Dry paddocks and grazed pastures inside fences should not be a problem. Before riding into such areas, dose legs with a permethrin-based product (again, only if formulated for use on horses), which will repel ticks before they get attached.

Roger Moon, PhD, University of Minnesota

What is certified hay and where must it be used?

Q: What is certified hay and where must it be used?

A: The certified noxious weed seed free forage program is designated to assure that certified forage meets the minimum standards designed to limit the spread of noxious weeds. In Minnesota, there are no areas where certified forage (hay) must be used. When trail riding and camping in public parks, it is considered voluntary to use certified hay.

However, if you are planning a trail ride or camping trip with your horse to Wyoming, Idaho, Kansas, Montana, South Dakota, North Dakota, Nebraska, Utah or Colorado to ride on public lands, then certified hay must be used. The penalty for using non-certified hay ranges from $68 to $1,370, and the offender could also be responsible for the recovery costs to wildlife habitat.

For a current list of producers of certified noxious weed seed free forage in Minnesota, please call the Minnesota Crop Improvement Association at 800-510-6242.

By Krishona Martinson, PhD, University of Minnesota

If I think my horse is colicking, should I immediately call the vet?

Q: If I think my horse is colicking, should I immediately call the vet?

A: When a horse is in pain from colic, he will often look at his side and bite or kick at his flank or belly. More severe cases will lie down and/or roll, and in some cases, manure production will be decreased or absent. Often horses will improve when walked. If you know the colic is of recent onset and appears mild, you can try walking the horse and see if he improves without veterinary assistance. If it the duration of colic is unknown, or if the colic is more severe and unresponsive to walking, a veterinarian should examine the horse as soon as possible.

Owners can learn to take pulses and to check the horse's gums for signs of dehydration or toxicity. If the horse's heart rate is over 45-50 beats per minute or if the gums are tacky, have a prolonged refill time or are off color, the horse may be dehydrated or toxic and needs immediate attention.

By Erin Malone, DVM, University of Minnesota

What can I use in my fogger to control flies in my horse barn?

Q: What can I use in my fogger to control flies in my horse barn? I have tempo and seven on hand.

A: First, check to see if there are screens on barn entryways (i.e., windows and doors). If so, then try to keep horses inside when flies and mosquitoes are most active. Avoidance is always a good strategy, provided indoors is not the source of flies, especially stable flies.

Remember, fogging indoors will be temporary at best, and futile if flies can get inside from outdoor sources. Second, make sure manure is properly disposed on, including both indoor and outdoor disposal of feces, urine-soaked bedding, and any feed source wet enough to support fly breeding. A dry environment is good, and will limit on-site production of biting stable flies and nuisance house flies.

Hand-held misters or foggers are really designed to create a fog of a short-lived, contact insecticide such as the botanicals pyrethrins. Little droplets hit the flies directly, and they are killed as the toxin enters their bodies and disrupts their nervous systems. Pyrethrins are likely to be formulated with various synergists to enhance efficacy, and both are quite safe around animals, pets, and people. Pyrethrins are common and should be available from local tack shops or farm supply outlet. Seek products formulated for indoor use, and FOLLOW ALL INSTRUCTIONS on the container.

Tempo is one of the synthetic pyrethroids, and is meant to provide a longer acting (1-2 weeks) surface residue. Comparable products with other pyrethroids are also available. These can be applied as coarse water sprays to building and stall surfaces using a hand sprayer. Check the label to confirm, but I do not think Tempo is formulated for application with a hand mister/fogger. Sevin (carbaryl) is an organophosphate that is formulated for garden use, and I would be surprised if it is registered for premise applications against flies. Again, check the label to confirm.

Remember, the best way to reduce fly population is with cleanliness.

By Roger Moon, PhD, University of Minnesota

The information given is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Minnesota Extension is implied.

Should I be concerned about hoary alyssum?

Q: Should I be concerned about the weed hoary alyssum?

A: Hoary alyssum is mostly a concern in hay, as horses will not choose to eat it in pastures if adequate forage exist. When ingested, horses experience depression and a "stocking up," or swelling of the lower legs, 12 to 24 hours following ingestion. A fever and occasionally short term diarrhea have also been observed. These clinical signs normally subside 2 to 4 days following removal of the hoary alyssum source.

In more severe cases, an apparent founder with a stiffness of joints and reluctance of the animal to move has been observed, recovery of animals with these signs may take several additional days. In very rare cases, where hoary alyssum comprised 30 to 70% of the hay, circumstantial evidence exists associating the plant with the death of a few horses, however, death has not occurred in horses fed hay containing hoary alyssum under experimental conditions. In field cases, only half of the animals ingesting hay containing more than 30% hoary alyssum demonstrated any signs of toxicity. The cases of severe "stocking up," apparent founder, and death have only been observed in horses ingesting hay containing more than 30% hoary alyssum. Usually, only mild "stocking up" has been observed in horses on pasture or those ingesting hay with less than 30% hoary alyssum.

Bottom line: hay containing 30% or more of hoary alyssum, or any weed for that matter, should not be fed to horses. If you think your horse is suffering from hoary alyssum toxicity, contact your vet, as these clinical signs can be produced by many other diseases, including strangles.

By Krishona Martinson, PhD, University of Minnesota

Do I need to test my horse for Equine Infection Anemia (EIA)?

Q: I've recently heard that a Coggins test is not necessary. I'd also like some current facts on Equine Infection Anemia (EIA) and its risk to my horses.

A: First of all, a Coggins test, named after the virologist who developed the test, Leroy Coggins, tests for EIA. Many labs are now using a simpler ELISA test for EIA. EIA, also known as Swamp Fever, must be federally reported. There is no treatment, or vaccine. That is why there are laws requiring testing for public exhibition or interstate transportation. The virus is like HIV in humans, but is primarily transmitted by biting flies.

The best way to limit the spread of EIA is through annual testing of all horses, and immediate testing of any horse that shows signs compatible with the disease (fever, blood spots on mucous membranes, swelling of limbs, anemia). Horses with acute EIA have very high levels of virus in its blood, enough that one teaspoon has enough virus to infect thousands of horses. The asymptomatic (showing no signs) horse has much lower levels of virus in their blood, but still poses a risk to nearby horses.

The number of positive horses in Minnesota, by county, is available at the Minnesota Board of Animal Health website. The majority of these cases were identified by routine testing. In Minnesota in 2005, 5 horses tested positive out of 47,118 samples. Minnesota has had several years in the last ten where the positive cases were in the double digits. Several states, such as Arkansas and Texas, have had very active campaigns to reduce EIA cases. These testing programs have been successful in reducing the numbers of EIA cases and need to be continued.

Testing for EIA IS NECESSARY (via a Coggins test) to track and help contain the disease. It is recommended that all horses be tested annually for EIA. Testing is mandatory for horses being transported across state lines and attending certain shows or group events.

By Julie Wilson, DVM, University of Minnesota

Does hay give horses colic?

Q: Does hay give horses colic?

A: Hay diets (horses should receive at least 2/3 of their nutrition from forage, i.e., hay or pasture) tend to lower the risk of colic (horse on pasture pose the lowest risk). Good quality hay (free of dust, mold, weeds, and other foreign matter) should not give horses colic.

However, quickly changing hay types or qualities (i.e. changing quickly from a grass hay to an alfalfa hay) can induce colic, along with hay that is weedy, dusty or moldy. Several things can induce colic in horses, but quality hay is not usually one of them.

By Martinson, PhD, & Malone, DVM, University of Minnesota

How can I remove ice from my horse paddocks?

Q: I'm having trouble with ice in my horse paddocks. How can I remove the ice?

A: Ice is a problem in horse paddocks as falls and slips can lead to serious injury. The best solution is to remove the horse from the paddock, until the ice melts, but few horse owners have that option. Sand can be helpful to increase traction. However, it is ideal to not feed the horses in the area where the sand is spread to minimize the risk of ingestion.

Straight salt can speed the melting of the ice if temperatures are not too cold. There is no research documenting the effect of salt on horse hooves, but pure salt should be used in moderation as a precaution. If using pure salt to melt ice, make sure the horses have an alternative source of salt to reduce ingestion off the ground. A mixture of sand and salt should not be used in horse paddocks due to the chance of horses accidentally ingesting the sand via their interest in the salt.

Other options like shavings, hay, and straw tend to slide over ice and do not provide additional traction. Small rocks can provide traction, but can be accidentally ingested or become lodged in hooves. To reduce water/ice in the future, improve the grade, install gutters on the barn, and reduce the amount of manure in the paddock.

By Malone & Wilson, DVMs, University of Minnesota

Why is one of my horses chubby and the other one thin?

Q: This summer, we have two horses supported on 6 acres of grass pastures. One is an easy keeper and continues to be chubby. The other has always been an easy keeper, (ridden 5-6 times a week) but is quite thin now. Shouldn't the other horse be thin as well? We have no bare spots in our pasture, but the pasture is grazed down. Is there a way to know how much pasture is needed per horse beyond the vague 2 acres per horse guideline?

A: It is very difficult to measure the amount of grass a horse is actually eating on pasture. On average, good pasture produces about 3 tons of grazeable dry matter (DM) per acre per year (June - September) or about 50 pounds a day per acre. A horse needs to eat about 2% of its body weight to maintain a healthy body condition (about 20 pounds a day for a 1,000 pound horse). Each day, each horse should be eating about 40 pounds of grass. We recommend 2 acres per horse because the pasture grasses need about 30 days of rest (no grazing) for every 7 to 10 days of grazing (this will vary depending on time of year and weather conditions). Is your 6 acre pasture divided up to provide a rest period for a section of the pasture, while another section is being grazed (i.e. rotational grazing)? When the pasture is eaten down or over grazed, the amount of grass available is very minimal or zero.

I'd recommend getting an exam on the "thin" horse to ensure its teeth are in good chewing condition and that there are no underlying health problems contributing to the weight loss. Riding 5 to 6 times a week is considered more than "recreational", and your horse's energy requirement is beyond the base 2% figure. Are you providing vitamins and minerals as well?

Even though your pasture looks green, it's highly unlikely there is enough available grass if its "eaten down" to support both horses.

It's very common for individual horses to respond differently to grazing in regards to weight loss and gain. Some horses in the same pasture will consume more grass than others. It would not be surprising or uncommon to have one thin and one over weight horse in the same pasture.

We recommend horse owners with horses on pasture monitor their horse's body condition score on a weekly basis, both to monitor weight gain and loss. If a horse is gaining weight, restrict the amount of time allowed to graze. If a horse is losing weight, supplement hay or grain. Monitoring body condition score is one way to estimate the amount of grass a horse is actually ingesting when on pasture.

By Krishona Martinson, PhD & Paul Peterson, PhD, University of Minnesota

What is a good mix of alfalfa and timothy?

Q: It's nearly time to seed our hay field into horse hay after having it in corn last season. Can you tell me what would be a nice mix of alfalfa and timothy? Also, do you know what rate to seed oats as a nurse crop to keep down weeds? I do prefer alfalfa in my horse hay, but not clover.

A: I like your plan of seeding an alfalfa-grass mixture under an oat nurse crop. However, there may be better grass options than timothy in that mix. What kind of soil do you have? That might influence the best grass option(s). I trust the field has adequate pH (upper 6.0's), potassium levels, and drainage to support good alfalfa production?

For the oats, if you're on sandier soil, no more than 1 bushel (bu)/acre (ac). If you're on heavier, more clayey soil, you can probably go as high as 1.5 bu/ac. If you're planning to harvest the oat for grain, use no more than 1 bu/ac no matter what the soil type.

Regarding the grass species in the field, a number of different options can work well. Timothy is often favored by horse owners, but it lacks the total season production that other grasses have. It generally provides a nice first cutting, but not much after that. This would be even more pronounced on a more droughty soil, so 2nd and 3rd cuttings would be mostly alfalfa.

Smooth bromegrass has some of the same problems with yield distribution as timothy. Orchardgrass generally has better yield distribution, drought tolerance, and total season yield than timothy or brome. Same is true for reed canarygrass. If you use orchardgrass, its probably best to request a relatively late-maturing variety for better hay quality potential and better persistence. If you use reed canarygrass, ensure its a low-alkaloid variety. For a hay mix that you'd like close to 50:50, I'd recommend 7-10 pounds (lb)/ac of alfalfa. Orchardgrass or reed canarygrass seeded as the sole grass could be seeded at 4-6 lb/ac. Bromegrass has a larger seed, so that would be seeded at 7-10 lb/ac. Timothy seeds are small, so 3-4 lb/ac is usually adequate.

If you choose to use some combination of grasses, you can decrease their rates proportionally. The ranges provide flexibility for what species you'd like more dominant, if any.

Designing hay mixtures is science-based, but there's certainly some art and personal preference involved as well! As a side note, most horses do not need the amount of protein that is usually found in alfalfa dominate hay. The excess protein exits the body via the urine and can lead to strong ammonia smells. Finally, clover, generally speaking, is more difficult to dry in hay compared to alfalfa.

By Paul Peterson, PhD, University of Minnesota

When should I begin grazing my horse this spring?

Spring turn-out (grazing initiation) should be determined by: stocking rate (how many horses/total pasture acreage), pasture species and condition, ability and availability of mowing/haying equipment for paddocks that may get too mature for effective pasturing, and species height and maturity.

On average, 2 acres of well-managed pasture can provide the forage needs for one horse from spring to fall. "Well managed" means subdivided into multiple paddocks, fertilizing according to soil tests, and controlling weeds. If you have that much or more acreage per horse, you may want to start grazing early to get a jump on the spring pasture growth. If you have less than 2 acres per horse, the pasture cannot be expected to meet all the forage needs for your horses during the grazing season. In this case, plan to provide some hay and designate a sacrifice area/paddock to feed horses as needed to allow adequate rest (on average 2 weeks in spring and 6 weeks in summers) for the pasture.

Grass pastures with good stands of Kentucky bluegrass or smooth bromegrass can handle early spring grazing. "Early" means when bluegrass is 3-4" tall and bromegrass is about 6" inches tall. These grasses are sod-forming and tolerant of horse hoof damage. Pastures dominated by bunchy-growing grasses like orchardgrass and timothy should be taller, about 10" in height. These grasses are more easily damaged by hoof action and grazing. If conditions are really wet, it's best to wait, regardless of plant height. Introducing horses to spring pasture gradually will reduce the chance of laminitis. Slowly begin grazing (15 minute grazing periods at first), working your way up to a full day over a couple of weeks.

By Paul Peterson, PhD, University of Minnesota

Does reed canarygrass work well in wet pasture areas?

Q: I have areas of my pasture that remain quite wet for an extended period of time after it rains. Would reed canarygrass work well in these types of areas?

A: Reed canarygrass is one of the best species for poorly drained soils and tolerates flooding better than other cool season grasses. Reed canarygrass seed tends to be more expensive and more difficult to establish than other grass species, but is suited for the situation described. Reed canarygrass can also be invasive, but newer varieties tend to be less invasive. This means it might be difficult to remove reed canarygrass from your pastures once it's established or to keep it from invading native wetlands. Be sure to keep horses out of the wet areas until the area has dried. If the horses are allowed to graze when wet, it can result in soil compaction, destruction of plant material, hoof problems, and other potential injuries.

By Krishona Martinson, PhD, University of Minnesota

Do I need to vaccinate show horses and colts for Equine Herpes Virus?

Q: My vet suggested that we vaccinate the show horses and the colts for equine Herpes virus infections, as he is concerned about the neurological form of the disease. I thought only broodmares needed to be vaccinated for this.

A: Many people share your interest in the protection provided by vaccination for equine Herpes virus infections, which can be highly contagious. Horses are most often affected by two types: Equine Herpes Virus 1 (EHV1) and Equine Herpes Virus 4 (EHV4).

EHV4 causes upper respiratory disease with cold-like signs in horses, frequently spreading through a stable or herd. In contrast, EHV1 infection is associated with broodmare abortions in the second half of pregnancy or the birth of weak foals that seldom survive without very intensive treatment.

In the past, most veterinarians routinely recommended vaccination against EHV1 to reduce the risk of herpes abortion in broodmares, and EHV4 vaccination to prevent respiratory disease. There is some cross protection between EHV1 and EHV4 vaccines, and stronger immunity may occur from the modified live vaccines (Rhinomune and Calvenza). None of the vaccines were believed to protect the horse from the neurologic signs associated with EHV1. However, a new study conducted at Cornell University has challenged this belief. Using the strain of EHV1 that caused an outbreak of neurologic disease in multiple horses in Ohio, the researcher was able to show that prior vaccination with the modified live product, Rhinomune, actually prevented development of the neurologic disease in the majority of the animals when ponies were experimentally exposed to this strain. This vaccine, although originally designed to protect horses from EHV4, also has been shown to offer protection from abortion induced by EHV1 when administered quarterly.

For owners of multiple broodmares, this alleviates the headache of timing vaccination specifically at 5, 7 and 9 months of gestation, as recommended for the killed EHV1 vaccine, Pneumabort K. The quarterly recommendation is made for high risk broodmares only. Most veterinarians vaccinate other horses annually or semi-annually. Until more data is available, it is premature to recommend that all horses get the extra vaccinations.

By Julie Wilson, DVM, University of Minnesota

How do I reseed compacted areas of my pasture?

Q: The soils in my horse pasture have a very high level of clay. Areas that my horses use a lot get very compacted. If I want to reseed a compacted area what steps would I take so the grass will grow?

A: Compacted soil resists absorption of water, restricts movement of air around the roots, and produces a physical barrier to the development of roots. Research from Montana State University suggests soils were not compacted by horse hooves when horses were grazed for short periods of time. Longer term changes in soil compaction may result from repeated or continuous grazing. If you are experiencing compaction from horses, it should only be surface compaction and if your pasture if getting sufficient rest, the compaction should be minimal.

On average, pasture areas need 30 days of rest between grazing periods of approximately 7 days. The rest period allows the pasture to rest and regrow. The rest period can also be beneficial to horse owners. It allows time to mow, fertilize (if needed), drag and chemically control weeds (if necessary).

If resting the pasture area doesn't seem to help, aerification should. Aerification relieves soil compaction and increases water and oxygen infiltration into the soil. Aerification is best done in the cooler weather of late summer (August 15 to September 15). Aerification is done with an aerifier. An aerifier is a machine which removes plugs of soil, leaving holes about a half-inch in diameter and up to 3 inches deep. The cores of soil are typically left on the soil surface to gradually break down and filter back into the grass. If you have a large pasture, aerification might not be practical. An aerifier can be rented or hired through a lawn service.

When trying to establish a pasture in a compacted area, first take a soils test. Fertilize the area as needed, aerate, then drag your seed (or use a slit seeder) into the ground. If severe compaction is observed, tillage (such as plowing or disking) may be needed. Remember that unless you change your practices (like giving the pasture rest), compaction will continue to occur.

By Krishona Martinson, PhD, University of Minnesota

With limited hay supply in my area, is it safe to feed baleage to my horses?

You can feed baleage to horses, however, there are some precautions you need to take. Horses are very susceptible to botulism, which is linked to baleage and is often fatal. Horse owners who are feeding baleage should consider vaccinating their horses with at least two initial immunizations against this disease and then continue with yearly boosters. However, the vaccine is rather crude and causes considerable vaccination reactions in some horses so it is not a decision to make lightly. As baleage feeding is uncommon, most veterinarians are unlikely to have the vaccine in stock so they will most likely need time to order it.

If hay is short, consider feeding alfalfa cubes, beet pulp or increasing the horse's grain. However, remember that horses need their diet to consist of at least 2/3 forages in some form or another.

By Julia H. Wilson, DVM

Is it safe to fog my barn for flies if my hay is stored inside the barn?

There are many kinds of insecticides on the market that can be applied as space sprays inside closed barns. Most available products for this use contain active ingredients that are botanical pyrethrums or pyrethroids. These chemicals kill the adult flies that are exposed directly to the spray. In general, these chemicals can be used safely inside horse barns, because they are relatively non-toxic to animals and people, and their active ingredients break down rapidly. Some product labels state clearly that application to animals or their feeds should be avoided, while others are less restrictive. Whichever material you choose, you should read the package label carefully and follow its instructions. Look for statements about how to apply the material, and for statements that would restrict the kinds of places where the product can be used safely. You should avoid direct application to feeds and animals, unless the labels state otherwise.

Benefits of fogging closed barns are likely to be temporary. Time required for fly numbers to return will depend on how much fly breeding is occurring inside the barn, and how well the barn is screened to exclude flies from outside.

By Roger Moon, PhD, University of Minnesota

How warm should my water be during winter to help ensure my horses drink enough?

To maximize water intake, water temperature should be between 45 and 65° F. To help maintain water temperature, it is a good idea to house the water source inside a barn or lean-to if possible. If the water source needs to be outside, make sure the water source is protected from the wind and freezing rain and/or snow.

By Krishona Martinson, University of Minnesota

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