Hay Soaking: All Washed Up or Good Management?

This article is courtesy of Krishona Martinson, PhD, University of Minnesota.
Posted on Nutrena’s Blog

Soaking hay in water is a common strategy used to manage the nutrition of some diseased horses.  Current hay soaking recommendations include soaking hay for 30 minutes in warm or 60 minutes in cold water for removal of carbohydrates (Watts, 2003).  Soaking hay is commonly done to manage horse diagnosed with laminitis, Polysaccaride Storage Myopathy (PSSM), hyperkalemic periodic paralysis (HYPP), and chronic obstructive pulmonary disease (COPD).

  • Researchers have suggested that diets contain less than 12 and 10% nonstructural carbohydrates (NSC) for horses affected with laminitis (Frank, 2009) and PSSM (Borgia et al., 2009), respectively.
  • Reynolds et al. (1997) determined that a diet less than 1% K is necessary for horses diagnosed with HYPP.
  • Moore-Colyer (1996) determined that soaking hay for 30 minutes reduced respiratory problems for horses diagnosed with COPD or heaves.

However, how efficient is hay soaking, and are additional essential nutrients lost during the soaking process?  Researchers at the University of Minnesota set out to determine the impact of water temperature and soaking duration on removal of NSC, crude protein (CP), minerals, and dry matter (DM) from alfalfa and orchardgrass hays.

Four hay types were soaked, including bud and flowering alfalfa, and vegetative and flowering orchardgrass.  Individual flakes were submerged for 15, 30 and 60 minutes in 25 liters of cold (72°F) and warm (102°F) water, and for 12 hours in cold water.  A control (non-soaked) sample was also evaluated.  Water temperatures were determined by using the cold or warm only faucets, similar to practices implemented by horse owners and managers.  Subsamples of entire flakes were submitted for nutrient analysis at a commercial laboratory.

  • Prior to soaking, both alfalfa hays were below the 10 and 12% NSC threshold for horses diagnosed with PSSM and laminitis, respectively, and would not have required soaking. The orchardgrass hays were above these thresholds, however, after soaking for 15 to 30 minutes were at or below 10 to 12% NSC.
    • Although soaking hay for longer durations did further reduce NSC content, it is not recommended.  All horses, even diseased ones, require carbohydrates in their diet.
    • The severely limited NSC content in hay soaked for greater than 1 hour, combined with increased fiber amounts (fiber components are not water soluble, thus they are concentrated in soaked hay), brings into question the palatability and availability of nutrients in hay soaked for longer periods of time.
  • Crude protein leaching was variable in soaked hays, something other researchers have also observed (Moore-Colyer, 1996).  More importantly, previous research looked at the nutrient availability and quality of rained-on hay fed to steers and suggested the nitrogen remaining in rained-on hay is more stable, water-insoluble (Rotz and Muck, 1994), and possibly less digestible by ruminants (Licitra et al, 1996).  Additional research is needed to evaluate this concept when feeding soaked hay to horses.
  • Calcium (Ca) is not as prone to leaching during soaking compared to other minerals, and appears to be dependent on hay maturity.  As soaking duration increased, leaching of Ca increased in alfalfa bud and vegetative orchardgrass hays (immature hays).  However, soaking had no effect on Ca leaching in the more mature hays.
    • Conversely, magnesium (Mg) Mg and phosphorus (P) levels were reduced in all hay types as a result of soaking, with longer soaking durations leading to greater reductions.  Because Ca is not as water soluble as P, high Ca:P ratios were observed in hays soaked for  longer durations, specifically after 12 hours.
    • Ideally, Ca:P ratios should range from 1:1 to 3:1 (up to 6:1) in horse diets (NRC, 2007).  The high Ca:P ratios observed after longer soaking durations were exaggerated in alfalfa hays which had higher Ca:P ratios prior to soaking.
    • After 12 hours of soaking, a deficiency in P was observed and ranged from a shortage of 1 to 8 grams for a 500 kg horse in light work (NRC, 2007), and Krook and Maylin [32] suggested that osteochondrosis may be associated with excess dietary Ca.
  • Soaking both alfalfa and orchardgrass hay for 12 hours was necessary to sufficiently reduce K concentration to recommend levels prior to feeding horses diagnosed with HYPP (Reynolds et al, 1997).  Although K levels can be reduced by soaking, neither alfalfa nor orchardgrass hay is an appropriate option for horses diagnosed with HYPP due to the naturally high levels of K.

Owners should rely on forage analysis as the primary method of determining the appropriate hay for horses, especially when feeding horses diagnosed with laminitis, PSSM, HYPP or COPD.   Hay soaking for short durations (15 to 30 minutes in duration) is an acceptable management method, but should only be used if ideal hay is not available.  Hay should not soak hay for greater than 1 hour.  Soaking hay for long durations resulted in severely reduced NSC content, high Ca:P ratios, shortage of P in the diet and significant losses in DM.



By: Katie Jones, CVT

The Streptococcus equi bacterial disease causes horse owners to cringe and barn owners to become nervous. “Strangles” is the term used to describe this condition seen in infected horses when the lymph nodes around the throat become large enough to suffocate the horse. It typically occurs in horses 1 to 5 years old.

Causes: Exposure via direct contact with an infected horse or contaminated objects.

Incubation period: 3-14 days

StranglesClinical Signs:

  • First sign of infection is a fever ranging between 103°F-106°F.
  • 24-48 hours after the fever spike: nasal discharge, depression, inspiratory respiratory noise, and difficulty swallowing.
  • The horse may keep their head down and neck stretched out.
  • The lymph nodes become swollen and painful due to the formation of abscesses.

Diagnosis: Confirmed by a bacterial culture collected with a nasal swab.

strangles1Treatment: Under a veterinarian’s direction.

  • Hot compressions to swollen lymph nodes to encourage drainage. If they don’t drain on their own, they may need to be lanced and flushed.
  • Suspected infected horses need to be isolated from others.
  • If the lymph nodes are swollen to the point the horse is struggling to eat, they should be fed a soft diet.
  • Penicillin is an effective drug for treatment. Occasionally, if Penicillin is started before enlarged lymph nodes are seen, the disease process could stop.


  • The abscesses can rupture and drain through the skin, into the throat and nasal passages, or into the guttural pouch. Each of these conditions has different treatment options and complications.
  • The future development of “Bastard Strangles”.
    • Caused by: The infection spreading into the blood stream; thus, traveling to all the lymph nodes of the organs (liver, kidney, intestines, heart, spleen, and brain).
    • Clinical signs: Weight loss, episodes of colic, and a general decline of health.
    • Requires intensive veterinary management to recover.

Prevention: Strict hygiene protocol (quarantine)

  • A barn with a positive case should have everything disinfected which COULD HAVE come into contact with the horse (stall walls, buckets, ect.).
  • Traffic in and out of infected facilities needs to be restricted.
  • Available Vaccine. The immunity from both the vaccine and natural exposure is short lived. This vaccine is recommended if the horse is at a boarding facility or travels to shows throughout the year.
  • Three negative nasal swabs should be obtained before allowing an infected horse to re-enter a herd.

Strangles 2

Long Term Effect: Most horses which become infected will shed the bacteria for approximately a month after recovery.

The Chronic Coughing Horse

Dr. Kevin Voller

TLung pic2he chronic coughing horse is the topic of today. Coughing can originate from either the upper respiratory tract or the lower respiratory tract. The upper respiratory tract refers to the nasal passage ways, larynx (throat) or the trachea. The lower respiratory tract refers to the lung itself. Coughing comes about from irritation of the lining of the airways or the lung itself having inflammation or increased fluid accumulation in the airways or the lung. Most, but not all, upper respiratory issues relate to some type of infectious process, such as viral or bacterial infections.   These can involve inflammation or infection of the tissues lining the upper respiratory tract or structures of the airways such as the guttural pouches or sinuses that can retain fluid. The contagious causes of a cough are the infectious viral and bacterial agents such as influenza, rhinopneumonitis, rhinitis, equine viral arteritis and streptococcus equi. These infectious agents can cause issues in the lower respiratory tract from the primary infection. Problems also arise after the infection has resolved, yet the inflammation induced in the lung has not been eliminated. The non-infectious primary causes of a cough include lung worm, exercise induced pulmonary hemorrhage, inflammatory airway disease, and recurrent airway obstructive disease. Other causes such as neoplasia, summer pasture – associated obstructive pulmonary disease will not be discussed here.

Below is a diagram of the respiratory tract of the horse. For our purposes we will define the upper respiratory tract as beginning at the nostril and extending to where the trachea (windpipe) divides prior to entering the lungs; the lower tract is from this division all the way into the lungs. The analogy used to understand the lower respiratory tract would be a large oak tree. The oak tree has a trunk which rises from the ground before it divides into large branches, which extend further up and divide into smaller branches which extend further up, dividing into smaller branches before ultimately ending in the leaves. The trunk would equal the trachea, which divides into the major bronchi, which divide further into smaller bronchi which ultimate split into bronchioles which ultimately end in the alveoli (air sacs) – the alveoli being the leaves on the tree in our analogy. The alveoli are the site where the oxygen and carbon dioxide exchange take place.

Coughing may be the only symptom that is a concern for owners, but it is often not the only symptom. In some horses other symptoms may be present and would include increased respiratory rate, nasal discharge or, in some cases, nondescript poor performance or even exercise intolerance. In some cases, the problem may start just as a persistent cough, but over time progress to the other symptoms. As stated earlier, the goal of today’s discussion is only to touch on a couple of the causes of lower respiratory tract disease that cause chronic coughing.

Lungworms are a rare cause, but can have symptoms identical to some of the other alveolar picproblems. In my twenty plus years of practice I have only seen lungworms a couple of times. Lung worm life cycle is such that the adult develops in the bronchi and bronchioles of the airway. They lay eggs which are then coughed up, swallowed and then hatch in the intestine of the horse. The small worms called larvae are passed in the manure. These crawl out of the manure pile onto the grass. The larvae are then eaten by the horse that consumes the grass. Those larvae then migrate through the gut wall and are carried to the lungs through part of the circulatory system. The lung worms cause no obvious GI signs while migrating through the gut wall, but the adults and their larvae and eggs cause inflammation in the lung resulting in coughing, increased respiratory rate, and mucous in the lung. In almost all cases lung worm infection in the horse came from exposure to pastures that have contained infected donkeys or mules. The donkeys and mules typically show no symptoms of lungworm infection. Treatment with ivermectin or moxidectin typically resolves the parasitic infection.

Exercise induced pulmonary hemorrhage (EIPH) occurs when a horse exerts itself and bleeds within the lungs. Horsemen refer to this as a “bleeder”. This is a disease primarily of the race horse or the barrel racing horse, as it seems to occur only when the horse has to exert itself to this extent. Owners may see varying degrees of hemorrhage that come from the nostril, from marked to none. Some horses may cough following the bleeding, but others may only have poor performance, running a slower time, or start objecting to running. In some cases it has been the horse that becomes overly excited at a barrel competition. Bleeding does not typically occur during the training sessions. Diagnosis is made by seeing the blood externally, performing an endoscopic examination very shortly after a competition (within hours) or finding evidence of prior bleeding in the BAL sample. This can be found up to days afterwards. Some “bleeders” may have primarily inflammatory airway disease which may be successfully treated. If the inflammatory issue is eliminated, the “bleeder” status of the horse may resolve. The cause of EIPH is unknown at this time, and is an ongoing source of research. Treatment of EIPH involves preventing or moderating the bleeding by using Lasix (furosemide) prior to competition.

Inflammatory airway disease is a descriptive disease that is characterized by poor performance, exercise intolerance or coughing with or without excess mucous, and non-septic inflammation(NO infection present). This is a disease of the younger horse and the horse is not sick-meaning no fever, depression or inappetitence. It may originate from a viral infection that has resolved but the inflammation is still present. Poor air quality, barns with poor ventilation or chronic exposure to dust or molds or hay with the same may be an inciting cause. Some horses may have an allergic component that started or perpetuates the inflammation. Diagnosis is based on results of BAL cytology and culture from the lung or lower airway. Treatment depends on the cause. Anti-virals such as interferon or rest help resolve viral causes.   Corticosteriods are beneficial for inflammation reduction and may reduce the responsiveness to the dusts, molds or allergens. Anti-histamines are of benefit for cases caused by allergy. In most cases bronchodilators are not of help.

Reactive airway obstructive (RAO) disease is the new term for what previously has been referred to as chronic obstructive pulmonary disease (COPD). Horsemen have historically referred to this condition as “heaves”. So what is the difference, and why the name change? Because the medical term COPD refers to the human respiratory condition and the horse “COPD” is very different in cause, condition and treatment. In horses, there is spasm of the small airway in addition to increased mucous and purulent material (pus) development within the airway. So why? We are still not sure. There are, however, changes that occur within the tissues that make them over respond to various chemical stimulants (histamine) as well as to dusts and molds. Most horses with RAO/heaves are housed in a barn for some period of time, are exposed to dusty/moldy forage or on dry dusty lots or paddocks. The goal for treatment is to improve air quality.   This means trying to keep the horse out of doors, removing access to round bales or any dusty hay. Some horses may have to come off hay all together and be maintained on hay cubes or pellets. Various medications are used to treat the symptoms. These are typically based on corticosteriods, bronchodilators and, for some horses; the use of antihistamines may be beneficial. Another set of horses will require antibiotic treatment based BAL results, culture and sensitivity.

Lung pic

So how are the different conditions diagnosed? Your veterinarian will get a history; perform a physical examination including an auscultation of the respiratory and cardiovascular system. Blood work may be indicated based on the history and examination. What has helped the most in arriving at a diagnosis and treatment protocol has been the bronchoalveolar lavage (BAL). This is a “washing” of the lower airways of the horse with sterile fluid, recovering a portion of this fluid, performing a microscopic analysis and culture of this fluid. The procedure is performed at the clinic because processing of the sample is very time sensitive and requires immediate centrifugation and processing of the fluid. How is a BAL performed? The horse is lightly sedated to reduce coughing. A sterile tube that is similar in size to a stomach tube is passed up the nostril and down the trachea to the bronchi where it gently lodges. A cuff on the tube is inflated and sterile fluid is put down the tube and recovered. This fluid is then processed for analysis of the cells in the recovered sample. The types and percentage of the cells as well as presence or absence of bacteria in the cells determines the appropriate treatment. A sample for culture and antibiotic sensitivity are also submitted to determine if there is an infection as well as what antibiotic is appropriate for treatment.

When do you need to have a veterinarian out to examine a persistent cough? Most infectious respiratory conditions should resolve in 3- 4 weeks and frequently much more rapidly than this. The “sick” horse – meaning increased respiratory rate, elevated temperature, in appetence or depression – may require timely examination and treatment; consult with your veterinarian. If you have a horse that has a cough that is not resolving or a persistent cough that is developing I would suggest that you contact your veterinarian for a course of action. The course may involve management changes only, but if this does not resolve the issue further diagnostics and treatment may be required.

What is up my horse’s nose?

Bleeding from the nose is a relatively common clinical complaint and can be quite distressing for owners. If your horse has a nose bleed, it is best to keep the horse quiet and calm so that the bleeding will stop. In most instances, the bleeding will stop in 15-20 minutes.

When presented with a nose bleed, there are several questions that your veterinarian will ask. The first question is whether the bleeding is from one or both nostrils. Other questions we will ask are: Has this happened before? What were the circumstances that brought about the nose bleed? Was the horse exercising or at rest? Was there a traumatic incident? How much blood was there? Was it just a trickle or a gusher? These questions help us start to put the pieces of the puzzle together. However, the key piece of diagnostic equipment that we use to determine the source of the hemorrhage is a video endoscope. An endoscopic exam allows us to visualize the inside of the respiratory tract on a monitor. The image is produced through the scope that is introduced into the nasal passage and is then advanced to visualize the entire upper respiratory tract. There are many different causes and there are several different locations within the horse’s respiratory tract that can serve as the origin of a nose bleed. Most conditions that create hemorrhage from the nose are not life threatening; however, there is one condition that can result in death. This condition, called guttural pouch mycosis (a fungal infection in the guttural pouch) is fortunately not common.

Some causes of nose bleeds include: ethmoid hematomas, EIPH (exercise induced pulmonary hemorrhage), sinus problems, trauma, foreign bodies, infections and tumors.

Ethmoid turbinates are normal structures within the nasal passages that warm the air as it passes over them. They are highly vascular and therefore can easily bleed. This is the most common cause of nosebleeds after a horse has had a stomach tube placed because the tube can traumatize the turbinates as it is being passed.

Ethmoid hematomas are a tumor that consists of a mass of abnormal blood vessels that can grow on the ethmoids. This is not a life threatening condition but will often result in mild hemorrhage, as well as head tossing and exercise intolerance. In some cases, these masses can get quite large, occluding air flow through that nasal passage. Diagnosis is done by using an endoscope to visualize the nasal passage and upper respiratory tract. Treatment is usually a series of injections of dilute formalin to shrink the mass. In some cases a laser may be used to ablate the tumor.

EIPH is a common condition in race horses and to a lesser degree in barrel horses. It is hemorrhage that originates in the lungs, secondary to an intense maximal exertion. It is estimated that anywhere from 40-75% of race horses have EIPH. However, less than 10% of these horses actually have visible bleeding from their nostrils. Diagnosis is based on history of exercise-induced bleeding, cough, exercise intolerance or a decrease in the horse’s performance level. Hemorrhage in the trachea can be visualized 30-60 minutes post exercise with an endoscope. In many cases the horse cannot be scoped that soon after exercise and we will instead see an abnormal puddle of discolored fluid within the trachea when the horse is scoped. In some cases we will take a sample of fluid for analysis to help us come to a diagnosis. We also have a longer scope that will allow us to go into the horses lungs and look at these structures for blood. Once the diagnosis is made these horses will usually be prescribed a drug called Lasix (furesomide). This drug will be used pre-race to decrease the severity of the bleeding. A large percentage of racehorses are given Lasix pre-race after the horse has been confirmed as a “bleeder” by scoping.

The most serious condition that results in hemorrhage from the nostrils is called guttural pouch mycosis. This is a fungal infection that develops within the one of the guttural pouches. Horses have two guttural pouches which are extensions of their auditory tubes and have an opening into the back of their throat. There are several very important structures present within the pouches: several cranial nerves and the internal carotid artery. If the infection causes significant damage to this artery it can rupture. Endoscopic examination of the guttural pouch can diagnose the problem before life threatening events can occur. Treatment is an intensive daily infusion of anti-fungal medication into the pouch. This is a long treatment course as the fungal infection is difficult to resolve.

Uncommon miscellaneous conditions that can cause nose bleeds include foreign bodies, infections or tumors in the nasal passages or sinuses. Trauma to the head or face is the most common cause of nose bleeds these and will usually resolve within a short time. The bottom line for diagnosis of nose bleeds is the use of an endoscope to image the areas in question. As they say a picture is worth a thousand words.