Managing The Horse With Cushing’s

The vet has diagnosed it and the reality begins to sink in – your horse has Cushing’s disease. Now what?  Cushing’s is an endocrine disease caused by a tumor on the pituitary gland that is most often seen in older horses and ponies. This tumor results in high cortisol and is most often exhibited by  hyperglycemia (high glucose), excessive thirst, excessive eating, excess urination and a shaggy haircoat.  At this time there is no cure for Cushing’s but by keeping a close eye on nutrition and management, we can improve the quality and possibly lengthen the life span of a Cushing’s horse.

Routine is important to the Cushing’s horse because changes in diet, medication, etc. can have negative effects on health.  Cushing’s horses have a compromised immune system and for that reason, seemingly small or mundane parts of their care become very important.  There are a few management practices that are particularly important: 

  • Deworming – Cushing’s horses can be more susceptible to parasites because of their weakened immune system.  Work closely with your vet to develop a deworming schedule and program that is catered to your horse. Your vet should also be seen regularly for dental care and wellness exams.
  • Farrier Care- Regular farrier visits are important because certain types of leg and foot conditions are more likely with a Cushing’s horse, such as abcesses of the hoof and laminitis. Signs of laminitis can be a tender footed stance and the horse acting like he is “walking on egg shells”. 
  • Grooming – Hair coat and temperature regulation are problems in Cushing’s horses so you will want to help your horse as much as you can by preventative grooming practices. Consider body clipping in hot/humid weather and be mindful of temperature and weather changes. When blanketing, make sure the hair coat is dry and clean to help reduce the incidence of skin issues. Prompt treatment of any wounds or infections is essential.
  • Feeding- One of the main goals in feeding the Cushing’s horse is to control the starch + sugar (NSC) content per meal. This helps to regulate the blood glucose and insulin levels.  The NSC content of the concentrates fed to the horse is important, but even more so is the content of the hay /forage and the combination of the two together. Some guidelines have suggested an NSC maximum value of 10-13% based on the total diet (forage + concentrate). Testing your hay will give you a good idea of the NSC values.
  • Consider a feed that is fortified with lysine, methionine, biotin, vitamin E and complexed trace minerals (copper, zinc, manganese and selenium) to help maintain muscle mass, support hoof growth and support the immune system.

Following these tips will help improve the quality and possibly length of life for the horse diagnosed with Cushing’s.  If you have specific questions regarding your horse, please work with a qualified nutrition consultant or your veterinarian.

Feeding “George”: A Polysaccharide Storage Myopathy (PSSM) Horse

Previously, I introduced you to George, my ‘Heinz-57’ PSSM positive horse.  Though his test results came back positive for Type 1 PSSM, his diagnosis does not mean his athletic career is over. With some diligence and routine, George is able to lead a normal life as a successful working partner.

One key to managing his condition is maintaining consistency in his diet and routine. Remember, he would get sore every time the hay changed, particularly if it had alfalfa in it.  First I work to ensure that George’s total diet is properly balanced which starts with controlling the starch and sugar energy sources in his hay and grain ration.  I buy larger quantities of grass hay (no alfalfa) that will last awhile, a full year if possible. I also have my hay tested before buying it to make sure it isn’t too high in non-structural carbohydrates (12% NSC or less), and that the rest of the nutrients are within an acceptable range for good quality hay, as this is the bulk of his diet. The lower the NSC in the hay, the more room there is in the diet to add calories from fat. More on that below.

To balance his hay, he gets a controlled starch feed concentrate that is fortified with essential amino acids, complexed trace minerals, pre- and probiotics.  If I need to add calories to his diet to support higher levels of exertion during training and show season, I add a balanced fat supplement to the concentrate component of his diet.  To meet the total caloric requirement it is recommended that PSSM positive horses receive no more than 10% of the digestible energy from non-structural carbohydrates (starch and sugar), and 15-20% of the digestible energy should be supplied by fat.  Remember, this applies to the total diet, contributions from grain plus forage.  Working with a qualified equine nutritionist is a great way to figure all of this out.  In a nutshell, I control the sugars and starches in his total diet (low NSC grass hay and low calorie, controlled NSC grain) and add a nutritionally balanced fat source when extra calories are needed. The only supplement he gets is vitamin E, which helps boost his antioxidant status (helps fight oxidative stress), and supports muscle recovery after exercise.  Because his total diet is balanced for selenium, I don’t supplement this mineral to avoid potential toxicity.

Estimating his weight and doing a regular body condition score help me adjust his diet and exercise routine accordingly, so he maintains good muscle mass and avoids excess fat deposits.  In addition, I make sure to minimize stress as much as possible by keeping his routine consistent.  His daily ration is divided up into 3 meals to avoid one large grain meal and he has access to hay for most of the day.  He gets a minimum turnout of 8 hours every day with a buddy and limited access to fresh forage.  I also exercise him at least 6 days a week.  With this management routine, regular veterinary and farrier care, he has never “tied-up” on me, and continues to excel in dressage with the occasional hunter pace thrown into the mix. Providing good quality of life is a top priority, especially when it comes to managing even the most challenging horses, and I think George would agree, he is doing great!

Meet “George”: A Polysaccharide Storage Myopathy (PSSM) Horse

I’m proud to introduce you to George, a “Heinz-57” draft cross, and my current equine partner.  He is the result of a ½ Thoroughbred, ½ Percheron (dam) x ½ Hanoverian, ½ Paint horse (sire). I’ve had the privilege of knowing George since he was a weanling, and bought him as a yearling.  It wasn’t until I started him under-saddle as a three and a half year old that I started noticing behavioral changes (crankiness – not like George), non-specific muscle soreness, and a transient, almost undetectable gait abnormality, all of which happened to be associated with new hay delivery.  I won’t mention how much I’ve spent having him worked-up, imaged, adjusted, fitted and many more things to get to the bottom of what his body was trying to tell me.  We were coming up empty handed and frustrated.

It wasn’t until after I returned from an equine nutrition symposia that it occurred to me to have him tested for polysaccharide storage myopathy (PSSM). PSSM causes the horse’s muscle cells to store energy (glycogen) in excess, which can result in a variety of symptoms, the most severe of which is tying up after aerobic exercise.  Nearly all of the classic signs were there, short of a bad tying up episode.  Wouldn’t you know it, he came back positive for Type-1 PSSM a.k.a. EPSM, tying- up syndrome/exertional rhabdomyolysis/Monday morning disease, set fast or azoturia.  There is more than one version of PSSM (Type-1 is most common) and the diagnostic tests for each are unique.

Recent advances in equine genetics have made testing a blood, muscle, or hair follicle sample possible.  As it turns out, three of the four breeds that George represents have been identified as prone to carrying the genetic mutation responsible for PSSM.  Unlike some other recessive genetic diseases, PSSM is inherited as a dominant gene; in other words having just one copy of the mutated gene means the horse has the disease.  Horses lucky enough to inherit 2 copies of the gene can be more severely affected.   The good news is, with a little diligence, these horses can be managed and go on to have a good quality of life and successful athletic careers; both of which I want for George. 

Diagnostic information can be found at the University of Minnesota Neuromuscular Diagnostic lab website: http://www.cvm.umn.edu/umec/lab/home.html

Prevention and Management of EMS in Horses

There is no treatment or cure for Equine Metabolic Syndrome (EMS), so taking preventative measures though diet and exercise are the best defenses against the development of EMS.

Crinkles on Toby's neck are evidence of his 'overweight' status

Here are some great defensive strategies to help prevent your horse from developing EMS:

    • Prevent obesity by providing a forage-based nutritionally balanced diet with controlled starches and sugars.
    • Maintain an optimal body condition through regular exercise.
    • Work with an equine nutritionist or veterinarian to understand what a healthy weight and body condition is for your horse to help prevent over-feeding or dietary imbalances that can contribute to EMS.

For horses who already are dealing with EMS, follow these tips to help successfully manage their condition:

    • Prevent or reduce obesity through controlled starch and sugar in the total diet along with exercise (unless horse is painful from laminitis episodes).
    • It is recommended that these horses have very little to no access to fresh pasture to avoid the overexposure to the sugars in grass.  Use of grazing muzzles or a dry lot are good alternatives to stall confinement, as this allows the horse to exercise on its own.
    • Have a nutrient analysis done on your hay to understand the NSC content – keeping in mind that it is important to understanding to NSC content of the total diet (hay + grain, if applicable).
    • Soaking hay (15 – 30 min warm water) can help leach out some of the sugars in the hay, just be sure to feed the hay right away before it spoils, and discard the sugar waste water, so the horse does not have access to it.
    • Low calorie ration balancers are good horse feed options to balance the diet if there are vitamin and mineral deficiencies from feeding a forage only diet, and/or from soaking hay.

 

 

What is Equine Metabolic Syndrome (EMS)?

EMS is an endocrine (hormonal) disorder in horses, similar to metabolic syndrome in humans, that is characterized by obesity, insulin resistance, and regional adiposity (abnormal fat deposits), which can predispose affected horses to chronic  laminitis.

What types of horses are affected? 

First and foremost, most horses do not suffer from EMS.  Most horses tolerate dietary carbohydrates (e.g. NSC, starch, sugar, fructan) quite well, and thrive on this important and readily available source of energy.   Performance horses in particular need sufficient NSC in their diets for work and recovery after exercise.  Too little starch and sugar in the diet can actually diminish athletic performance over time in non-EMS horses.

Tess the pony indulges

That being said, EMS can occur in any breed, however ponies, Morgans, Paso Finos, and horses that tend to be “easy keepers” seem to be most vulnerable to developing EMS.  It should also be noted that not all obese (fat) horses are insulin resistant, and not all insulin resistant horses are fat.

How do I know if my horse is insulin resistant (IR)?

Veterinary diagnostic testing (blood work) is recommended to confirm IR, but here are some other classic signs of insulin resistance in horses and ponies:

  • A classic sign of IR is a “cresty neck”, of which a clear correlation between neck circumference and IR has been documented.
  • Horses with regional deposits of lumpy or dimpled fat pads (e.g. behind the shoulder, around tailhead, over the loin), are suspect of being IR.
  • Horses that seem to gain weight rapidly, or blow up easily, particularly in spring with new pasture growth, relative to other horses may indicate IR.
  • Horses that are tender footed, and/or that demonstrate rings on the hoof wall, expanded white line and blood spots on the soles of their feet,  suggests mild, chronic bouts of laminitis and IR.

EMS is easily confused with other clinical disease such as Cushing’s Disease (a.k.a. pituitary pars intermedia dysfunction) and hypothyroidism due to similar clinical signs, despite different underlying causes.  It is very important to work with a trusted vet to ensure an accurate diagnosis if any of these conditions are suspected.

A word of caution, single blood samples for the diagnosis of IR can be very unreliable and misleading as several factors unrelated to EMS influence glucose and insulin levels (time and content of horse’s last meal, type of feed horse is adapted to, time of day sample is collected, stress level of horse), leading to false conclusions.  Taking multiple blood samples over several days, or utilizing techniques such as the euglycemic insulin clamp or a combined glucose insulin tolerance test (CGIT) are more involved, but can lend more validity to the lab analysis.  In any case, early detection of EMS and other endocrine disorders is preferable.

B-Vitamins in Horse Diets

Water soluble vitamins, which are the b-vitamins such a niacin, thiamine, folic acid, and many others, are excreted from the body on a daily basis in the urine.  B-complex vitamins play an important part in allowing horses to metabolize the nutrients contained in feedstuffs, by facilitating carbohydrate, fat and protein utilization within body cells, providing the energy needed for growth, performance and reproduction. All of the B-complex vitamins are essential to horses, but they are synthesized by bacteria in the cecum and colon. After microbes form the vitamins, they are absorbed through the intestinal wall and are available for use by the horse’s body cells. Bacteria in healthy adult horses generally produce adequate levels of the B-complex vitamins.

Since bacteria in the horse’s digestive tract produce B vitamins, several factors influence the B vitamin status of horses. Changes that affect the bacterial population may change the synthesis and availability of B vitamins, and they include, but are not limited to:

• Drugs, which selectively kill certain species

• Horses going “off feed” thus reducing the availability of food for the bacteria

• Dietary changes which change the levels of fiber, carbohydrate and protein passing to the bacteria in the hindgut

In addition, situations that decrease the horse’s ability to absorb B vitamins have an effect on overall vitamin status include:

• Chronic or clinical diseases that interfere with efficient metabolism by the horse

• Parasitism, through ulceration of the mucosa and direct competition for vitamins in the feed, causes reduce availability

• Diarrhea bouts reduce B vitamins for the horse

• Moldy feed, especially hay contaminated by Streptomyces, makes biotin unavailable for horses

• Stress tends to decrease the horse’s ability to absorb B vitamins

• Anti-metabolites present in plants such as bracken fern, yellow star thistle or horsetail, interfere with thiamin utilization and transport

Finally, information on the B vitamin requirements and synthesis in young, growing horses and performance horses is limited. While there is much anecdotal evidence available about the effects of supplementing b-vitamins to horses, few actual research studies have been completed to determine the actual results of such supplementation, positive or negative.