Maintaining optimum equine health is the number one priority of horse owners and feeding plays a crucial role in achieving this. Below are descriptions of some of the most common conditions horses in New Zealand are susceptible too, and tips on how to prevent them through nutrition.

Digestive Conditions

Among the various conditions and diseases that can affect the equine digestive tract, the most common ones are gastric ulcers and hindgut acidosis. These were also covered in an earlier Lifestyle Block article here.

                Gastric Ulcers

Gastric ulcers can occur in all horses, however, they are most common in racing and performance horses. The most common type of ulcer is squamous ulcers, which occur through prolonged exposure of the upper squamous mucosa to gastric acid. Glandular ulcers in the lower part of the stomach can also occur through a breakdown of the mucous layer due to a consistent acidic environment and exposure of the glandular layer to acid. Ulcers can also occur in the pyloric region, which is the lower bend where the stomach curves to join the duodenum. Due to their location, these are often the trickiest to treat.

Prevention of ulcers involves providing adequate amounts of long-stemmed fibre through pasture and/or hay, and avoiding leaving a horse without food for more than four hours. Lucerne provides significant buffering properties against gastric acid and providing a handful of lucerne before work can help to reduce acid splash to the squamous region. It is also important to keep grain meals small, and in horses with severe ulcers, grain should be replaced with more fibre through ingredients such as beet pulp and soy hulls (eg. McMillan Grain Free) and digestible fat sources such as cold-pressed canola oil or KER Equi-Jewel high fat stabilised rice bran conditioning supplement.

Treatment of ulcers is best discussed with a veterinarian and involves a course of omeprazole, the active ingredient that inhibits the production of gastric acid and allows the ulcers to heal. Continued management can be achieved through using credible, research-backed supplements such as Maxia Complete or Maxia Digest from Seahorse Supplements.

                Hindgut Acidosis

Similar to ulcers, the disruption of hindgut microbes and decrease in pH known as hindgut acidosis can also occur through inadequate forage intake, as well as high grain feeding. The equine caecum and colon are home to billions of microbes with the main role of fermenting fibre, which provides energy and various by-products such as B vitamins. The main cause of hindgut acidosis is undigested starch from grains and sugars from pasture entering the caecum and colon, disrupting the delicate balance of microbes that reside there, and causing acidic conditions.

Prevention through nutrition involves providing adequate forage through at least 1.5% of the horse’s body weight in pasture, hay and fiber products daily. Keeping grain meals to below 2.5kgs per meal, and feeding grains processed with heat and pressure such as pelletising and steam flaking also helps to ensure starch is digested in the foregut and avoids the overflow of undigested starch into the hindgut where problems can occur. Reducing the reliance on grain through using fibre and fat sources can significantly improve the condition, and McMillan Grain Free or NRM Low GI Sport are ideal for this. KERx EquiShure hindgut balancer can also significantly improve hindgut balance and restore pH in affected horses.

Tying Up

Recurrent Exertional Rhabdomyolysis

Recurrent Exertional Rhabdomyolysis (RER) is an abnormality in muscle contraction brought about by excitement and exercise and thought to occur due to a problem with the way calcium is regulated inside the muscle cell. This condition primarily affects breeds that are characteristically hotter in temperament and leaner in body type such as Thoroughbreds, Standardbreds, Arabians and racing Quarter Horses. Symptoms include firm, painful loin and croup muscles at the beginning of, or during exercise, reluctance to move, muscle tremours, profuse sweating, rapid breathing and dark urine. Diagnosis is confirmed by a blood sample displaying high levels of muscle enzymes CK and AST.

As RER is significantly influenced by behaviour, management involves taking measures to reduce excitability and keep the horse calm. This could involve feeding and working them first, and always ensuring they are around other horses they are familiar with. Reducing starch and sugar in the horse’s diet and utilising alternative energy sources such as fibre and fat is also highly recommended, and McMillan Muscle Relieve is ideal in this situation. Adequate salt and electrolytes are also important for working horses, and additional antioxidants such as natural vitamin E are also highly beneficial.

Polysaccharide Storage Myopathy

Polysaccharide Storage Myopathy (PSSM), also known as Equine Polysaccharide Storage Myopathy (EPSM), Azoturia, or ‘Monday Morning Disease’ is common to the heavier, and often quieter breeds such as Quarter Horses and Warmbloods. PSSM is caused by an accumulation of glycogen in skeletal muscles and occurs when glucose is pulled from the bloodstream and deposited into the muscle tissue more quickly than normal, possibly due to insulin sensitivity of muscle tissue. Type 1 PSSM horses have a mutation in a gene (GYS1) which appears to cause the unregulated synthesis of glycogen. Type 2 PSSM horses have abnormal glycogen storage however do not possess the GYS1 mutation. Diagnosis is confirmed by muscle biopsy or genetic testing for the type GYS1 mutation. Symptoms include muscle firmness and pain, cramping, twitching and stiffness, sweating, stretching as if to urinate, intolerance to exercise, poor performance and related behavioural changes, muscle weakness and atrophy and gait abnormalities.

PSSM is managed through maintaining optimum body weight by monitoring conditions carefully and providing the correct amount of daily energy. Dietary management is relatively strict and studies show a diet providing less than 10% of daily digestible energy as dietary starch and sugar and more than 13% of daily digestible energy as dietary fat is recommended. This means low-quality forage such as last season’s hay, which can be soaked for thirty minutes to decrease sugar content further, with feeds containing high-quality fat and digestible fibre as energy sources.  For good doer types, low-quality forage with NRM Equine Balancer is ideal. For working horses with higher calorie requirements, higher quality forage with feeds containing higher fat levels is recommended such as McMillan Grain Free, Muscle Relieve or NRM Low GI Sport.

Metabolic Conditions

Equine Metabolic Syndrome

Equine metabolic syndrome (EMS) is a term that refers to a group of conditions including obesity, insulin resistance, and a tendency toward laminitis. It is characterised by a high body condition score (5 on the 0 – 5 scale; 8-9 on the 1-9 scale) and particularly areas of visible subcutaneous fat and a cresty neck.

Management of the condition includes achieving an optimum body condition score through dietary management and exercise, provided the horse is sound and laminitis free. Pasture intake should be controlled by either restriction or the use of a grazing muzzle and providing low-calorie hay to meet forage requirements of 1% of the horse’s body weight daily. Hay testing can reveal accurate sugar levels and soaking hay is also highly effective at reducing sugar content. Balancer pellets such as NRM Equine Balancer are ideal for meeting nutrient requirements without contributing to the condition.


Laminitis is a painful and very serious condition that involves inflammation of the laminae in the hoof. There are multiple ways the disease can manifest, including injury and retained placenta, as well as through equine metabolic syndrome and insulin resistance. However one of the more common ways it occurs is through the consumption of storage sugars called fructans found in cool-season grasses, particularly in times of rapid growth such as spring.

Where most sugars and starches are easily digested in the horse’s small intestine, the strong bonds in fructans mean that they pass undigested into the cecum and colon, causing shifts in the microbial population, upsetting hindgut pH, and producing endotoxins which can cause laminitis. For particularly sensitive horses, even a small amount of fructan-rich grass can quickly trigger laminitis that can be highly debilitating if left untreated.

To avoid problems when turning horses out on spring pastures, introduce pasture access in small segments several times a day and gradually increase the number and length of these access periods. Continue to offer hay to horses turned out on fresh pasture to ensure they are consuming enough fibre, and monitor manure consistency and hoof temperature. Take the horse off pasture and call the veterinarian if the horse shows signs of hoof discomfort like reluctance to move, shifting from one foot to another, or assuming a leaning-back posture.

Cushings (PPID)

Equine pituitary pars intermedia dysfunction (PPID) or equine Cushing’s disease is caused by an enlargement of the pars intermedia of the pituitary gland, resulting in overproduction of the steroid cortisol and loss of the normal feedback mechanisms that affect cortisol production. Horses affected with PPID are often older, underweight, and may have insulin resistance with or without recurrent laminitis. Clinical signs of PPID include long hair that does not shed in summer, weight loss, laminitis, increased susceptibility to infections, and excessive water intake and urination.

Dietary recommendations for horses with PPID are dependent on body condition and the presence of insulin resistance, however in any case, a predominantly forage diet should be adopted that maintains ideal body condition. Being overweight increases the risk of laminitis, and calorie restriction through low-quality forage and a balancer pellet such as NRM Equine Balancer is required in this case. Textured or sweet feed containing greater than 3% molasses and 15-20% non-structural carbohydrates (NSC) should be avoided if there is evidence of insulin resistance. If the horse requires additional calories for weight gain, feeds containing >10% fibre and >5% fat such as McMillan Grain Free can be fed instead. Medical treatment of PPID such as the use of Pergolide should be discussed with your veterinarian.

For further assistance with the management of any equine conditions, consult a qualified Equine Nutritionist.

Article supplied by Luisa Wood, Equine Nutritionist.