16/ JUNE 2017 THE RIDER Investigating Poor Performance


Investigating Poor Performance Part 2


Dr. Bri Henderson BVMS MRCVS ACVSMR-resident Cheltenham Veterinary Centre Caledon, Ontario 905-838-3451 As we discussed in part 1 of our


“Investigating Poor Performance” se- ries, most often the root cause is an or- thopaedic or


lameness problem,


however, there are other causes which must be kept in mind. Nutrition plays a large role in the


energy and focus of an athlete. Many of our commercially prepared diets still contain molasses to improve palatability. The problem arises that if you have a horse which is undergoing a great deal of stress during competition/training, that small amount of molasses can be enough to tip them over the edge and contribute to stomach ulcers. Horses are the ultimate ‘fat adapted


athlete’. The years of relying solely on oats and grains as an energy source has taught us a great deal about colic and stomach ulcers. Carbohydrates are fer- mented in the hind gut of the horse which (1) produces a great deal of heat and (2) when carbohydrates are pro- vided in excess, causes pH shift and the death of ‘healthy bacteria/microbes’ cre- ating a more acidic and volatile GI en- vironment. The introduction of healthy fats


into the horses diet has allowed us to in- crease the energy density of the food we offer as well as reduce the stress on the gut. Studies report that fat should make up no more than 10-12% of the horses’ diet and focus should be given to choos- ing high quality fats (soya, flaxseed) avoiding fats which are less available to the horses’ system for energy (canola, corn). The added benefit of choosing a higher quality fat source is that these products are also higher in Omega Fatty Acids which have been proven to have antiinflammatory effects on the respira- tory tract, musculoskeletal system and skin.


Stomach ulcers occur in 50-90% of


sport horses depending on the popula- tions surveyed and the type of athletic activity (i.e. 80-90% racehorses, 70% endurance horses, 60% show horses). Colonic ulceration is estimated to


occur in 65% of sport horses Initial clues that your horse has an


ulcer issue may be somewhat vague - change in attitude, reduced performance, dull coat, weight/top line loss. As the severity of the ulceration increases, changes in blood work, faecal blood testing as well as more dramatic behav- ioural/physical changes are noted. Pre- disposing factors are similar for both stomach and colon ulcers with stress (environmental/transport), nutrition and NSAIDs being the biggest risk factors. Once a diagnosis is made, manage-


ment and treatment can begin. For stom- ach ulcers, a course of omeprazole along with dietary modification (minimizing sugar/molasses, free choice hay) and omega fatty acid supplementation are the mainstays. In comparison, healing hind gut ulcers often involves the reduc- tion of workload for the colon by reduc- ing hay consumption and supplementing roughage chunks or chopped hay (short fibres), in addition to medication support to heal the ulcerated areas and reduce the inflammation. Hindgut acidosis is a major contributor to colonic ulceration in our population of sport horses. Most often this is caused by a “spill over” of carbohydrate from the stomach/small in- testine that is rapidly fermented by the microbes of the hind gut. This rapid fer- mentation releases lactic acid which re-


duces the colon pH and alters the mi- crobe population as well as the healthy mucosa of the intestine. These horses often have frequent low grade colic is- sues that are never well explained. An- other form of colonic ulceration is “Right Dorsal Colitis” which develops during treatment with NSAIDs and can cause mildmoderate colic signs with no major findings on rectal examination. For either cause of colon ulcers, an


ultrasound examination of the horses’ abdomen is the best bet and defining the situation. Nutrition of the equine athlete can


be further complicated by the existence of a metabolic disease. Exertional Rhab- domyolysis, PSSM, Equine Metabolic Syndrome and Cushings are the four most commonly encountered metabolic issues within sport horses. Each requires its own specific management program to reduce the impact of the disease and allow the horses to reach their full po- tential. Muscle disorders Exertional


rhabdomyolysis or


“Tying up” can occur sporadically in horses of any breed, age or sex. Most of these cases are related to muscle trauma, overexertion/exhaustion, or diet/ elec- trolyte imbalances. In horses where there is a predisposition to tying up (Re- current Exertional Rhabdomyolysis, PSSM, Malignant Hyperthermia) there is an underlying dysfunction of the mus- cle cells that cause the condition. Recurrent Exertional Rhabdomyol-


ysis (RER) is found in 5-7% of Thor- oughbreds and Standardbreds (increased incidence in females versus males) world wide and is caused by an abnor- mality of the contraction/relaxation cycle within the muscle cell. There ap- pears to be a psychological component where these horses are more likely to have an attack after being excited or “held back” by their rider. Maintaining a calm environment with a consistent schedule and daily exercise are key to managing these horses. In addition, a diet that is high fat (low starch/carbohy- drate) with supplemented salt will help reduce the risk of an attack should the horse become excited or anxious during exercise. Massage/physiotherapy stretching and suppressing mare’s heat cycles have also been discussed as man- agement techniques. PSSM or Polysaccharide Storage


Myopathy comes in two types. Type 1 have an identified genetic mutation that causes the muscle cell


glucose/glycogen improperly within the muscle cell. Type 2 PSSM horses have all of the signs of PSSM without the ge- netic mutation. Type 1 PSSM is most common amongst the Quarter Horse, Paint and Appaloosa breeds


(6-8%) as well as


Belgians/Percheron (36-54%). Type 2 PSSM has been identified in several breeds from Quarter Horses, Paints, Ap- paloosa, Morgan Horses, Warmbloods, Thoroughbreds and Arabians. Management is similar to ER cases


in that high fat/low starch/carbohydrate concentrate with hay that has 12% or less of nonstructural carbohydrate (NSC) is key. Attaining the high fat diet can be done by supplementing fat sources (flax seed, soya, rice bran, fish oil) and/or choosing a commercial diet that has 10-12% fat and low NSCs. The second key factor in managing these horses is exercise. During an acute at- tack, horses should not be walked and the veterinarian should be called. How- ever, when managing horses to prevent attacks, consistent low level exercise is a must. This can be achieved through maximum turnout out but should also in- volve a daily exercise program of ‘long and low’ stretching to maintain fitness and help stabilize blood glucose:insulin


to store


levels. For any horse that has experi- enced “tying up” there is anecdotal evi- dence that supplementing vitamin E/Selenium may help to prevent episodes. Equine Metabolic Syndrome Equine Metabolic Syndrome or


“Insulin Resistance” is more commonly identified in young horses with abnor- mal fat pad formation, obesity and a his- tory of laminitis. Assessment of glucose:insulin ratio is a good starting point to confirm suspicions of EMS. Management of these horses includes a low NSC diet and encouraging weight loss. This includes preventing access to pasture (dirt paddock, muzzle) and en- suring that hay supplied is tested and low in sugar/ carbohydrate levels. Alter- natively, hay can be soaked to remove the carbohydrate prior to feeding. As- suming the horse is sound, instituting an exercise program will help shed extra pounds as well as improve insulin sen- sitivity. Cushings/PPID While this is typically a disease


found in older horses (mid teens to geri- atric), horses as young as 7 years old have been diagnosed. Clinical signs in- clude muscle wasting, difficulty regulat- ing body temperature, lethargy, poor performance, susceptible to infections, altered/poor skin quality. Cushing’s is caused by a benign tumour of the pitu- itary gland. This causes a hormonal im- balance which leads of an excess of cortisol (stress hormone). Cushings can be controlled with a medication called Pergolide (Trade name: Prascend) and additional supplements of amino acids and Omega Fatty Acids can help im- prove skin quality and muscle tone. Hypothyroidism Primary hypothyroidism is ex-


tremely rare in horses. Any alteration in thyroid hormones is typically a result of another disease (like Cushings or EMS). While supplementing thyroid hormone to increase metabolic rate and help with weight loss in obese horses is a reason- able option, it should never be the only treatment used. Identification of the pri- mary problem and appropriate medica- tion and management will be key to gaining the greatest success. Respiratory Disease When discussing upper airway is-


sues, our primary concern is the free flow of air in and out of the lungs. Any- thing that might increase the effort with which air is inspired or expired can cause poor performance. The use of ‘overground endoscopy’ (a video-endo- scope that the horse wears during exer- cise so we can see how his pharynx changes at work) enables us to recognize a whole host of dynamic upper airway obstructions that are happening when the horses’ head carriage is positioned abnormally (i.e. Dressage, hackney driv- ing pony). Pharyngeal collapse is one of the


most difficult abnormalities to manage and is often caused by compression and


significant flexion of the head and neck. We believe that the compression of soft tissues impacts the nerves ability to fire appropriately and allows the soft tissue of the pharynx to be “sucked in” by the inspiratory pressure. These horses will often get out of breath easily and strug- gle to work as hard as their fitness level suggests. In severe cases, there may also be a sense of panic which coincides with a collapse of the walls of the pharynx.


Endoscopy images demonstrating pha- ryngeal collapse. Notice that the walls of the pharynx are billowing inwards causing a dramatic narrowing of the pharynx and tracheal opening. (Franklin, Equine Veterinary Education,February 2017)


Laryngeal Hemiplagia or “roaring”


is also a common cause of upper airway dysfunction. The arytenoid cartilages are the


gate keepers of the trachea - opening and closing with inspiration and swallowing respectively. The job of the arytenoid cartilages is to “close” and protect food/water from going down the trachea and then to open wide with inspiration to make the entrance to the trachea as large as possible (imagine breathing in through a little straw versus a big straw - its easier with the big straw). When the nerve that controls the muscle to these cartilages is damaged, the muscle weak- ens (or atrophies) and allows the carti- lage to fall down into the tracheal opening. In addition to a dramatic reduc- tion is size of the opening, tissue which was once pulled tight is now relaxed and able to reverberate as air passes by. The reduction in size of the tracheal opening is what causes the poor performance, while the noise is caused by the loose tissue reverberating as air passes by it. Surgical correction is the most success- ful treatment. A “tie-back” surgery in- volves securing the affected cartilage in a permanently “open” position which re- stores the tracheal opening to its normal size. The second surgical procedure in- volves removal of the tissue to prevent noise on inspiration. A comparison of normal upper air-


way anatomy and laryngeal hemiplegia (“roaring”). Lower airway disease is a common


cause of performance issues amongst sport horses. Inflammatory airway disease is


thought to occur in up to 50% of young horses. Signs can be a subtle as the oc- casional cough at the start of work or some mild mucous discharge from the nasal passages. These horses are normal at rest and with appropriate management changes can completely recover. It is


of sterile saline is pushed down the tube into the bronchus and then sucked back out - effectively “washing” the lung. This enables us to make microscope slides of the lung wash and determine what cells are present and if any fungus or bacteria are found. Dusty bedding, mouldy hay or arena dust can all be con- tributing factors to lower airway inflam- mation. While some horses will require a period of medication to help settle the inflammation, management changes are the keystone to success and preventing the inflammation from becoming chronic. Dust free bedding, good quality


hay, avoiding the use of round bales (or feeding them in nibble nets to limit horses “disappearing” their head into the middle of a bale) and maximizing turnout are key elements of the manage- ment changes necessary. Recent litera- ture has supported the use of Omega Fatty Acids (flax seed oil, soya oil, fish oil) to reduce airway inflammation. Commercial supplements exist for pur- chase (Equine Omega Complete) or the addition of flax seed can be incorporated into a horses feeding regime (1lb of ground flax seed per day). Recurrent Airway Obstruction


(Heaves) is a chronic inflammation of the airways which occurs in older horses. Narrowing of the airways (bron- choconstriction), mucus production and bronchospasm are the hallmarks of this disease and these horses are not normal at rest. Often treatment with steroids and bronchodilators is necessary to maintain comfort for these horses. However, medical treatment alone


will only bandaid the issue. Caution with hay quality (low/no dust or


Continued on page 17


important to remember that the changes within the lungs will begin long before any outward signs are noticeable. A thorough physical exam (before


and after exercise) and ultrasound of the thorax is a good starting point to diag- nosing IAD. The gold standard to deter- mining the severity and clues to the cause is a “Broncho-alveolar Lavage” (BAL). A tube is passed down the horses trachea and into the main bronchus where a small balloon is inflated to hold it in place. At this point a small volume


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52