How to Interpret Your Hay Test

ESC plus the more complex sugars present in the hay sample. The difference between WSC and ESC is essentially the complex storage sugar called fructan. Forage testing labs are not yet testing specifically for this sugar but it is possible to get an idea of the fructan content of your grass hay by subtracting the ESC value from the WSC value. The difference is the approximate percentage of the fructan in your hay sample. There is increasing evidence from ongoing research that fructan is a carbohydrate compound that may be causing significant health issues for our metabolically challenged horses.
Starch is a complex form of sugar that the plant may use to store carbohydrate. Most cool season grasses do not store plant carbohydrates as starch and so it isnt usually a very significant component of hay.
Nitrate is a nitrogen containing compound that can be toxic to horses if ingested in large enough amounts. Hay can become high in nitrate if it is irrigated by high nitrate water excessive applications of nitrogen containing fertilizers or if the hay field is infested with weeds that are high in nitrate. High nitrate can cause gastrointestinal irritation colic andor diarrhea in your horse but the biggest risk from nitrate is that of nitrite toxicity. 
Nitrate is converted to the more toxic nitrite in the hindgut of the horse by the fibre fermenting bacteria. Once converted the nitrite travels through the gut wall into the bloodstream where is interferes with the ability of the horses red blood cells to carry oxygen. Clinical signs of nitrite toxicity are laboured breathing or panting ataxia convulsions grey or bluish mucosa abortions in pregnant animals and death. Ensure that nitrate levels on your hay test are low or negligible.
Digestible Energy DE
Energy is frequently described as being a nutrient but in actual fact its a measure of the fuel provided to the horse by other nutrients. DE or digestible energy is a calculated value that is an attempt to quantify the amount of fuel provided by a feedstuff. On your lab report DE is a computer derived calculation that has taken into consideration all the nutrients contained in the hay. 
Digestible energy is quantified in terms of calories or in horse nutrition megacalories MCal and is a unit of measurement equal to one million calories. Calories are the units of energy that represent a standardized amount of heat released when organic
compounds undergo combustion in animals bodies.
إن مقارنة الأعلاف المخصصة لخيولك على أساس محتوى العلف من الطاقة قد تكون مضللة. فقد يكون العلف الذي يحتوي على نسبة عالية من الألياف ونسبة منخفضة من الطاقة مناسبا للخيول التي تعاني من زيادة الوزن لأنه قد يحد من تناول العلف ولكن العلف لا يعطينا مؤشرا جيدا على مدى قابلية هضم العلف أو مدى استعداد الحصان لتناوله. ومع ذلك فإن العلف الذي يحتوي على نسبة عالية من الألياف ونسبة منخفضة من الطاقة لا يزال قادرا على توفير قدر كبير من الطاقة لخيولنا من خلال تخمير أجزاء الألياف بواسطة الميكروبات المفيدة التي تستعمر الأمعاء الخلفية.