Nutrition requirements change throughout life –growth –pregnancy –lactation –work essential nutrients –protein –**carbohydrates –**fat –**minerals –**vitamins –**H 2 O

Protein AA - compounds of muscle, enzymes and hormone 8-10% protein for mature horse –ample protein with high quality hay and grain –poor hay - add SBM, or oilseed products quality hay –limiting AA - lysine and methionine –excess methionine depletes copper and zinc (hoof wall) exercise - little if any increase needed –usually met with increase of ration excessive protein - increased fluid loss in sweat and urine –need more H 2 O

Carbohydrate primary source in equine diet consist of carbon, hydrogen and oxygen –sugars, starches, celluloses absorbed from intestine as glucose glucose stimulates insulin release, which lowers blood glucose peak levels of glucose and insulin about 2 hours after feeding - normal in 5 hours excess CHO stored as glycogen in muscle or liver exercise - increase grain to hay ratio to increase energy available

Fat concentrated source of energy - twice the calories as CHO composed of carbon, hydrogen and oxygen as fatty acids feed fat to provide 5-15% of energy in diet –add fat supplement - raise energy content of ration without increasing volume –in pelleted feeds - rancidity digest and utilize fats readily - 90% absorbed from intestine into bloodstream stored as triglycerides in muscle or adipose tissue - principal source for aerobic metabolism

Minerals inorganic substances formation of structural components and energy transfer exercise –maintain osmotic pressure and fluid balance –activity of nervous and muscular systems macrominerals –calcium, phosphorus, potassium, sodium, chloride, magnesium, sulfur microminerals –cobalt, copper, fluorine, iodine, iron, manganese, selenium, zinc

exercise - sodium, potassium, chloride –calcium, phosphorus, magnesium and zinc excess excreted in urine over-supplementation –one mineral prevents absorption of another –zinc inhibits calcium and copper absorption –calcium inhibits zinc absorption –manganese interferes with iron absorption

calcium –35% of bone structure –essential for muscle contraction –formation of hoof wall –20 g/day –exercise - increase calcium met with increase in feed –hay legumes are high in calcium grass and grain diet - add calcium carbonate (limestone)

phosphorus –15% of skeleton –require for energy transfer reaction - ATP and ADP –15 g/day –calcium:phosphorus ratio 1:1 potassium –major intracellular cation –maintain osmotic pressure and acid-base balance –25 g/day to 45 g/day (hard work) –hays - high in potassium –grains - low potassium (.3-.4%)

sodium –major extracellular cation –maintain acid base balance and osmotic regulation –7.5 g/day for idle horse –feeds lower than.1 % sodium –add sodium chloride (salt) –large increase required with exercise –can tolerate high levels of salt –free access to water chloride –extracellular anion –acid base balance and osmotic regulation –no requirement established yet –requirement met with salt

magnesium –.05% of body mass 60% for skeleton –activator of enzymes –7.5 g/day –requirement increases for hard working horses iron –constituent of hemoglobin –limited info on requirements –adequate amount from feed –anemia - iron deficiency

selenium –component of enzyme glutathione peroxidase cell membrane damage –.1 mg/kg of the diet –deficient geographic areas –horses absorb selenium efficiently (77%) / ruminants (29%) –deficiency may limit horse’s performance –can be toxic - 2 mg/kg of the diet