Nutrition

• requirements change throughout life

– growth

– pregnancy

– lactation

– work

• essential nutrients

– protein

– **carbohydrates

– **fat

– **minerals

– **vitamins

– **H2O

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 H2O

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