Vitamins organic substances in natural foods produced within the body - synthesized by microbes stabled horses may need supplemental vitamins vitamin A –vision –cellular differentiation –bone remodeling –carotene destroyed by heat, light, wet hay, storage –may want to supplement in winter

Vitamin A deficiency –poor bone development –poor night vision –extreme deficiency excessive tear production infertility in mares –feeds supplemented 10,000 iu/kg toxic 5X

vitamin D –maintain calcium:phosphorus homeostasis blocking agents –synthesized in body with sunlight –deficiency of Vitamin D depressed blood Ca draws Ca from bone lameness bone fractures –requirements not established –deficiency and toxicity same symptoms

Vitamin E antioxidant value –related with selenium deficiencies associated with myopathies in foals requirements not established –? - hard-working horses may have muscular problems with deficiency destroyed with oxidation –moisture and storage –moldy hay –ground grains deficiency –neurological diseases

B complex vitamins –adequate in forages and synthesized by bacteria in LI –exceptions thiamine –role in energy metabolism –heavy exercise may be marginal deficiency –deficiency ? lack of coordination in hind end heart problems folic acid –decrease with months of intense exercise –decrease with prolonged stabling –give access to pasture

B 12 –contains cobalt –deficient areas deficient in ruminants ? anemia and decreased RBC in horses biotin –water soluble –availability wheat, barley, milo: low oats : medium corn : available –deficiency cracked hooves –15 mg/day

water –most important nutrient –lack of H 2 O more serious than any other nutrient –lost in urine, feces, sweat, evaporation –increased water consumption with hay and grain –idle horse drinks 28 liters/day - cool weather –“ “ “ 80 liters/day - hot weather –increased water intake with exercise 3 % of BW loss of water affects performance 5-10% of BW loss during endurance race

Ration Formulation ration dependent on level of activity –idle horse - good roughage and salt/mineral block 450 kg horse needs about 15,000 kcal/day energy –exercising horse - roughage and concentrate energy increase usually fulfills protein, vitamin and mineral increase, except calcium –increase energy intake by adding fat

“calorie” - = 1 kilocalorie –amount of energy required as heat to raise the temperature of 1 kg of water by 1 o C –1000 kcal in 1 megacalorie (Mcal) –DE and TDN –% BW.5 % BW/day as roughage

Sprinting Vs. Endurance grain:hay ratio varies sprint –maximum hay/day 1.5% BW hay retains a lot of water in the gut endurance –advantageous to feed hay to 2% BW retains water –add fat (up to 15 % of total ration)

Day of Competition H 2 O available at all times endurance/eventing –feed hay and grain 4 hours prior to competition glucose and insulin stabilize continuous water electrolytes sprinting sports –also 4 hours prior to competition

Glycogen Loading enhance performance by delaying glycogen depletion manipulation of diet in humans –exhaustive exercise - low CHO diet –light exercise - high CHO diet replenish glycogen over normal resting stores horse –conditioned horse has large amounts of glycogen –high CHO diet - laminitis or tying-up

Table 13.1 and 13.2