1. Body Condition Changes • Too high BCS • Heavier, maintenance higher • Require more feed – produce more heat • Excess fat decreases heat loss • Higher heart rate • Recover more slowly

2. Body Condition Changes • 16 to 20 kg per BCS increase/decrease • 16 to 24 Mcal DE required per kg gain • Less at lower BCS • More at higher BCS

3. Body Condition Changes • Less at lower BCS • 18 kg per BCS increase • 16 Mcal DE required per kg gain • 18 kg x 16 Mcal DE/kg = 288 Mcal

4. Body Condition Changes • More at higher BCS • 18 kg per BCS increase • 24 Mcal DE required per kg gain • 18 kg x 24 Mcal DE/kg = 432 Mcal

5. Body Condition Changes 500 kg mature horse, BCS 4 to 5

6. Physical Activity • Sprint activity • 1 min or less at 100% maximum exertion intensity • QH racing, barrel racing, rodeo events • Requires primarily anaerobic energy production

7. Physical Activity • Middle distances • Several minutes at 75-95% maximum exertion intensity • TB racing, Standardbred trotter racing • Requires both aerobic and anaerobic energy production

8. Physical Activity • Endurance • 2 h or more, low-intensity • Endurance, trail rides, ranch work, lesson horses, most show horses • Requires aerobic energy production

9. Energy Production • ATP used directly for muscle movement • Resynthesized immediately from creatine phosphate • Only enough for 6 to 8 sec maximum exertion • Amount not affected by diet

10. For More ATP: • 1. Glycolysis • Anaerobic metabolism of glucose or glycogen to lactic acid • Very rapid • But, only small amount ATP • Only a few minutes max exertion

11. For More ATP: • 2. Aerobic oxidation • Glucose, glycogen, fats, or protein to CO2 + H2O • Occurs more slowly • Much larger amount ATP • Prolonged activity

12. Sources of Energy