1. ENERGY 2 Systems TDN Calories

2. GROSS ENERGY

3. Feces

4. GROSS ENERGY Feces DIGESTIBLE ENERGY

5. GROSS ENERGY Feces DIGESTIBLE ENERGY Urine & Gas

6. GROSS ENERGY Feces DIGESTIBLE ENERGY Urine & Gas METABOLIZABLE ENERGY

7. GROSS ENERGY Feces DIGESTIBLE ENERGY Urine & Gas METABOLIZABLE ENERGY Heat increment

8. GROSS ENERGY Feces DIGESTIBLE ENERGY Urine & Gas METABOLIZABLE ENERGY Heat increment NET ENERGY

9. GROSS ENERGY Feces DIGESTIBLE ENERGY Urine & Gas METABOLIZABLE ENERGY Heat increment NET ENERGY MaintenanceGainReproductionMilk Production

10. Gross Energy includes all the energy in a feed. It is not all available to the animal It is determined by how much heat is liberated upon combustion. Digestible Energy is how much energy does not end up in the feces. Therefore it was absorbed. It is not all used by the animal, some is lost. Metabolizable Energy is what is left after accounting for energy in feces, urine and gasses. It is still not all available for the animal to use.

11. Net Energy Is what is left after accounting for losses to feces, urine & gasses and heat increment. –Heat increment is energy lost in fermentation and in metabolic processes. Net Energy is available for the animal to use. It is not used with the same efficiency for all processes.

12. Net Energy is always used most efficiently for maintenance. Milk production is almost as efficient as maintenance. Gain (growth and fattening) is less efficient.

13. Different uses for energy require different values be used for the energy content of feeds for each purpose. Maintenance needs must always be met first This complicates ration balancing.

14. GROSS ENERGY Feces DIGESTIBLE ENERGY Urine & Gas METABOLIZABLE ENERGY Heat increment NET ENERGY MaintenanceGainReproductionMilk Production

15. Determining Caloric Energy Use Paar Adiabatic Bomb Calorimeter

16. Steps in determining calories Prepare sample (grind, pellet, place in bomb) Wire bomb and charge with Oxygen Place in calorimeter in known amount of H 2 O Measure initial temperature Ignite Measure final temperature

17. Calculations 1 calorie = energy to raise 1 g H 2 O 1° C 1000 cal = 1 Kcal –(In humans 1 Calorie = 1 Kcal, animal nutritionists don’t use Calorie vs calorie) Temp rise X g H 2 O = calories in sample Cal in sample X amount of feed = Cal in feed –same for feces

18. Calculate the total calories (or Kcal) (per day) eaten and excreted (in feces, urine). Calculate DE, ME, Net E (must know the endogenous contribution in Kcal/Kg and % –For Kcal/Kg divide the Kcal of interest by Kg consumed –For %, divide the Kcal of interest by Kcal of feed consumed (times 100).

19. TDN Total Digestible Nutrients –Forget that, I consider it a misnomer –It is really: An ENERGY INDEX on a carbohydrate equivalent basis Calculated from proximate analysis

20. Calculating TDN % CP X Digestibility =x % EE X 2.25 X Digestibility = x % CF X Digestibility = x % NFE X Digestibility = x ------ SUM = TDN TDN

21. Example Water12 Nitrogen 2 Ether Extract 4 Crude Fiber 10 Ash 2 NFE

22. Example Water12 Nitrogen 2 (2*6.25) 12.5 Ether Extract 4 Crude Fiber 10 Ash 2 NFE

23. Example Water12 Nitrogen 2 (2*6.25) 12.5 Ether Extract 4 Crude Fiber 10 Ash 2 NFE 59.5

24. Example Water12 Nitrogen 2 (2*6.25) 12.5.80 Ether Extract 4.75 Crude Fiber 10.40 Ash 2 NFE 59.5.80 digestibility

25. Example Water12 Nitrogen 2 (2*6.25) 12.5.80 = 10 Ether Extract 4 * 2.25 *.75 =6.75 Crude Fiber 10.40 = 4 Ash 2 NFE 59.5.80 = 47.6 ----------------- TOTAL (TDN)68.35 digestibility