ENERGY

2 Systems

TDN

Calories

GROSS ENERGY

GROSS ENERGY

Feces

GROSS ENERGY

Feces

DIGESTIBLE ENERGY

GROSS ENERGY

Feces

DIGESTIBLE ENERGY

Urine & Gas

GROSS ENERGY

Feces

DIGESTIBLE ENERGY

Urine & Gas

METABOLIZABLE ENERGY

GROSS ENERGY

Feces

DIGESTIBLE ENERGY

Urine & Gas

METABOLIZABLE ENERGY

Heat increment

GROSS ENERGY

Feces

DIGESTIBLE ENERGY

Urine & Gas

METABOLIZABLE ENERGY

Heat increment

NET ENERGY

GROSS ENERGY

Feces

DIGESTIBLE ENERGY

Urine & Gas

METABOLIZABLE ENERGY

Heat increment

NET ENERGY

Maintenance Gain ReproductionMilk Production

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.

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.

• Net Energy is always used most efficiently for maintenance.

• Milk production is almost as efficient as maintenance.

• Gain (growth and fattening) is less efficient.

• 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.

GROSS ENERGY

Feces

DIGESTIBLE ENERGY

Urine & Gas

METABOLIZABLE ENERGY

Heat increment

NET ENERGY

Maintenance Gain ReproductionMilk Production

Determining Caloric Energy

• Use Paar Adiabatic Bomb Calorimeter

Steps in determining calories

• Prepare sample (grind, pellet, place in bomb)

• Wire bomb and charge with Oxygen

• Place in calorimeter in known amount of H2O

• Measure initial temperature

• Ignite

• Measure final temperature

Calculations

• 1 calorie = energy to raise 1 g H2O 1° C

• 1000 cal = 1 Kcal– (In humans 1 Calorie = 1 Kcal, animal

nutritionists don’t use Calorie vs calorie)

• Temp rise X g H2O = calories in sample

• Cal in sample X amount of feed = Cal in feed– same for feces

• 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).

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

Calculating TDN

• % CP X Digestibility = x

• % EE X 2.25 X Digestibility = x

• % CF X Digestibility = x

• % NFE X Digestibility = x

• ------

• SUM = TDN TDN

Example

• Water 12

• Nitrogen 2

• Ether Extract 4

• Crude Fiber 10

• Ash 2

• NFE

Example

• Water 12

• Nitrogen 2 (2*6.25) 12.5

• Ether Extract 4

• Crude Fiber 10

• Ash 2

• NFE

Example

• Water 12

• Nitrogen 2 (2*6.25) 12.5

• Ether Extract 4

• Crude Fiber 10

• Ash 2

• NFE 59.5

Example

• Water 12

• Nitrogen 2 (2*6.25) 12.5 .80

• Ether Extract 4 .75

• Crude Fiber 10 .40

• Ash 2

• NFE 59.5 .80

digestibility

Example

• Water 12• 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