Energy Concepts

energy

utilization of chemical energy

nutritional usage, head produced upon oxidation

1st Law: Conservation of Energy

energy cannot be created or destroyed

energy input must = energy output ± change in body energy

retained energy (RE) = GE - FE - UE - GPD - HP

• gaseous products of digestion

• heat produced

2nd Law: Entropy of the universe always increases

no transformation of energy is 100% efficient and the inefficiencies are lost as heat

energy from nutrients

carbohydrates: 3.7-4.3 kcal/g

fats: 6.5-9.9 kcal/g

proteins: 4.0-8.3 kcal/g

can also be derived from breakdown of body tissues

energy balance

difference between intake and expenditure

positive - intake>expenditure (growth, overfeeding)

negative - intake<expenditure

maintenance - intake=expenditure

bomb calorimeter (adiabatic)

measures the complete transduction of chemical energy to heat

describes a feed ingredient’s gross energy

GE kcal/g

• carbs - 4.15

• protein - 5.65

• fat - 9.4

does not tell of bio availability

transformation of energy (flow of energy through the body)

Gross energy (GE) - max energy

Digestible energy (DE) = GE - GEfeces (energy lost in feces)

Metabolizable energy (ME) = DE - GEurine - GEgas

Net energy = ME - Hi (heat loss)

determine ME

Calculate ME from factors

most common, makes assumptions about GE and nutrient digestibility

Practicle equations for predicting diet ME: Atwater

modified equation for pet foods reflects lower digestibility

provides estimate/starting point