Metabolism

[Jeffery Escobar]

In research setting, apparent metabolizable energy (AME) is calculated by subtracting the gross energy (GE) of excreta (i.e., feces + urine) from the gross energy of the feed consumed. GE is determined in aa adiabatic bomb calorimeter.

AMEdiet (kcal or MJ/kg diet) = [(Feed intake × GEdiet) − (Excreta output × GEexcreta)]/Feed intake.

Often, AME of ingredients are corrected for zero nitrogen (N) retention in birds to obtain nitrogen-corrected metabolizable energy (AMEn).

AMEndiet (kcal or MJ/kg) = AMEdiet − [N retention (g/kg) × Correction factor/1000]

[Mohamed Ismail]

Bomb calorie meter

[Md. Abdul Bari]

Metabolizable energy (ME) is measured by determining the difference between the total energy consumed and the energy lost in feces, urine, and gases (for some species). It is commonly measured in kilocalories (kcal) or megajoules (MJ) per unit of feed. The general process follows these steps:

1. Gross Energy (GE) Measurement

The total energy in a feed sample is determined using a bomb calorimeter, which burns the feed completely in an oxygen-rich environment to measure the heat released.

2. Digestible Energy (DE) Calculation

The energy lost in feces is measured by feeding the test diet to animals and collecting their feces.

The feces are analyzed using a bomb calorimeter to determine their energy content.

DE = GE – Energy lost in feces

3. Metabolizable Energy (ME) Calculation

The additional energy lost in urine and gaseous emissions (mainly methane in ruminants) is measured.

Urine energy is determined using a bomb calorimeter, while gas energy is estimated using indirect calorimetry.

ME = DE – (Energy lost in urine + Energy lost in gases)