Question

Which component of the energy in the food less the energy lost in faeces, urine and gills?

• A. Metabolizable energy
• B. Gross energy
• C. Basal energy
• D. Net energy

Hint:

Remember the progression: - Gross $\rightarrow$ less Feces = Digestible.
- Digestible $\rightarrow$ less Urine & Gill Excretions = Metabolizable.
- Metabolizable $\rightarrow$ less Heat Increment = Net.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The partition of dietary energy in fish is tracked through a series of energy losses.
Gross energy ingested is progressively reduced by losses in feces, urine, gill excretions, and metabolic heat to yield the energy available for growth and maintenance.
Detailed Explanation:
The biological partitioning of energy in fish follows this pathway:
1. Gross Energy (GE): The total chemical energy in the ingested food.
2. Digestible Energy (DE): Energy remaining after subtracting fecal energy loss.
\[ \text{DE} = \text{GE} - \text{Fecal Energy} \] 3. Metabolizable Energy (ME): Energy remaining after subtracting urinary energy loss and branchial (gill) excretion losses from digestible energy.
In fish, ammonia is excreted primarily across the gills, representing a significant loss of energy.
\[ \text{ME} = \text{DE} - (\text{Urinary Energy} + \text{Branchial Energy}) \] \[ \text{ME} = \text{GE} - (\text{Fecal} + \text{Urinary} + \text{Branchial Energy}) \] 4. Net Energy (NE): Energy remaining after subtracting the heat increment of feeding (SDA) from ME, which is used for maintenance and growth.
Therefore, food energy less the energy lost in feces, urine, and gills is Metabolizable energy.

Step 2: Final Answer:
The correct term is Metabolizable energy, corresponding to option (1).