ANS 230: Net Energy Concept - Thermodynamics I and II

How is 'energy' defined in the context of animal nutrition?

The capacity to do work, which is contained within the chemical bonds of nutrients.

Which three nutrient classes contain the chemical energy used by animals?

Fats, carbohydrates, and proteins.

Cells interconvert chemical energy from feed into mechanical, electrical, or _____ energy.

heat

Approximately what percentage of feed energy is typically used for basal metabolism (maintenance)?

More than $50\%$.

Why did early researchers like Lavoisier equate animal metabolism to a 'flame'?

Because both processes consume oxygen ($O_{2}$) and produce heat.

State the First Law of Thermodynamics as it applies to animal bioenergetics.

Energy can neither be created nor destroyed, only interconverted.

According to the Second Law of Thermodynamics, why is no energy transformation $100\%$ efficient?

Entropy always increases, meaning some energy is always lost as heat.

How does the Theory of Relativity ($E = mc^{2}$) assist nutritionists in measuring feed?

It allows the conversion of mass measurements (e.g., pounds of feed) into energy measures (calories).

Concept: Direct Calorimetry

Definition: A method that measures heat production directly. Example: Measuring the volume of water produced by an animal's body heat melting ice.

_____ calorimetry estimates heat production by measuring oxygen consumption and carbon dioxide production.

Indirect

In indirect calorimetry, what does the 'RQ' (Respiratory Quotient) represent?

The ratio of $CO_{2}$ produced to $O_{2}$ consumed.

Define Gross Energy ($GE$).

The total energy released as heat when a substrate is fully oxidized.

What device is used to measure the Gross Energy of a substrate?

A bomb calorimeter.

What is the approximate Gross Energy yield of carbohydrates or starch?

$4$ to $4.1$ $kcal/g$.

What is the Gross Energy yield of protein in biological systems?

Approximately $4$ $kcal/g$.

What is the approximate Gross Energy yield of fat?

$9$ to $9.4$ $kcal/g$.

Formula: Gross Energy ($kcal/kg$)

$GE = (\% \text{Fat} \times 9.4) + (\% \text{Starch} \times 4.1) + (\% \text{Protein} \times 5.4)$

Digestible Energy ($DE$) is calculated by subtracting _____ energy from Gross Energy ($GE$).

fecal

What two types of energy loss occur between Digestible Energy ($DE$) and Metabolizable Energy ($ME$)?

Urine energy and gaseous energy ($CH_{4}$).

Which specific organisms in the gastrointestinal tract produce gaseous energy loss?

Microbes.

Metabolizable Energy ($ME$) minus _____ equals Net Energy ($NE$).

Heat Increment ($HI$)

The inefficiency of energy use, representing heat given off during digestion and metabolism above maintenance, is called the _____.

Heat Increment ($HI$)

What are two alternative names for Heat Increment ($HI$)?

Specific dynamic action or dietary thermogenesis.

List the four primary sources of Heat Increment.

Digestion, fermentation, waste product formation, and nutrient metabolism.

Why is measuring heat production necessary for determining Net Energy ($NE$)?

Because $NE$ is calculated by subtracting total heat production (including $HI$) from intake energy.

Net Energy is categorized into $NE_{m}$, $NE_{g}$, and $NE_{l}$, which stand for maintenance, gain, and _____.

lactation

Total Heat Production is an indicator of energy expenditure and is composed of basal metabolism, GI microbes, and the _____ of feeding.

Heat Increment

What formula represents 'metabolic body size,' used to relate body weight to energy expenditure?

$BW^{0.75}$

Why do ruminants typically have different metabolic rates in the GI tract compared to non-ruminants?

Because the ruminant GI tract involves significant energy-consuming fermentation processes.

Improving the efficiency of dietary energy use is essential for reducing costs and minimizing _____.

environmental (or nutrient) waste

Concept: Precision Feeding

Definition: Formulating diets using Net Energy values to more accurately meet an animal's specific status and requirements.

In energy partitioning, which loss accounts for the largest difference between $GE$ and $DE$?

Fecal loss.

Which energy loss is specifically associated with the formation of urea or other nitrogenous products?

Urine energy (waste product formation).

True or False: The Heat Increment ($HI$) is consistent across all animal species and feed types.

False; it varies significantly based on species and the specific diet consumed.

In a bomb calorimeter, what is the 'multiplier' used to calculate the energy contribution of protein?

$5.4$.

According to the summary, energy is not a nutrient itself but is _____ within nutrients.

contained

What is the primary function of the face-mask used in some indirect calorimetry studies?

To capture and measure gas exchange ($O_{2}$ and $CO_{2}$) for estimating metabolic activity.

Under the First Law of Thermodynamics, when chemical energy from feed is used by cells, it is not lost but _____.

interconverted (into mechanical, electrical, or heat energy)

Which energy value ($GE, DE, ME, \text{ or } NE$) is the most accurate for predicting the energy available for animal production?

Net Energy ($NE$).

In the 'Biological Flame' analogy, the consumption of which gas is used as a measure of metabolic activity?

Oxygen ($O_{2}$).