Slides-Metabolic RatesSV

The Burden of Food

• Discussion centered around animal physiology, particularly regarding metabolic rates and energy expenditure.

Indirect Calorimetry Theory

• Represents the conversion of glucose (C6H14O6) into carbon dioxide (CO2) and water (H2O) with an energy yield of 2820 kJ/mol.

• Indicates the measurement of energy expenditure through oxygen consumption.

Indirect Calorimetry

Respirometry

• Involves the use of various sensors and data acquisition systems to measure respiratory gases.

• Components of the Apparatus:

  • Holding Tank: Contains the sample.

  • Air Pumps and Sensors: Monitor the levels of pO2 and temperature (T).

  • Flush Pump and Solenoid Valves: Control air flow within the system.

Key Factors in Metabolic Rates

Factors Affecting Metabolic Rate

• Significant Factors:

  • Physical activity (e.g., running speed)

  • Environmental temperature

• Minor Factors:

  • Meal ingestion (especially protein-rich meals)

  • Body size, age, gender, O2 levels, hormonal status, time of day, and salinity for aquatic animals.

Specific Dynamic Action (SDA)

SDA Concept

• Describes the increase in metabolic rate after food ingestion.

• Graph Illustration: Shows the distinct metabolic responses to meal consumption over time.

SDA in Flatfish

• Demonstrates O2 consumption post-meal over a multi-hour timeline.

Standardization of Metabolic Rates

Basal Metabolic Rate (BMR)

• Refers to the metabolic rate of mammals and birds in a thermoneutral zone during fasting and resting.

Standard Metabolic Rate (SMR)

• Relates to amphibians, most fish, and mollusks while fasting and resting.

• Routine Metabolic Rate (RMR) is identified in fishes.

Effect of Body Size on Food Requirements

Comparison of Different Species

• Example Case Studies: Meadow vole vs. white rhino demonstrating food needs correlated with body size.

Metabolic Rate and Body Weight

Whole-body BMR within Various Species

• Discusses the relationship between whole-body metabolic rates and body weight across placental mammals.

Weight-specific BMR

• Highlights metabolic rates per gram across various sizes of mammals.

Metabolic Scaling

Allometric Relationships

• The equation M = aW^b where 'b' usually is less than 1, indicating diminishing metabolic returns relative to size increase within species.

Relation between Metabolic Rate and Body Size

Log-log Coordinates

• Analyzes species of mammals and crabs showing linear scaling in metabolic rates relative to body size.

Resting Heart Rate and Heart Size

Comparative Table of Mammals

• Shows the relationship of resting heart rate per unit body weight in various mammals.

Views of Mammalian Hearts

• Pictorial representation of heart size in animals indicating proportional relationship to their body size.

Herbivores in Mixed Communities

• Examines populations of herbivores coexisting in African grasslands and their biomass distribution.

Constraints and Scaling in Circulatory Systems

• Discusses fractal geometry's influence in the scaling of metabolic rates across species.

Net Growth Efficiency in Pacific Sardines

• Describes growth efficiency related to age in years.

Illustrating Energy Absorption Efficiency

• Defined as Absorbed energy divided by Ingested energy.

Practice Problems

1. Calculate the heat production of a dog based on O2 and CO2 measurements.

2. Discuss impacts of dietary design on SDA in poultry during hot conditions.

3. Methods for measuring metabolic rates in a growing young cow considering growth.

Pharmaceutical Testing Overview

• Importance of dose extrapolation between species in drug research context.

• Utilizes allometric scaling to estimate starting doses for clinical studies across species variations.

Dose Calculation Formula

• HED (mg/kg) = Animal NOAEL (mg/kg) x (Weight animal [kg] / Weight human [kg])^(-0.67)

• Provides depth on interspecies dose conversions.