Mineral Absorption and Energy Calculations in Animal Nutrition

Overview of Mineral Absorption

  • Calcium Absorption:

    • Active absorption dependent on Vitamin D.
    • Involves calcium-binding protein (calbindin).
    • Passive absorption occurs in the jejunum but low in ruminants.

  • Phosphorus Absorption:

    • Facilitated in the duodenum via sodium transport, enhanced by sodium and phenophosphates.

  • Iron Absorption:

    • Excessive quantities can be toxic; reduced from ferric (Fe3+) to ferrous (Fe2+).
    • Divalent metal transporter for transfer.
    • Stored as ferritin, released by ferroportin to bind to transferrin.

  • Copper Absorption:

    • Two mechanisms: rapid low-capacity + slow high-capacity.
    • Facilitated diffusion with amino acids; binds to metallothionein.
    • Stimulation of absorption by zinc.

  • Selenium Regulation:

    • Only mineral regulated by FDA; excess is excreted.

  • Magnesium Absorption:

    • Occurs in the ileum and colon via passive diffusion.

  • Potassium Absorption:

    • Influenced by intracellular uptake and renal secretion; linked to insulin and sodium-potassium pump activity.

  • Vitamin Absorption:

    • Vitamins A, D, and E absorbed in small intestine and incorporated into lipoproteins (chylomicrons, VLDLs).

  • Water-soluble vitamins:

    • Absorbed via active and facilitated transport.

Energy Calculations in Animal Nutrition

  • Consumption Metrics: Dry matter intake (DMI) is critical for nutrient requirements.

  • Total Digestible Nutrients (TDN): Provides an energy estimate; 1 kg of TDN = 4.4 megacals digestible energy.

  • Energy Classes: Digestible Energy (DE) calculated from caloric intake; metabolizable energy (ME) accounts for losses in urine.

  • Net Energy (NE): Considers heat loss and energy used for maintenance and production.

Physiological Energy Requirements

  • Maintenance requirements higher when temperature drops.

  • Greater heat production in colder environments; efficiency reduces as animals age.

  • Body Maintenance Calculation:

    • Maintenance energy requirement can be determined with formulas based on weight.
    • Example: NE = 0.077 ME kg^0.75.

Metabolizable Protein (MP) and Rumen Functionality

  • MP defined as protein available for metabolism; crucial for animal growth and production.
  • Distinction between Rumen Degradable Protein (RDP) and Rumen Undegradable Protein (RUP).
  • Animal typically utilizes 80% of MP efficiently.

Practical Application in Nutrition Programs

  • Animal-specific Calculations: Specific formulas guide energy calculations; adjustments made for RDP and RUP based on dietary requirements.