Study Notes on Vitamin and Mineral Metabolism and Function for Companion Animals

Module Overview

Instructor Information

  • Maria R. C. de Godoy

  • Associate Professor, Department of Animal Sciences

  • ANSC 422: Companion Animal Nutrition

Learning Objectives

  • Vitamins

    • Describe differences between fat- and water-soluble vitamins

    • List primary functions and sources of:

    • Vitamin A

    • Vitamin D (and aspects of metabolism in cats and dogs)

    • Vitamin E and K

    • B-vitamins

    • Choline

    • Vitamin C

  • Minerals

    • List primary functions and sources of calcium and phosphorus

    • Describe differences in large-breed dog diets regarding mineral and energy content

    • Understand macro- and microminerals in pet foods

Vitamins and Minerals

  • Many unknown aspects regarding dog and cat requirements

  • Focus on basics relevant to the industry

  • Many commercial foods provide recommended nutrient levels via premixes

    • Contributions from other ingredients sometimes ignored

    • Few deficiencies observed

  • Homemade diets have infrequent recalls

  • Imbalances in nutrient content may arise

Overview of Vitamins

General Characteristics

  • Vitamins are organic compounds (contain carbon)

  • Not utilized for energy but are essential in small dietary amounts to sustain metabolic functions

  • Some act as enzyme precursors or co-enzymes

Requirements

  • Many requirements unknown, only applicable in specific physiological states

  • Research limited due to animal welfare concerns and funding limitations

Fat-Soluble Vitamins

Key Vitamins

  • Vitamins A, D, E, and K

    • Digestion and absorption mechanisms similar to dietary lipids

    • Metabolites are excreted in feces via bile

    • Can be stored in the body (e.g., liver)

    • Potential for toxicity exists

    • Maximum recommendations given specifically for Vitamin A and D (set by AAFCO and NRC)

Specific Recommendations

Conversions

  • Vitamin D3: 1 microgram (μg) = 40 IU

  • Vitamin E: 1 IU = 1 mg α-tocopheryl acetate

Dog Fat Soluble Vitamin Recommendations

  • Vitamin A

    • Minimum Requirement: 5,000 IU/kg

    • Maximum: 250,000 IU/kg

    • Adequate Intake: 1,212 RE (Retinol Equivalents)

    • Recommended Allowance: 1,515 RE

    • Safe Upper Limit: 64,000 µg

  • Vitamin D3 (Cholecalciferol)

    • Minimum Requirement: 500 IU/kg

    • Maximum: 3,000 IU/kg

    • Recommended Allowance: 11 μg

    • Safe Upper Limit: 80 μg/kg

  • Vitamin E (α-tocopherol)

    • Minimum Requirement: 50 IU/kg

    • Recommended Allowance: 24 mg

    • Safe Maximum: 30 mg

  • Vitamin K (menaquinone)

    • Minimum Requirement: 1.3 mg

    • Recommended Allowance: 1.63 mg

Vitamin A

Forms and Functions

  • Many forms include: retinol, retinal, retinyl esters, retinoic acid

  • Primary roles include:

    • Vision

    • Tooth/bone growth

    • Reproduction

    • Maintenance of epithelial tissues (skin, gut, respiratory tract)

    • Immune function through cell proliferation and differentiation

Precursors

  • Plant carotenoids such as β-carotene can be metabolized into Vitamin A

  • High concentrations found in carrots, pumpkin, sweet potatoes

Beta-Carotene

Conversion Process

  • Conversion from β-carotene to Vitamin A varies

    • Efficient in herbivores

    • Dogs can utilize it

    • Cats lack the enzymes for conversion, requiring preformed Vitamin A

  • Absorption not regulated, leading to potential toxicity

Sources of Preformed Vitamin A

  • Animal products (liver, kidney, fish oils) are significant sources

  • Crystalline forms are often added to pet foods (retinyl acetate/palmitate)

Toxicity and Deficiency

  • Supplements are typically unnecessary due to potential preformed Vitamin A toxicity, which can lead to deformities

  • Care must be taken in homemade diets to avoid excessive vitamin A intake

  • Deficiency can lead to impaired growth, reproductive failure, and poor epithelial integrity

Vitamin D

Role and Functions

  • Major role in calcium and phosphorus homeostasis

    • Interacts with parathyroid hormone and calcitonin

    • Essential for bone, teeth, muscle contraction, blood clotting

  • Dietary forms are inactive; must undergo activation

Dietary Forms

  • Cholecalciferol (Vitamin D3) from animal sources

  • Ergocalciferol (Vitamin D2) from plant sources

Activation Process

  • Vitamin D must be hydroxylated to become biologically active; processes involve enzymes like 25-hydroxylase

Sources of Vitamin D

  • Skin produces vitamin D upon UV exposure (7-dehydrocholesterol to cholecalciferol)

Deficiency Consequences

  • Observations of deficiency leading to rickets in kittens and other issues in dogs

Supplementation

  • Common dietary sources include liver, meat, eggs, and some fish

Vitamin E

Functions and Characteristics

  • Major lipid-soluble antioxidant in the body

    • Scavenges free radicals and reduces oxidative damage

  • Functions beyond antioxidant properties, including prostaglandin synthesis and protein kinase regulation

Dietary Requirements

  • Dependent on free radical production rates, PUFA composition, and presence of other protective nutrients

    • Sources of Vitamin E include wheat germ, corn, soybean oil

Deficiency and Toxicity

  • Deficiency may present as reproductive failure, pansteatitis (yellow-brown adipose tissue inflammation)

  • Toxicity is rare but can interfere with other vitamins absorption

Vitamin K

General Overview

  • Functions primarily in blood clotting

  • Forms include phylloquinone (K1), menaquinone (K2), menadione (K3)

Sources

  • Intestinal bacteria typically synthesize enough vitamin K

  • Common sources in diets: liver, leafy greens, and fish

Toxicity and Deficiency

  • Deficiency is rare, generally presenting with prolonged clotting time and hemorrhage

  • No recorded toxicity reported

Water-Soluble Vitamins

Overview

  • Includes B-complex vitamins and Vitamin C

  • Absorption varies with concentration, little stored in the body (exception being Vitamin B12)

Recommendations for Dogs

  • Detailed recommendations provided for each vitamin, focusing on dietary amounts and safety

Recommendations for Cats

  • Similar considerations for dietary requirements and sources for B vitamins

Functions and Deficiency Symptoms

  • B vitamins serve as cofactors or coenzymes in metabolic processes

  • Examples of individual B vitamins such as Thiamin, Riboflavin, Niacin, Pantothenic Acid, and their associated roles, sources, and consequences of deficiency

Minerals

Types and Importance

  • Divided into macrominerals and microminerals based on dietary requirements

  • Essential for maintaining key physiological functions and biochemical pathways

Recommendations for Dogs and Cats

  • Detailed recommendations for macrominerals and microminerals, including sources and safe upper limits

Calcium and Phosphorus

Calcium Functions

  • Most abundant mineral, crucial for bone health and blood functions

  • Regulation via Vitamin D and parathyroid hormone

Phosphorus Functions

  • Second most abundant mineral, important for energy metabolism and skeletal structure

Conclusion

  • The proper understanding of vitamins and minerals in canine and feline nutrition is crucial for health and disease prevention. Proper intake levels can prevent deficiencies and toxicities, ensuring optimal health in companion animals.