Animal Nutrition

Animal Diet Requirements

  • An animal’s diet must supply:

    • Chemical energy for cellular processes

    • Organic building blocks for macromolecules

    • Essential nutrients

Essential Nutrients

  • Definition: Materials that an animal requires but cannot assemble from simple organic molecules.

  • Acquisition: Must be obtained from an animal’s diet.

  • Classes of Essential Nutrients:

    • Essential amino acids

    • Essential fatty acids

    • Vitamins

    • Minerals

Essential Amino Acids

  • All organisms require 20 amino acids.

  • Production:

    • Plants and microorganisms can usually produce all 20.

    • Animals can synthesize about half from dietary sources.

  • Sources:

    • Complete proteins (contain all essential amino acids): Meat, eggs, cheese.

    • Incomplete proteins (lack one or more essential amino acids): Most plant proteins.

  • Vegetarian Diets:

    • Can obtain all essential amino acids with a varied diet of plant proteins.

    • Remaining essential amino acids must be obtained in prefabricated form through food intake.

Essential Fatty Acids

  • Definition: Fatty acids that must be obtained from the diet, particularly certain unsaturated fatty acids (having one or more double bonds).

  • Synthesis: Animals can synthesize many fatty acids they need.

  • Sources: Seeds, grains, and vegetables are rich in essential fatty acids.

Vitamins

  • Definition: Organic molecules required in the diet in very small amounts.

  • Essential Vitamins for Humans: 13 distinct vitamins.

  • Classification:

    • Fat-soluble vitamins

    • Water-soluble vitamins

Vitamin Requirements of Humans

Vitamin

Major Dietary Sources

Major Functions in the Body

Symptoms of Deficiency

Water-Soluble Vitamins

B₁ (thiamine)

Pork, legumes, peanuts, whole grains

Coenzyme used in removing CO₂ from organic compounds

Beriberi (tingling, poor coordination, reduced heart function)

B₂ (riboflavin)

Dairy products, meats, enriched grains, vegetables

Component of coenzymes FAD and FMN

Skin lesions, such as cracks at corners of mouth

B₃ (niacin)

Nuts, meats, grains

Component of coenzymes NAD+ and NADP+

Skin and gastrointestinal lesions, delusions, confusion

B₅ (pantothenic acid)

Meats, dairy products, whole grains, fruits, vegetables

Component of coenzyme A

Fatigue, numbness, tingling of hands and feet

B₆ (pyridoxine)

Legumes, other vegetables, meats

Coenzyme in amino acid metabolism

Irritability, convulsions, muscular twitching, anemia

B₇ (biotin)

Green vegetables, oranges, nuts, legumes, whole grains

Coenzyme in nucleic acid and amino acid metabolism

Scaly skin inflammation, neuromuscular disorders

B₉ (folic acid)

Meats, eggs, dairy products

Production of nucleic acids and red blood cells

Anemia, neural tube malformation in fetus

B₁₂ (cobalamin)

Citrus fruits, broccoli, tomatoes

Used in collagen synthesis; antioxidant

Anemia, numbness, loss of balance

C (ascorbic acid)

Dark green and orange vegetables and fruits, dairy products

Component of visual pigments; maintenance of epithelial tissues

Scurvy (degeneration of skin and teeth), delayed wound healing

Fat-Soluble Vitamins

A (retinol)

Dairy products, egg yolk

Aids in absorption and use of calcium and phosphorus

Blindness, skin disorders, impaired immunity

D

Vegetable oils, nuts, seeds

Important in blood clotting

Rickets (bone deformities) in children, bone softening in adults

E (tocopherol)

Green vegetables, tea; also made by colon bacteria

Antioxidant; helps prevent damage to cell membranes

Nervous system degeneration

K (phylloquinone)

Important in blood clotting

Defective blood clotting

Minerals

  • Definition: Simple inorganic nutrients usually required in small amounts.

  • Caution: Ingesting large amounts can upset homeostatic balance.

Mineral Requirements of Humans

Mineral

Major Dietary Sources

Major Functions in the Body

Symptoms of Deficiency

Calcium (Ca)

Dairy products, dark green vegetables, legumes

Bone and tooth formation, blood clotting, nerve and muscle function

Impaired growth, loss of bone mass

Phosphorus (P)

Dairy products, meats, grains

Bone and tooth formation, acid-base balance, nucleotide synthesis

Weakness, loss of minerals from bone, calcium loss

Sulfur (S)

Proteins from many sources

Component of certain amino acids

Impaired growth, fatigue, swelling

Potassium (K)

Meats, dairy products, many fruits and vegetables, grains

Acid-base balance, water balance, nerve function

Muscular weakness, paralysis, nausea, heart failure

Chlorine (Cl)

Table salt

Acid-base balance, formation of gastric juice, nerve function, osmotic balance

Muscle cramps, reduced appetite

Sodium (Na)

Table salt

Acid-base balance, water balance, nerve function

Muscle cramps, reduced appetite

Magnesium (Mg)

Whole grains, green leafy vegetables

Enzyme cofactor; ATP bioenergetics

Nervous system disturbances

Iron (Fe)

Meats, eggs, legumes, whole grains, green leafy vegetables

Component of hemoglobin and of electron carriers; enzyme cofactor

Iron-deficiency anemia, weakness, impaired immunity

Fluorine (F)

Drinking water, tea, seafood

Maintenance of tooth structure

Higher frequency of tooth decay

Iodine (I)

Seafood, iodized salt

Component of thyroid hormones

Goiter (enlarged thyroid gland)

  • Additional minerals: Required in trace amounts include cobalt (Co), copper (Cu), manganese (Mn), molybdenum (Mo), selenium (Se), and zinc (Zn).

  • Caution: All minerals can be harmful in excess.

Dietary Variations

  • Diverse Diets:

    • Herbivores: Mainly consume plants or algae.

    • Carnivores: Primarily eat other animals.

    • Omnivores: Regularly consume both animals and plants/algae.

  • Feeding Behavior:

    • Most animals are opportunistic feeders, broadening their diet as necessary.

Undernourishment

  • Definition: Occurs when a diet does not provide enough chemical energy.

  • Consequences of Undernourishment:

    • Uses up stored fat and carbohydrates.

    • Breaks down individual proteins.

    • Loses muscle mass.

    • Suffers protein deficiency in the brain.

    • Can lead to death or irreversible damage.

Food Processing Steps

  • Stages of Food Processing:

    1. Ingestion: The act of eating or feeding.

    2. Digestion: Breakdown of food into simpler components.

    3. Absorption: Uptake of nutrients into the body.

    4. Elimination: Disposal of indigestible parts of food.

Feeding Mechanisms

  • Filter Feeders:

    • Many aquatic animals filter small food particles from the surrounding medium.

  • Substrate Feeders:

    • Live in or on their food source.

  • Fluid Feeders:

    • Suck nutrient-rich fluid from a living host.

  • Bulk Feeders:

    • Eat relatively large pieces of food, common in most animals and humans.

Digestive Compartments

  • Most animals have specialized compartments to process food.

  • Reduces the risk of digesting their own cells and tissues.

  • More complex animals have a complete digestive tract with two openings (mouth and anus).

  • Complete Digestive Tract: Also known as the alimentary canal.

Human Digestive System

  • Components:

    • Mouth (oral cavity)

    • Pharynx

    • Esophagus

    • Stomach

    • Small intestine (duodenum, jejunum, ileum)

    • Large intestine (cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus)

    • Accessory organs: liver, gallbladder, pancreas, salivary glands (parotid gland, sublingual gland, submandibular gland)

Digestive Phases in Humans

  • Carbohydrate Digestion:

    • Polysaccharides (starch, glycogen) → Disaccharides via salivary amylase → Smaller polysaccharides → Maltose.

  • Protein Digestion:

    • Proteins → Small polypeptides via pepsin in the stomach → Smaller polypeptides → Dipeptidases and carboxypeptidase in the small intestine.

  • Nucleic Acid Digestion:

    • DNA, RNA → Nucleotides via pancreatic nucleases.

  • Fat Digestion:

    • Fat (triglycerides) → Glycerol and fatty acids via pancreatic lipase.

Evolutionary Adaptations in Digestive Systems

  • Digestive system variations correlate with dietary habits.

  • Stomach and Intestinal Adaptations:

    • Many carnivores have larger, expandable stomachs.

    • Herbivores and omnivores generally possess longer alimentary canals than carnivores due to the need for longer digestion time for vegetation.

Mutualistic Adaptations

  • Mutualism with Bacteria:

    • Coexistence of humans and many gut bacteria functions symbiotically.

    • Some intestinal bacteria produce vitamins and regulate the development of intestinal epithelium and the immune system.

Specialized Diets in Herbivores

  • Organisms primarily consuming cellulose develop fermentation chambers for digestion via mutualistic microorganisms.

  • Ruminants: Exhibit advanced adaptations for herbivorous diets, passing food through their alimentary canal twice to recover vital nutrients.

No Digestive System

  • Example: Giant tubeworms possess no digestive system; they obtain nutrients from mutualistic bacteria residing within their bodies.