Animal Nutrition

All living organisms consume food to obtain energy for daily activities and to carry out metabolic processes. While plants produce their own food, animals rely directly or indirectly on plants. The nutrients animals require are obtained from their diet.

Animal diets consist of six main groups of nutrients: carbohydrates, proteins, fats, vitamins, minerals, and water. Although fiber is not considered a nutrient, it is an essential component of a balanced diet for humans.

Carbohydrates

Carbohydrates are composed of carbon, hydrogen, and oxygen, with a hydrogen-to-oxygen ratio of 2:1. They range from simple monosaccharides, such as glucose and fructose, to complex polysaccharides like starch. Complex carbohydrates are formed through condensation reactions, where smaller molecules join to form a larger molecule with the removal of water (H₂O).

Examples of carbohydrate-rich foods: rice, potatoes, sweet potatoes, cassava, bread, millet, and sugary foods (e.g., cake, jam, honey).

Types of Carbohydrates

1. Monosaccharides: Simple sugars made up of one sugar unit.
   • Pentose: Sugars containing five carbon atoms, such as deoxyribose and ribose, which form the backbone of nucleic acids like DNA and RNA.
   • Hexose: Sugars with six carbon atoms arranged in a ring, including glucose, fructose, and galactose. These are key energy storage molecules with the formula C₆H₁₂O₆.
2. Disaccharides: Formed by the condensation of two monosaccharides, represented by the formula C₁₂H₂₂O₁₁.
   • Lactose: Glucose + Galactose → Lactose + H₂O (found in milk).
   • Maltose: Glucose + Glucose → Maltose + H₂O (found in grains and malted cereals).
   • Sucrose: Glucose + Fructose → Sucrose + H₂O (found in sugarcane stems, ripe fruits, and beets).
3. Polysaccharides: Long chains of monosaccharides formed through condensation, with the general formula (C₆H₁₀O₅)_n. They are insoluble and not sweet-tasting. Examples include cellulose, starch, and glycogen.

Importance of Carbohydrates

1. Carbohydrates are the primary source of energy for the body.
2. Their oxidation releases heat, which helps regulate body temperature.

Fats/Lipids

Fats, also known as lipids, are made up of carbon, hydrogen, and oxygen. Each fat molecule consists of one glycerol molecule bonded to three fatty acid molecules. Fats can be classified as saturated or unsaturated, based on the structure of their fatty acids.

Types of Fats

1. Saturated Fats: These fats have all carbon atoms in their fatty acid chains bonded to hydrogen atoms, with no carbon-carbon double bonds.
2. Unsaturated Fats: These fats contain one or more carbon-carbon double bonds, resulting in fewer hydrogen atoms. They can be further classified as:
   • Cis Fats: Naturally occurring unsaturated fats with hydrogen atoms on the same side of the double bond.
   • Trans Fats: Unsaturated fats with hydrogen atoms on opposite sides of the double bond, often found in processed foods.
   • Monounsaturated Fats: Contain one double bond.
   • Polyunsaturated Fats: Contain multiple double bonds.

Importance of Fats

1. Fats serve as energy storage molecules and provide more energy per gram than carbohydrates when metabolized.
2. They help regulate body temperature by providing thermal insulation. For example, marine animals in cold climates have a fat layer called blubber that helps them stay warm.
3. Fats are essential components of cell membranes.
4. They provide buoyancy to marine animals, such as whales, which have thick layers of blubber.
5. Fats act as solvents for fat-soluble vitamins and hormones.

Proteins

Proteins are large, complex molecules composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. They are made up of smaller units called amino acids. There are 25 types of amino acids, which occur in various numbers and sequences to form different types of proteins. Proteins play a vital role in building and repairing the body. Key sources of protein include:

• Animal-based sources: fish, meat, milk, eggs, and cheese.
• Plant-based sources: beans, groundnuts, and soybeans.

Amino acids are categorized into:

• Essential amino acids: Cannot be synthesized by the body and must be obtained from the diet.
• Non-essential amino acids: Can be produced by the body from other nitrogen-containing compounds.

Examples of essential amino acids:

• Lysine
• Tryptophan
• Phenylalanine
• Isoleucine
• Valine
• Methionine
• Leucine
• Threonine

Importance of Proteins

1. Vital for building and repairing body tissues.
2. Key components of cell membranes.
3. Necessary for the production of hormones and enzymes.
4. Essential for forming antibodies to fight infections.
5. Involved in the repair of cells and replacement of worn-out tissues.

Vitamins

Vitamins are organic compounds needed in small amounts for growth, development, and overall health. Most vitamins must be obtained through the diet, except for vitamin D, which the body can produce with UV radiation exposure. Common sources include fruits, vegetables, milk, eggs, and animal organs. A deficiency or excess of vitamins can lead to health problems.

Examples of Vitamins

1. Vitamin A (Retinol): Found in oils, egg yolk, green and yellow vegetables, and fish.
   • Functions: Supports healthy skin, body cell growth, and vision in dim light.
   • Deficiency: Causes flaky skin and night blindness.
2. Vitamin D: Synthesized in the skin with UV radiation exposure; also found in milk, eggs, and liver.
   • Functions: Aids in forming strong bones and teeth and enhances calcium and phosphorus absorption.
   • Deficiency: Leads to rickets and soft bones.
3. Vitamin E: Found in leafy green vegetables, seeds, eggs, and milk.
   • Functions: Promotes fertility and protects cell membranes from oxidation.
   • Deficiency: Causes sterility and premature abortion.
4. Vitamin K (Phylloquinone): Found in liver, green vegetables, and produced by intestinal bacteria.
   • Functions: Supports blood clotting.
   • Deficiency: Leads to severe bleeding due to poor clotting.
5. Vitamin C (Ascorbic Acid): Found in citrus fruits, guava, and papaya.
   • Functions: Strengthens immunity and supports connective tissue, bone, and dentine health.
   • Deficiency: Causes scurvy and slow wound healing.

Minerals

Minerals are chemical elements, apart from carbon, hydrogen, oxygen, and nitrogen, required by organisms for health. They are essential for various bodily functions and are primarily obtained through the diet. Examples include sodium, potassium, calcium, magnesium, iron, and phosphorus.

Deficiency of minerals: A lack of dietary minerals can result in poor health and deficiency diseases.

List of Minerals

1. Iron can be obtained from liver, spinach, eggs, and meat. Daily recommended intake: 10 mg
   • Functions:
   • Formation of hemoglobin in red blood cells
   • Production of myoglobin in muscle cells
   • Deficiency:
   • Tiredness
   • Anemia
2. Calcium can be obtained from milk, fish, and green vegetables. Daily recommended intake: 1 g
   • Functions:
   • Strengthens bones and teeth
   • Supports proper functioning of the heart and nervous system
   • Deficiency:
   • Rickets
   • Muscle weakness
3. Sodium can be obtained from salt, fish, and eggs. Daily recommended intake: 2,000 mg
   • Functions:
   • Maintains correct osmotic pressure of body fluids
   • Essential component of blood plasma
   • Required for nerve impulse transmission
   • Deficiency:
   • Dehydration
   • Kidney failure
   • Muscle cramps
4. Phosphorus can be obtained from eggs, milk, cheese, and fish. Daily recommended intake: 1.5 g
   • Functions:
   • Involved in energy transfer
   • Essential for RNA and DNA structure
   • Deficiency:
   • Rickets
   • Slow growth
5. Potassium is found in bananas, spinach, mushrooms, cucumbers, and peas. Daily recommended intake: 3,000 mg
   • Functions:
   • Supports muscle function
   • Regulates heartbeat
   • Deficiency:
   • Muscle paralysis
   • Heart palpitations
6. Chlorine is found in table salt and meat. Daily recommended intake: 3.1 g
   • Functions:
   • Regulates osmotic pressure and acid-base balance
   • Facilitates oxygen and carbon dioxide transport in the blood
   • Maintains digestive juice pH
   • Deficiency:
   • Weight loss
   • Decreased growth
   • Fluid loss
7. Iodine is found in dairy products, iodized salt, and eggs. Daily recommended intake: 150 mcg
   • Functions:
   • Required for thyroid gland function and thyroxine production
   • Deficiency:
   • Dry, flaky skin
   • Thinning hair

Water

Approximately 70% of the human body's non-fat mass is water. Water is consumed through food and drinks. Sources include metabolic water, rivers, rain, and springs. The body needs 1 to 7 liters of water daily, depending on activity levels, temperature, and humidity.

Importance of Water

1. Regulates body temperature through sweat
2. Maintains osmotic balance in tissues
3. Supports metabolic activities
4. Acts as a solvent for food digestion
5. Transports nutrients, excretory products, and hormones

Fibre

Dietary fibre is an indigestible carbohydrate, primarily cellulose. It is classified as soluble or insoluble. Good sources include whole grains, fruits, and vegetables. Some soluble fibres form a gel that slows food movement through the intestines.

Importance of Fibre

1. Facilitates food movement in the alimentary canal, preventing constipation
2. Reduces risk of heart diseases and bowel cancer
3. Lowers cholesterol levels in the blood

Balanced Diet

Balanced diet is a diet containing the correct proportion or the right amount of all the six food substances required by an organism or man. The balanced diet must contain the six food substances such as carbohydrates, proteins, fats and oil, minerals, vitamins and water.

Benefits of a Balanced Diet

• A balanced diet promotes overall health and strengthens the body's resistance to diseases.
• It supports the growth and normal development of the body.
• It provides the energy needed for daily activities.
• A balanced diet helps prevent malnutrition, nutrient deficiencies, and related diseases. For instance, a lack of protein in the diet can lead to kwashiorkor in children, which is characterized by symptoms such as a large head, narrow neck, swollen and shiny stomach, flat buttocks, and thin legs.

Enzymes

An enzyme is a protein that speeds up chemical reactions in the body without being used up or changed Digestive enzymes speed up chemical reactions that break down large food molecules into small molecules.

Characteristics of Enzymes

1. specific in action(Affects only one process/Reaction)
2. protein in nature
3. Required in small quantities
4. Remain chemically unchanged at the end of the reaction
5. Temperature specific. They have a specific temperature range at which they work best with the optimum temperature of 37C
6. affected by pH
7. Most enzyme actions are reversible
8. Some enzymes require Coenzymes
9. Enzymes action can in inhibited by inhibitors

Amylases

Amylases are digestive enzymes that break down carbohydrates (starch and complex sugars) into glucose. Examples include:

• Ptyalin: Breaks down cooked starch into maltose.
• Maltase: Converts maltose into glucose.
• Sucrase: Breaks down sucrose into glucose.
• Lactase: Converts lactose into glucose.

Proteases

Proteases are enzymes that break down proteins into amino acids. Examples of proteases include:

• Pepsin: Breaks down proteins into peptones.
• Rennin: Coagulates milk and converts it into casein.
• Trypsin: Converts proteins into peptones and polypeptides.
• Erepsin: Breaks down peptones and polypeptides into amino acids.

Lipases

Lipases are enzymes that act on fats and oils, converting them into fatty acids and glycerol. An example is:

• Lipase: Breaks down fats and oils into fatty acids and glycerol.

Factors Affecting Enzyme Activity

1. Temperature:
   • Temperature affects the kinetic energy of enzymes, the rate of collisions, and their activity.
   • Enzymes work best within a specific temperature range (optimum temperature), usually between 37°C and 40°C.
   • At very low temperatures, enzyme activity is minimal or absent.
   • Increasing the temperature (up to a certain limit) boosts enzyme activity.
   • If the temperature exceeds the optimum, enzyme activity decreases, and the enzyme may become denatured, making it non-functional.
2. pH (Hydrogen Ion Concentration):
   • pH measures the acidity or alkalinity of a substance.
   • Enzymes are active only within a limited pH range:
   • Trypsin is active in an alkaline medium.
   • Diastase is active in a neutral medium.
   • Pepsin is active in an acidic medium.
3. Enzyme Concentration:
   • Increasing enzyme concentration speeds up the reaction if there is enough substrate available.
   • Once all substrate molecules are bound, the reaction rate will no longer increase as there will be no additional substrate for the enzymes to act on.
4. Substrate Concentration:
   • Increasing substrate concentration increases the reaction rate to a certain point.
   • Once all enzyme molecules are saturated, further increases in substrate concentration will not affect the reaction rate.

Food Tests

Starch Test

Procedures

1. Take a small quantity of the food item and place it on a porcelain tile.
2. Add 2 drops of water to dilute the food.
3. Place 2-3 drops of iodine solution on the food.
4. Observe the color change of the food.

If the food turns blue-black, it indicates the presence of starch in the tested food item.

Protein Test

To determine if a food item contains protein, the Biuret test can be used.

Procedure:

1. Take a clean and dried test tube.
2. Add the food sample into the test tube.
3. Pour in 2ml of sodium hydroxide and add 5 to 6 drops of copper sulfate solution.
4. Gently shake the test tube to mix the ingredients thoroughly, then allow the mixture to stand for 4–5 minutes.

If a violet or purple color appears, it indicates the presence of protein in the food sample.