Nutrition In Animals

Animal Nutrition Animals generally lack the ability to produce their own food and depend either directly or indirectly on plants for sustenance, classifying them as heterotrophs. Animals are categorized into three groups based on their dietary preferences: Carnivores: Feed on flesh or other animals (e.g., lions). Herbivores: Feed on plants (e.g., goats). Omnivores: Feed on […]

Animal Nutrition

Animals generally lack the ability to produce their own food and depend either directly or indirectly on plants for sustenance, classifying them as heterotrophs. Animals are categorized into three groups based on their dietary preferences:

  1. Carnivores: Feed on flesh or other animals (e.g., lions).
  2. Herbivores: Feed on plants (e.g., goats).
  3. Omnivores: Feed on both plants and animals (e.g., humans).


Classes Of Food Substances

Animal nutrition involves seven primary classes of food:

  1. Carbohydrates
  2. Proteins
  3. Fats and oils
  4. Mineral salts
  5. Vitamins
  6. Water
  7. Roughages



Carbohydrates, derived from foods like bread, yam, and rice, consist of carbon, hydrogen, and oxygen. They are classified into three types:

  1. Monosaccharides (Simple sugars): Glucose, fructose, and galactose.
  2. Disaccharides (Reducing sugars): Maltose, sucrose, and lactose.
  3. Polysaccharides (Complex sugars): Starch, cellulose, chitin. Enzymes such as ptyalin, maltase, and lactase break down starch into glucose. Excess carbohydrates are stored as glycogen in muscles and liver.


Importance of Carbohydrates:

  1. Provides energy
  2. Generates heat for maintaining body temperature
  3. Used for lubrication (e.g., mucus)
  4. Supports body framework (e.g., exoskeleton in insects)



Proteins are complex molecules composed of amino acids and include carbon, hydrogen, oxygen, nitrogen, and sometimes phosphorus and sulfur. Protein sources include eggs, meat, fish, and beans. Enzymes like pepsin, rennin, trypsin, and erepsin break down proteins into amino acids.


Importance of Proteins:

  1. Supports growth in young individuals
  2. Repairs worn-out tissues
  3. Produces enzymes and hormones
  4. Supports reproduction
  5. Essential for tissue and organ formation


Fats & Oils (Lipids)

Fats are solid at room temperature, while oils are liquid. They consist of carbon, hydrogen, and a small amount of oxygen. Digestion results in fatty acids and glycerol. Sources include palm oil, groundnut, and soybeans. Lipids are broken down by lipase enzymes.


Importance of Fat and Oil:

  1. Provides more energy than carbohydrates
  2. Supplies essential fatty acids
  3. Helps in maintaining body temperature
  4. Provides fat-soluble vitamins


Mineral Salts

Mineral salts, except for sodium chloride (table salt) and iron tablets, are consumed in small quantities through food. Essential minerals include calcium, magnesium, potassium, phosphorus, sulfur, chlorine, iron, iodine, fluorine, manganese, copper, cobalt, and sodium.


Importance of Mineral Salts:

  1. Regulates body metabolism
  2. Contributes to bone and teeth structure
  3. Aids blood formation
  4. Controls chemical reactions
  5. Supports enzyme and pigment formation



Vitamins are organic substances required in small quantities for normal growth and development. They are grouped into water-soluble (B complex, C) and fat-soluble (A, D, E, K) vitamins.


Vitamins And Their Roles

Vitamins play crucial roles in maintaining overall health and well-being, contributing to various physiological functions within the body. Here is an overview of different vitamins, their sources, functions, and the potential symptoms associated with their deficiency:


Vitamin A:

  1. Sources: Liver, eggs, fish, milk, palm oil, vegetables.
  2. Functions: Supports normal growth and proper vision.
  3. Deficiency Symptoms: Night blindness, reduced resistance to diseases.


Vitamin B1:

  1. Sources: Yeast, milk, beans, groundnut.
  2. Functions: Essential for normal growth, heart, and nervous system function.
  3. Deficiency Symptoms: Beri-beri, paralysis.


Vitamin B2:

  1. Sources: Yeast, soya beans, egg, milk, green vegetables.
  2. Functions: Promotes growth, supports eye function, and co-enzyme formation.
  3. Deficiency Symptoms: Slow growth, dermatitis.


Vitamin B3:

  1. Sources: Yeast, beans, milk, vegetables.
  2. Functions: Facilitates co-enzyme formation for cellular respiration.
  3. Deficiency Symptoms: Pellagra.


Vitamin B12:

  1. Sources: Kidney, liver, fish, milk.
  2. Functions: Crucial for red blood cell formation.
  3. Deficiency Symptoms: Pernicious anemia.


Vitamin C:

  1. Sources: Fresh fruits, green vegetables.
  2. Functions: Aids in wound healing and enhances resistance to infections.
  3. Deficiency Symptoms: Scurvy.


Vitamin D:

  1. Sources: Fish, milk, egg, liver, sunlight.
  2. Functions: Increases absorption of calcium and phosphorus, essential for bone calcification.
  3. Deficiency Symptoms: Rickets, osteomalacia.


Vitamin E:

  1. Sources: Green vegetables, egg, butter, liver.
  2. Functions: Promotes fertility in animals.
  3. Deficiency Symptoms: Sterility, premature abortion.


Vitamin K:

  1. Sources: Fresh green vegetables, liver.
  2. Functions: Supports blood clotting mechanisms.
  3. Deficiency Symptoms: Hemorrhage.


Understanding the sources, functions, and potential deficiencies of these vitamins is crucial for maintaining a balanced and nutritious diet to support optimal health. Incorporating a variety of vitamin-rich foods into one’s diet ensures a well-rounded and comprehensive intake of essential nutrients.



Water, composed of hydrogen and oxygen, is crucial for all organisms. It can be obtained from various sources such as food, rivers, streams, and ponds, constituting 75% of the human body.


Importance Of Water

  1. Facilitates metabolic activities in the body of animals.
  2. Aids in the digestion of food.
  3. Maintains body temperature.
  4. Serves as a medium for transporting nutrients.
  5. Helps in maintaining osmotic balance in body tissues.
  6. Assists in the excretion of metabolic waste, e.g., urine.



Roughages refer to indigestible fibrous materials derived from vegetables, fruits, carbohydrates, and proteins. They play a role in aiding digestion, and their absence can lead to constipation.


Balanced Diet

A balanced diet consists of a correct proportion of all essential food substances. In general, a balanced diet comprises 15% protein, 15% fat and oil, 10% vitamins, minerals, and water, and 60% carbohydrates. Consuming food in these proportions promotes normal growth and development in the body.


Functions Of Balanced Diet

  1. Promotes overall health.
  2. Enhances resistance to diseases.
  3. Provides the necessary energy for biological activities.
  4. Prevents malnutrition and deficiency symptoms. For instance, protein deficiency can lead to a nutritional disease called kwashiorkor in children, characterized by features like retarded growth, weight loss, swollen legs (oedema), and a cracked/split stomach.


Digestive Enzymes

Enzymes, organic catalysts produced by living cells, accelerate or decelerate chemical reactions. Digestive enzymes aid in breaking down complex food substances into simpler, soluble forms. Characteristics of enzymes include:

  1. Solubility
  2. Protein composition
  3. Specificity in actions
  4. Sensitivity to temperature (optimal range: 35°C to 40°C)
  5. pH specificity
  6. Induction of reversible reactions
  7. Dependence on co-enzymes for activation and susceptibility to inhibitors like mercury and cyanide


Classes And Functions Of Enzymes

Digestive enzymes are categorized based on the type of food they act upon:

  1. Proteases (e.g., pepsin, rennin, trypsin, erepsin) – Act on proteins.
  2. Amylases (e.g., ptyalin, lactase, maltase, sucrose) – Act on carbohydrates.
  3. Lipases – Act on lipids (fats and oils).

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