Animal Nutrition (Food Substances) – Classes of food, vitamins and minerals

Food is a complex energy-rich organic matter which living organism feed on to obtain nutrients and substances necessary for life. Food substances are classified to six groups

(i) Carbohydrate     (ii) Protein       (iii) Fat and oils    (iv)  Mineral salts  (v) Vitamins     (vi) Water and roughages.

Carbohydrates are made up of carbon, hydrogen and oxygen. They have general formula (CxH2O)y. carbohydrate consists of simple sugar, starches, cellulose and glycogen. They are grouped into simple sugar or monosaccharide, double sugar/disaccharides and poly saccharide. The common sources include yam, cassava, potatoes, bread, cereals e.g. rice, maize e.t.c.

Simple sugar or Monosaccharide

These are the simplest sugar which consists of one molecule of simple sugars. They have general formula C6H10O6. Examples are glucose, fructose and ribose (C5H10O5) or galactose

Disaccharide/Reducing sugar

These are sugars which consist of two molecules of simple sugar which formed by condensation with the general formula C12H22O11. Examples are sucrose, maltose and lactose

Sucrose: It is a non-reducing sugar which is formed from a molecule of glucose and a molecule of glucose is the main source

Maltose: This is obtained from the condensation of two molecules of simple sugar. It is reducing sugar

Lactose (milk-sugar): It is a reducing sugar. It is obtained from the condensation of a molecule of glucose and a molecule of galactose


These are complex carbohydrates. Examples are starch, cellulose, chitin and inulin.

  1. Starch: It has the formula C6H10O5)n where n represent a large number. It is formed from the condensation of numerous molecules of simple sugar. Examples of the sources of starch are yam, cereals, cassava and bread
  2. Cellulose: This is composed of several condensed unit of monosaccharides. It makes the cell wall of plant source of cellulose include whole meal bread, cereals, fresh fruit and vegetables.

iii.       Glycogen (Animal starch): This is the form which animals store their carbohydrate usually in the muscle or liver

Importance of Carbohydrate

  1. It provides energy required by animals for their daily activities
  2. It provides heat during it oxidation used in maintain the body temperature

iii.       It forms certain body part of arthropods (exoskeleton)

  1. The mucus which is an important lubricant in the body is formed carbohydrate


Proteins are complex molecules and are made of smaller unit called amino acids. Proteins have to be digested to amino acids before they are absorbed in the body of animal. The breakdown of proteins during digestion takes place in the following

Protein     —->              Peptone     —->              Polypeptide —->  Amino acid

Protein is composed of carbon, hydrogen, oxygen, phosphorus and sulphur

Sources of protein include both animal source and plant source

The animal source includes milk, egg, fish, cheese, meat and chicken while the Plant sources are beans, groundnut, soya beans and melon.

Importance of Protein

  1. Protein is needed for growth of young ones
  2. It is used for the repair of worn out tissues or cells

iii.       It aids reproduction

  1. It is used for the production of enzymes
  2. It is needed for the production of hormone
  3. It is needed for body building57


Fat and oils are also called lipids. They consist of only carbon, hydrogen and oxygen. However, the amount of oxygen in each lipid is very little e.g. tristearin, is C57H10O6. Fats are solid lipid at room temperature. Plant sources of oil include groundnut, palm oil, soya beans oil; coconut oil and melon oil white animal sources of fat include butter, fish or cod oil.

Fat and oil are hydrolysed during digestion to fatty acid and glycerol

Importance of Fat and Oil

  1. Fat and oil provides more energy to animal than carbohydrate
  2. Fat supplies essential fatty acid to animal

iii.       Fat and oil act as solvent for fat soluble vitamins

  1. They help in the maintenance of body temperature
  2. They act as insulator to animal which help them to conserve heat


Mineral salts are food substances that are required in traces for vital body process. They are taken in their ionic forms. Animal takes in their elements mainly by feeding on plants or their products except a few of them such as sodium chloride (table salt). Lack of mineral salts will result in nutritional deficiency. These mineral elements or salts include phosphorus, calcium, iodine, manganese, fluorine, copper and cobalt.

CALCIUMMilk, Cheese, Egg and Fish(i) Bone and teeth formation and development(ii) Needed for blood clotting(iii) Normal Functioning of the heart, nervous system and muscle(i) Rickets(ii) Osteomalacia(iii) Tooth decay
PHOSPHORUSMilk, cheese, egg, fish and wheat(i) For strong development of teeth and bone(ii) It forms part of DNA and RNA(iii) Needed for respirationi)   Rickets(ii) Osteomalacia(iii) Tooth decay
MAGNESSIUMGreen, vegetables, milk, meat(i) For muscle contraction(ii) Needed for utilization of iron(iii) Needed for teeth and boneNervous disorder
POTASSIUMFruits and other Natural food(i) Needed for functioning of the muscles(ii) For transmission of impulses in nervesIt leads to muscle paralysis
SULPHURBeans, fish, meat & eggConstituent of proteins, amino acids and vitamin BPoor growth
SODIUM & CHLORINETable salt, fish fruit(i) Transmission of impulses(ii) Maintenance of osmotic balance of the cell (i) Dehydration(ii) Muscle cramp
IRONEggs, liver, kidneys, beans, vegetables(i) Formation of haemoglobin in red blood cellAnaemia 
IODINESea foods(i) Required by the thyroid gland to make thyroxine Goitre
MARGANESEEgg, Milk, Meat(i) Required for normal growth(ii) Acts as co-factors in some enzymatic reactions 
COPPERGreen vegetables, eggs, milk, meat(i) It catalyses the use of iron(ii) For proper respiration in some aerobic organismsAnaemia


Vitamins are organic food substances which are needed in small quantities or traces for body normal growth and healthy development in man and other animals. Absence or insufficiency of vitamin supply in diet may lead to deficiency diseases

Groups of Vitamins

(i)         Fat Soluble Vitamins: These are vitamins that are soluble only in fat e.g. vitamins A,D, E and K

(ii)        Water Soluble Vitamins: These are vitamins that are soluble in water e.g. vitamins B-complex and vitamin C. some members of vitamin B2(Riboflavin),  B3 (Niacin), b5 (Pantothenic) B6 (Pyridoxine), B12, (cyanocobalamine), Folic acid e.t.c.

VITAMIN A(Retino)Liver, eggs, fish, milk, palm oil, fresh vegetables(i) Required for normal growth of cells and skin(ii) For proper vision of the eye(i) Night blindness(ii) Reduced resistance to diseases
VITAMIN B1Yeast, unpolished rice, milk, beans, palm wine(i) Required for normal growth(ii) Formation of co-enzymes involved in cellular respiration(i) Slow growth(ii)  Dermatitis
VITAMIN B2Yeast, soya beans, egg, milk, green vegetables(i) Required for growth healthy skin and proper functioning of the eyes(ii) Formation or co-enzymes involved in cellular respiration(i) Slow growth(ii) Dermatitis
VITAMIN B3Yeast, beans, milk, palm wine, yam, vegetablesNeeded for cellular respirationPellagra ( a skin disease and digestive problem
VITAMIN B12Kidney, liver, fish, milkFormation of red blood cellsPernicious anaemia
VITAMIN C(Ascorbic acid)Fresh fruits e.g. Orange and green vegetables(i) Aids wound healing(ii) Helps to resist infectionScurvy (characteristic by bleeding gum, poor healing of wood an low resistance of infection)
VITAMIN DCalciferolFish, milk, egg, liver, form in the skin by lightNeeded for strong bone and teeth formation and developmentRicket, osteomalacia
(Ergo sterol)
Green vegetable, butter, liverPromotion of fertility in animalsReproductive failure e.g. sterility and pre mature abortion
VITAMIN KPhylloquinoneFresh green vegetable/cabbage spinachAids blood clothingHaemorrhage


Water is composed of two elements hydrogen and oxygen. Source of water available to animals include metabolic water from food, drinking water from rivers, rain, pond e.t.c.

Importance of Water

(i)         It is required for metabolic activities in the body

(ii)        Water is necessary for digestion of food

(iii)       It can be used for maintenance of body temperature

(iv)       It is served as a medium of transportation of nutrients

(v)        It helps in excretion of metabolic waste products from the body e.g. urine

(vi)       It is the basis of body secretion from endocrine gland

(vii)      It helps in the maintenance of the osmotic content of the body

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