Food and Feeding

 Food supplies the animal with energy for all animal activities.  To provide the materials for growth and repair of cells  To provide materials for production of hormones and enzymes.  To provide raw materials for milk, egg and wool production etc.

 The six most common elements found in food are Carbon (C), Hydrogen (H), Nitrogen (N) Oxygen (O), Phosphorous (P) and Sulphur (S).  The elements found in dissolved salts include Sodium (Na), Magnesium (Mg), Chlorine (Cl), Potassium (K) and Calcium (Ca).  Trace elements are required in our body in very small amounts and include Iron (Fe), Copper (Cu) and Zinc (Zn).  These elements, when combined in different ratios form larger units called biomolecules.

 There are five main food groups:  Carbohydrates  Lipids (Fats and Oils)  Protein  Vitamins  Minerals  Water is often considered the sixth food group, due to the huge importance it plays in our bodies.

 Green plants can make their own food in a process known as PHOTOSYNTHESIS.  Therefore plants are known as autotrophs or autotrophic.  Animals have to ingest their food and cannot make all their food needs.  Animals are known as heterotrophs or heterotrophic.

 The food pyramid is a diagram illustrating which proportions of food types are required in our everyday diet.  Complex Carbohydrates (Starch and Fibre) are the most important.  While fats and sugars are to be taken in the least amount.  The diagram is shown on the next slide.

 The main sources of carbohydrates in our diet are starches and sugars.  Carbohydrates are made up of Carbon, Hydrogen and Oxygen molecules with the common formula C x (H 2 O) x  Carbohydrates are classified by their number of sugar units, called saccharides.  Monosaccharides (1 sugar unit), Disaccharides (2) or Polysaccharides (many).

 Are glucose, fructose and galactose.  All have the formula C 6 H 12 O 6 but arranged differently.  Sources of monosaccharides are energy drinks, but indirectly through all other sugars.

 Contain two sugar units:  Maltose = Glucose + Glucose  Lactose = Glucose + Galactose  Sucrose = Glucose + Fructose

 Starches, Cellulose, Chitin and glycogen etc.  Humans cannot digest cellulose.  However cattle and horses (and other ruminants) can, by a symbiotic relationship with bacteria in their stomachs.  While monosaccharides and di-saccharides provide energy for our bodies, polysaccharides are mainly structural.

Benedicts or Fehlings solution is added to the food sample (dissolved if necessary) and placed in a water bath. A brick red colour is a positive result.

Iodine solution is used to test for starch A blue / black colour is a positive result.

 The main sources are lean meat, egg white, fish, milk, pulse and nuts.  Contain the elements Carbon, Hydrogen, Oxygen and Nitrogen (sometimes Sulphur)  Proteins are made up of units called amino acids.  There are over 80 known amino acids, but only 26 occur in proteins.

 These amino acids form long chains which come together as a protein molecule.  A typical Protein molecule has 500+ amino acids  Some amino acids can be made by our body and these are called non – essential amino acids.  Other amino acids can only be brought into our bodies by ingestion.  These are known as essential amino acids.

 There are no essential amino acids for ruminants.  Proteins are used in the body for growth and repair of cells.  The Biuret Reagent is used to test for the presence of protein in a food sample.  A lilac colour indicates a positive result.

 Sources of fats are obvious – butter, oils, nuts, milk and general fatty foods.  Contain the elements Carbon, Hydrogen and Oxygen but not in any given ratio unlike Carbohydrates.  A unit of fat (called a triglyceride) is made up of one molecule of Glycerol with three fatty acids chemically attached.

 Fats provide energy to the body (twice as much as carbohydrates), insulation and contain vitamins (known as Fat Soluble).  Phospholipids are oil like substances but contain a phosphate group instead of one fatty acid.  Phospholipids are important as they form cell membranes.

 Fats can be known as saturated or unsaturated.  Saturated means that as many Hydrogen atoms as possible are attached to the Carbon atoms.  Saturated fats are usually solid at room temperature and are related to heart disease.  Unsaturated fats contain fewer Hydrogen atoms, and contain what are known as double or triple bonds.  They are usually oil at room temperature.

 Vitamins have many functions in the body.  Vitamins mainly act as co-enzymes, which means they trigger enzymes to work.  Vitamins can be water soluble or fat soluble.  Vitamin C (A water soluble vitamin)  Found in Citrus Fruits  Involved in the absorption of Iron & Respiration  Lack of Vit. C causes Scurvy!!  Vitamin A (A fat soluble vitamin)  Found in the carotene pigment (found in carrots).  Involved in formation of the visual pigments.  Lack of Vit. A causes night blindness.

Minerals have no energy value but are used in the body for many different reasons Osmo-regulation (control of water levels) Acid – Base balance (pH balance) Formation of enzymes, pigments and hormones. Triggers or activators in different reactions. Iron for Haemoglobin in Blood (Anaemia)

 Water has no energy value but again is essential for all bodily functions  Our bodies are made up of 75% water.  Waters main function is as a medium where other food items are stored and moved.  Of course our blood is made of nearly all water so it is vital that the human body gets 3 – 4 pints of water a day.

 Carbohydrates:  Cellulose as a component of Cell Walls  Protein:  Fibrous proteins like Keratin are found in hair and nails.  Myosin is found in muscles.  Lipids:  Phospholipids are a major component of cell membranes.

 Enzymes are biological catalysts.  They are natural substances, which speed up the breakdown of food substances and other materials.  They work by combining with the substrate forming the enzymes – substrate complex.  The enzymes – substrate complex breaks down and forms the product and releases the enzyme.  The enzyme can then be used again.  Enzymes are very specific and will only work on one substrate.  Enzymes are very important in the breakdown of food in our digestive system.  Enzymes work at specific pH’s. Most at pH 7 but pepsin works only at pH 2 & 3.