Summary Reader Biology of Domestic Animals

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Summary - Reader Biology of Domestic Animals

  • 1.1.1 Function of the egg

  • Dimensions of animal eggs vary widely between species, this is linked to quantity of the yolk.
  • What is the function of the egg?
    To provide a closed environment and the nutrients for an (bird)embryo to develop.
  • 1.1.2 Egg production

  • What species is mostly used for egg production?
    Chicken mostly but also some ducks and geese
  • What was the first industrial housing system for egg production?
    The battery cage, before this chickens could roam around freely.
  • What housing systems are used now?
    Enriched cages, free-range or aviary barns.
  • 1.1.3 Structure off eggs

  • What does the egg consist of? 4
    -the yolk
    -egg white
    -shell membranes
    -the shell
  • The composition of the egg determines the degree of development in the young emerging from the egg.
  • The smaller the yolk, the less developed the young the emerges is.
  • Egg structure
  • What is the function of the germinal disk?
    ALways faces upwards regardless of te eggs position.
  • 1.1.4 The chemical composition of the egg

  • Egg white consists of water on a very large extent and contains a lower percentage of protein that the yolk.
  • What is the most common protein in the egg white?
    Ovalbium, this lends a firm structure to cakes and custard when used in food.
  • What does the yolk mostly consist of?
    Lipids, saturated fatty acid chains,, phospholipids, cholesterol and proteins.
  • 1.1.5 Quality of eggs

  • Freshness tests:
    1. candling, fresh eggs allow light to pass through it and the yolk is dimly visible.
    2. shaking, in a fresh egg nothing is heard. In an old egg you can hear the insides shaking.
    3. Bowl of salt water, the fresh egg remains at the bottom. The older an egg is the more it stands up in the water.
    4. Fresh egg will have a lot of thick egg white.
  • What characteristics are checked for external egg quality? 3
    1. Size and weight
    2. Shape and appearance, egg shape is determined by the shape index, appearance is the colour and purity of the shell.
    3. Shell strength, is important because almost 7% of the eggs are lost due to breakage.
  • What characteristics are checked for internal egg quality? 3
    1. Yolk colour, depends on customers wishes.
    2. Blood and meat spots, they are found undesirable by the customer.
    3. Quality of egg white, layer of thick white close to the yolk and an edge of thin white further out. Thick white is measure whith Haugh Units.
  • 1.2.1 Formation of the egg

  • A modern laying hen can lay continue to lay eggs without mating or even in the absence of a rooster.
  • What does tthe procustion process for an egg depend on?
    Hormone synchronisation and balances.
  • The hormonal cycle of the hen is under influence of FSH and LH.
  • What does FSH do?
    FSH promotes yolk formation and the growth of the follicles in the ovarium.
  • What does LH do?
    Once a follicle is ripe, the LH ensures ovulation. The ovulation takes place 8-10 hours after release of LH.
  • Steps in egg production:
    1. FSH promotes yolk formation and growth of follicles.
    2. Once a follicle is ripe LH is released.
    3. AFter 8-10 hours ovulation occurs.
    4. Egg enters the funnel(infundibulum) of the egg guide(oviduct)
    5. The oviduct is stimulated by hormones of the ovarium at the appropriate moment to recieve the egg cell.
    6. During the passage through the oviduct the egg cell is surrounded by egg white.
    7. At the end of the oviduct(isthmus), the egg is surrounded by two shell membranes.
    8. Calciums shell is deposited around the egg in the shell gland(uterus).
  • How is egg white formed?
    Egg white is formed by the glands in the wall of the oviduct.
  • Faults in the system often result in abnormal eggs.
  • When do errors in the egg production process mostly occur?
    At the start of the lay with young birds, overstressed hens or as a result of disease or feeding errors.
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How do mammal ingest their food?
With their mouth, teeth and tounge
What do al vitamins have in common?
  • Perfrom essential functions in very small quantities.
  • An animal cannot, or insufficintly synthesise these comounds.
What are the requirements for trace elements in feed?
Ranges from 1-50 mg per kg of dry matter.
What is the requirement for macro elements in feed?
Varies from 10-30 gram per kilo of dry matter.
What are trace/micro elements?
Elements active in the metabolic processes, are present in very samll amount but improtant to good health.
What are macro elements?
Are the building blocks of the body.
What are essential minerals?
Mineals that are needed in animal tissue and from which deficiency leads to deficiency symptoms.
In what form are fats found in animals?
  • Phospholipids in membranes
  • Lipoproteins (cholesterol) in blood
  • Fat globules in milk
  • Intracellular in fat reserves.
In what form are fats found in plants?
In plants fats mainly occur as triaclyglycerols.
What are essential and non-essential fatty acids?
  • Essential: must be included in the feed
  • Non- essential: the body can synthesise these.