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Summary - Reader Biology of Domestic Animals
1.1.1 Function of the egg
fanimal 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.
housingsystems are used now?Enriched cages, free-rangeor aviary barns.
1.1.3 Structure off eggs
What does the egg consist of? 4-the yolk
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.
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
consistsof water on a very large extent and contains a lower percentage of proteinthat 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
Freshnesstests: candling, fresh eggs allow light to pass through it and the yolkis dimly visible.
- shaking, in a fresh egg nothing is heard. In an old egg you can hear the
- Bowl of salt water, the fresh egg remains at the bottom. The older an egg is the more it stands up in the water.
- Fresh egg will have a lot of thick egg white.
What characteristics are checked for external egg quality? 31.
Shapeand appearance, egg shape is determined by the shape index, appearance is the colour and purity of the shell.
Shell strength, is important because almost 7% of the eggs are lost due to breakage.
What characteristics are checked for internal egg quality? 31. 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
matingor 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 o
f FSHand 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:
FSHpromotes yolkformation and growth of follicles.
- Once a follicle is ripe
- AFter 8-10 hours
- Egg enters the
funnel(infundibulum) of the egg guide(oviduct)
oviductis stimulated by hormonesof the ovariumat the appropriate moment to recieve the egg cell.
- During the passage through the
oviductthe egg cell is surrounded by egg white.
- At the end of the
oviduct( isthmus), the egg is surrounded by two shellmembranes.
- 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
oftenresult in abnormal eggs.
errorsin the egg production process mostly occur?At the start of the lay with young birds, overstressed hensor as a result of disease or feeding errors.
Latest added flashcards
- Perfrom essential functions in very small quantities.
- An animal cannot, or insufficintly synthesise these comounds.
- Phospholipids in membranes
- Lipoproteins (cholesterol) in blood
- Fat globules in milk
- Intracellular in fat reserves.
- Essential: must be included in the feed
- Non- essential: the body can synthesise these.