Veterinary Andrology and Reproductive Techniques

EGG YOLK

• When spermatozoa is cooled to 5 ° C they are subjected to cold shock, which causes leakage of intracellular enzymes and other materials present in the spermatozoa.
• This damage can be prevented by providing addition of lecithin, protein, lipoprotein and similar compounds present in the egg yolk.
• In addition the glucose, proteins and vitamins present in the egg are utilized by the spermatozoa and also protect the enzymes and antiagglutinic factors present seminal plasma.
• The value of the yolk of the hen’s egg as a diluting medium in semen preservation was found by Philips during 1939.
• It helped in rapid growth in recent years of artificial insemination throughout the world.

Egg yolk protects lipoprotein sheath of sperm against cold shock.

• The active principle in yolk responsible for this is now thought to be lecithin or a similar phospholipid occurring either free or in combination with protein.
• It contains glucose, proteins, vitamins and required viscosity index which may be of advantage to the sperm cells.
• The hydrogen peroxide formed, which is toxic to the sperm, may be destroyed by additions of the enzyme catalase to the yolk diluents, under anaerobic conditions the problem does not occur.

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Preparation of Egg Yolk

• Egg yolk is commonly added with buffer at the ratio of 1: 4 (20%) to prepare the extender for dilution.
• Unfertilized egg is used for this purpose.
• The egg should be purchase from disease free, known flock.
• Fresh egg immediately after laying is purchased
• The egg immediately after receiving is wiped with dry cotton and stored at refrigerator at 4-5 ° C
• Maximum it can be stored for 3 days at refrigerator temperature of 4-5 ° C
• Immediately before use it is cleaned with swab of 70% alcohol
• It is opened at the narrow end with the help of a sterilized foreceps.
• The white of an egg (albumin) is drained off with the help of an egg yolk separator and yolk is placed on a sterile filter paper.
• If required yolk may be transferred to another filter paper to clear traces of albumin.
• Then the vitelline membrane is punctured with a sterile glass rod and yolk is allowed to fall in a sterilized graduated cylinder directly at the bottom without touching the walls.
• The required quantity is prepared and added with autoclaved buffer (added with glycerol) and mixed with magnetic stirrer.

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