VGO 511: Veterinary Andrology and Reproductive Techniques (1+1)

FACTORS AFFECTING QUALITY OF SEMEN AFTER COLLECTION

Semen which may be of good quality when collected may subsequently deteriorate. Semen of all species are sensitive to environmental and other changes and extreme care should be taken to avoid damage when handling semen

Temperature

• The temperature of semen in most of the domestic animals except for on ejaculation is about that of the body. (37.5⁰ C)
• The exposure of semen to temperature above this increases the metabolic rate, exhausts the energy reserves and decreases the life span of spermatozoa .
• Temperatures above 45⁰ C will kills the spermatozoa
• Reduction temperature will reduce the metabolism of spermatozoa but a sudden drop in temperature , particularly to below 10*c will cause irreversible loss of their viability . motility is not regained on rewarming and fertilizing ability of the spermatozoa is lost. This is called cold shock and can occur through careless over exposure to cold air or by use of cold collecting glass or microscope slide.

Sunlight

• Direct sunlight is detrimental to semen. Short exposure to sunlight may reduce the viability of spermatozoa and 30-40 minutes exposure will kill them. Consequently it is best to avoid exposure of semen to direct sunlight at all times, and all collection and handlig procedures should be carried out indoors and away from shunny windows .
• It’s also wise to avoid prolonged exposure to strong fluorescent lights or UV radiation.

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Contact with metal

• Contact with metal of any kind is harmful to spermatozoa. For this reason only glass utensils or equipment made of inert synthetic materials should be used for collection , dilution and storage of semen and for insemination.

Contact with water

• Water reduces the osmotic pressure of seminal plasma and may there by kill the spermatozoa. Thus water is a powerful spermicidal agent and semen should never be allowed to come into contact with it .
• All equipments should be thoroughly dried before use, including the AV and collecting glasses.

Impurities and bacteria

• Bacteria, dust, hairs, urine and other such contaminants that may get into semen will reduce the viability or kill the spermatozoa .
• Contamination of semen occurs most frequently during collection and can best be avoided by thoroughly cleaning the prepuce of the male before hand.
• After collection the semen should be protected from airborne contaminants by keeping it covered with aluminium foil or a watch glass .
• Aerosol fly – sprays or antiseptics spray should not be used as these too are very harmful to spermatozoa and can persist in the atmosphere for sometime after use
• Proliferation of microbes in the semen can be controlled by addition of antibiotics to the diluents.

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Disinfectants

• Disinfectants and antiseptics are harmful to spermatozoa and their use should be avoided .for sterilization of equipment 70% alchocol in water is suitable but all equipment should be dried before use.

Long exposure to air

• Oxygen in the air increases the metabolic activity of spermatozoa and lactic acid accumulates in the semen . lactic acid may reduce the pH of the semen below the optimum of 7 and the viability of the spermatozoa will be reduced accordingly. Semen shoulde be therefore used for insemination or storage as soon as possible after collection .

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Buffering capacity of dilute

• The media used for dilution of semen should have the capacity to maintain the optimum ph in diluted semen. Shifts in pH either above 7 (alkaline) or below 7 (acid) reduce the viability of spermatozoa.
• The recommended semen diluents contain buffers that is substances able to maintain the medium surrounding the spermatozoa at optimum pH.

Osmotic pressure of diluent

• The components dissolved in the medium surrounding the spermatozoa may exert a pressure on the cell membrane this is known as osmotic pressure, and it increases with the concentration of solute in the medium.
• Media in which concentration of solute is equivalent to that within the cell membrane are said to be isotonic .media with lower solute concentration are hypotonic and those with higher concentration are hypertonic .
• Both hypotonic and hypertonic media are harmful to spermatozoa , there is only a narrow range of tonicity over which a diluent can be altered with out affecting the viability of spermatozoa .spermatozoa remain motile longest when suspended in isotonic diluent .

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