Veterinary Andrology and Reproductive Techniques

INTRODUCTION

Preparation of semen diluent is a vital step in any semen processing laboratory.

• The function of semen dilution is not only to increase the viability of sperm in vitro for providing nutrients and buffer salts.
• The purpose of diluting semen is to extend its volume so that many females can be bred from a single ejaculate.
• Fluids used for diluting also prolong the life of sperm, provide energy to the sperm and one of the ingredients acts as a so called ‘buffer’.
• The purpose of the buffer is to keep the fluid at the degree of alkalinity necessary to preserve the life of the sperm.
• Such extenders are used to preserve its fertilizing capacities throughout the various procedural stages necessary prior to its proper introduction into the female reproductive tracts at estrus.
• Dilution and preservation of semen is carried out with suitable media, which are non-toxic and provide nutrients for the maintenance of spermatozoa along with egg yolk.

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A satisfactory diluent must have

• Similar osmotic pressure - isotonic to blood, semen and milk (around 275-300 mOsm) and should be capable of maintaining the entire storage period.
• Proper balance of mineral elements which are essential to the life of sperm cells.
• All sperm cell nutrients for both aerobic and anaerobic metabolic processes.
• Lipoproteins and/or lecithin to protect sperm cell against cold shock.
• Chemical means for buffering toxic end products of sperm cell metabolism.
• Antibiotics to inhibit bacterial multiplication.
• Source material to protect from sulphydryl containing enzymes.
• Materials to protect from freezing injuries.
• These are some of the properties of good diluent.

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• Hence, precise weighing of chemicals is absolutely necessary to ensure correct composition. The pH is a good indicator and it should be assessed frequently to ascertain the quality of semen.
• The sperm concentration is determined and the dilution rate is calculated.
• Dilution should be done within 10 minutes after collection. Delaying the dilution adversely affects the semen quality.
• Both the semen and diluent should be at the same temperature (30 ° C) at the time of dilution.
• Semen is diluted with equal quantity of diluent immediately after collection, poured slowly and gently along the sides of the collection tube and then the whole content is emptied into the pre-measured remaining diluent with caution

The death of spermatozoa outside the animal body is due to one of the three following causes

• Destruction of the spermatozoa due to senescence.
• Expenditure of nutritive material
• Autointoxication of metabolic products.

Storage of spermatozoa outside the animal body therefore involves

• Delaying the senescence.
• Slowing down the metabolic processes
• Supply of nutritive materials
• Provision of substances which prevents autointoxication of metabolic products.

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