Veterinary Andrology and Reproductive Techniques

MILK DILUTOR

• Thacker and Almquist (1951) have shown that boiled homogenized milk and boiled pasteurized skim milk are excellent dilutors for bull semen and presented the first of a series of papers on their successful use of heated milk as a semen diluents.
• Boiled, filtered milk gave highly satisfactory results at extension ratios upto 1:25.
• Thacker and Almquist (1953) showed that spermicidal action of unheated milk is associated with albumin containing fraction of milk.
• Flipse et al. (1954) indicated that “Lactenin” an antistreptococcal agent is normally present in milk in its albumin fraction which is toxic to sperm.
• This can be inactivated by heating to 92⁰C for 10 minutes only. Use of whole or skim milk in semen extenders also protects sperm against cold shock.

The milk protein, casein, has been established as the agent responsible for prevention of cold shock.

• Salisbury (1957) has reviewed the use of liquid whole milk, skim milk and powdered milk as bull semen extenders.
• Milk combined with sugar, glycine, glycerol and egg yolk were reviewed.

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• Milk dilutor is prepared as follows:
  • Obtain fresh, homogenized, pasteurized cow’s milk or fresh pasteurized skim milk from the reliable dairy.
  • Using an accurate thermometer, heat the milk to 92 to 95⁰C and hold at this temperature exactly for 10 minutes in the top portion of a covered glass double boiler or in a covered vessel placed directly on a hot plate.
  • Cool the milk to room temperature and remove the fat layer; or milk may be drawn with pipette from its deeper layer by piercing through fat layer.
• Add the following to the above milk
• Suphanilamide - 0.3 gm/ml
• Penicillin G sodium - 1000 units/ml
• Dihydrostreptomycin sulphate - 1000 µg/ml
• The protective fraction of the milk is composed of phospholipids. The toxic fraction of milk (lactenin) is removed with the removal of albumin from milk.
• Michajilov apparently considered that heating process released glucose from the disaccharide, lactose, in the milk, thus providing available carbohydrate substrate for the cells.
• The release of sulpha-hydral (SH) groups from milk by heating process produces an intensely reduced condition, which protect the SH containing enzymes of the spermatozoa and by limiting the available oxygen in storage tubes, forces the cells into anaerobic metabolic activity, which is one important form metabolic control.
• Egg yolk which contains sulpha-hydryl group containing, compounds improves the quality of heated milk as a semen extender.
• A level of 10 to 20% of egg yolk greatly improves the keeping quality of semen. Joshi et al (1967) used heated cow milk for preservation of buffalo semen upto 4 days.
• The use of skim milk dilutors for preserving buffalo semen was reported by Tomar and Desai (1961) and the significant improvement in the efficiency of skim milk medium was observed when egg yolk and glycine or fructose were incorporated in it.
• Kale (1963) also reported successful preservation of buffalo semen by incorporating egg yolk and glucose in boiled milk.
• In skim milk dilutor visibility of sperm was better in comparison to whole milk.
• Jesichen (1965) reported the use of powedered milk extender (Laiciphos) with 10% egg yolk and observed good fertility.
• “Spermasol” is another commercial preparation which has been used successfully.

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