Freezing of semen

FREEZING OF SEMEN

Freezing the straws in liquid nitrogen vapour (manual freezing)

  • Freezing is carried out in a wide mouthed container (LR 320, LR 250) especially designed for freezing of straws.
  • The actual freezing is done by holding the equilibrated straws at 4.5 cm form the level of liquids nitrogen thereby exposing to the vapours of liquid nitrogen.

When the temperature of semen reaches – 130°C to – 150°C they are transferred to goblets and submerged in liquid nitrogen for storage at – 196 ° C.

  • The main advantage of horizontal freezing is the efficiency and simplicity of the method.
  • The racks hold the straws at a constant level and the straws are frozen at even rate all along the length of the straw.
  • Ensure that the level of liquids nitrogen is 1-2 mm above the safety freezing net.
  • After that the vapour temperature is adjusted by wafting and the racks with straws are kept on the freezing net so that the straws are about 4-5 c.m. form the level of liquid nitrogen.
  • The recommended temperature for freezing semen is LR 320 unit is
  • Medium straws: - 150 ° C to - 160 ° C for 7 minutes.
  • Mini straws : - 120 ° C to - 130 ° C for 9 minutes
  • These containers are used for freezing as well as storage of semen.
  • The maximum storage capacity of LR 250 will be about 70, 000 French medium straws can be stored in 3 layers.
  • With LR 320 one lakh French medium straws stored in 4 layer.
  • The height of canisters to be used for LR 250 and LR 320 containers should be 25 cm and 40 cm respectively.
  • Normally semen banks should plan and store a minimum of 4 months of its supply to the field in advance.

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Freezing in bio freezer (Click here for video demonstrationView video)

  • Where large scale freezing is carried out the freezing is done by using bio freezer.
  • Here the freezing programme is already fed in a computer.
  • It can be altered whenever required. The bio freezer is connected with liquid nitrogen tank and the chamber temperature is brought to +5 ⁰ C.
  • Transfer of freezing rack from cold handling cabinet to freezing unit should be done in the shortest possible time to avoid any increase of semen temperature above +5°C.
  • To achieve this cold handling cabinet and freezing unit is kept in the same lab.
  • The freezing racks are placed inside the bio freezer and it is allowed for 5 minutes to get stabilized at +5 ⁰ C.
  • Then freezing is started. The entire process will take 9 minutes where the temperature will reach from +5 ⁰ C to -140 ⁰ C.

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Last modified: Monday, 11 June 2012, 11:43 AM