Straw method


  • The straw method was introduced by scientist of Denmark during 1940 for packing of liquid semen.
  • Adler (1960) first frozen the semen packed in straws by using liquid nitrogen vapour.
  • This technique was later modified by Cassou in 1965 which was called as “medium straws”.
  • This was in use for a period of time. Later Cassou in 1968 brought further improvement by reducing diameter for better freezing which is called as “mini straws”.
  • Most of the straws recently used were called as “French straws” - made of poly vinyl chloride.

The semen straws are made of poly vinyl chloride.

  • Later in German, Simmet (1972) introduced a new straw called “mini tube” or “German straws” or “Landshut system”.
  • Both the ends of this straw was sealed with either steel, glass or plastic beads.
  • For insemination, special sheath is required by which the ball and minitube can be retained in the sheath allowing only the semen to enter the uterus.
  • Another straw known as “Continental straws” made of polypropylene was developed in United States.

The dimensions of French and German straws are as follows


Type of straw





French medium

135 mm

2.8 mm

0.5 ml


French mini

135 mm

2.0 mm

0.25 ml


German straw

65 mm

2.8 mm

0.25 ml

  • The French straws have two ends – factory seal end and laboratory seal end. In this the factory seal end was formed in the manufacturers themselves.
  • The laboratory seal end will be open when it is purchased. The laboratory seal has to be created in the semen processing laboratory after filling the straw with diluted semen before freezing.
  • For creating laboratory seal earlier the poly vinyl alcohol was used. Recently by using filling and sealing machine, after filling by pressing the straw mechanically the laboratory seal is created.

  • Factory seal has two cotton plugs with PVA powder in-between them. This seal is formed by while manufacuring semen straw at factory.
  • Laboratory seal - formed with PVA powder or sealing machine after filling of semen. This seal is formed at semen processing laboratoty.


Advantages of straw method

  • Semen is processed as thin film with its greater surface area to volume ratio. Here there is rapid exchange and better revival rate.
  • Reduced volume of the semen is better tolerated by uterus
  • The diameter of the artificial insemination gun is small so it is easy to pass it through cervix when it is in heat.
  • Complete delivery of semen into uterus is ensured.
  • Identification is easy by using different color straws, different color poly vinyl alcohol powder for different breeds
  • Details like Bull name/No., Breed, Date of collection/batch No. Name of semen bank, first or second ejaculate and other details if required can be printed on the straw.
  • Use of steel gun is safety when compared to glass catheter.
  • The disposable plastic sheath used to cover the AI gun can prevent the disease transmission.
  • Straws occupies less storage space when compared to ampoules
  • Since the straws is handled with automatic machines the hygiene is ensured


Last modified: Monday, 4 June 2012, 11:22 AM