Processing boar semen

The method for processing boar semen influences the outcome of your artificial insemination (AI) program. During processing, sudden temperature changes and exposure to ultraviolet light reduces semen quality.

When handling semen after collection:

• use hygienic techniques (keep all equipment free from dust and dirt)
• treat the samples gently
• maintain a reasonably even room temperature and keep the semen temperature even or at a slow rate of change
• ensure that there is sufficient space in the collection area to lay out all equipment (e.g. storage box, collection flask)
• ensure good lighting and a non-slip surface
• supply facilities for disposal of waste
• wear personal protective equipment
• implement workplace health and safety procedures.

Undiluted fresh boar semen

Effective methods to process undiluted fresh semen for AI programs on most farms include:

• keeping the semen at the temperature collected (34°C)
• using the sample within a few hours of collection
• using 100mL of the gel-free fraction in the insemination process to obtain the best results
• rocking the container gently to disperse the spermatozoa that have settled on the bottom before dividing the sample into doses.

Diluted boar semen

Sometimes it's not practical to use undiluted semen. The use of a diluent will extend its 'shelf-life'.

A simple skim milk diluent protects semen for a few hours, whereas more complex diluents (preferable) allow chilled boar semen to be stored for several days.

For on-farm AI programs, 1 part gel-free semen is added to 4 or 5 parts diluent (e.g. 20mL of good quality semen is made up to 80mL or 100mL with diluent). For higher dilutions, accurate estimates of the total live and normal spermatozoa in the semen sample is needed.

Many commercially available diluents contain an antibiotic which will have a stated withdrawal period. Mated sows cannot be sold for slaughter before the stated withdrawal period for the antibiotic has been met.

The basic steps for diluting boar semen are to:

• dilute only the sperm-rich fractions when storage is to exceed 24 hours (seminal plasma does not protect semen during storage but some inclusion is not detrimental)
• warm the diluent to semen temperature (32–35°C) by standing the diluent in a warm water bath
• gently add the diluent to the semen, not the semen to the diluent (to avoid diluent shock)
• gently agitate the semen before pouring 80–100 mL of diluted semen into the inseminating bottles or bags
• allow semen to cool slowly for 1 hour to around 20°C
• cool semen further (to 14–18°C) over the next hour and store at this temperature range
• gently turn semen containers twice daily to prevent sedimentation.