Scrotal Size EBVs are estimates of the genetic differences between animals in scrotal circumference at 400 days of age. Scrotal Size EBVs are expressed in centimetres (cm) and are calculated from scrotal circumference measurements taken on bulls between 300 and 700 days of age.

The scrotal circumference of a bull provides an important indication of his genetic merit for several important fertility traits. Increased scrotal circumference is associated with earlier age at puberty, increased semen production and improved semen quality.

There is also evidence that increased scrotal circumference is associated with improved female fertility and earlier age at puberty in a bull’s daughters.

How do I record scrotal circumference information?

Scrotal circumference measurements should be recorded by pulling the testes firmly down into the lower part of the scrotum and placing a measuring tape around the widest point (as per diagram). Scrotal circumference measurements can be taken by anyone. They do not need to be taken by an accredited technician.

Measurements should be recorded in centimetres (to one decimal place).

When measuring scrotal circumference, it is important to remember:

• While measuring techniques vary slightly, it is important to use a consistent technique for a whole group of bulls.
• The tension applied to the measuring tape should be just enough to cause a slight indentation in the skin of the scrotum.
• Avoid placing the thumb of the hand holding the neck of the scrotum between the cords. This will cause separation of the testes and an inaccurate measurement.
• A variety of scrotal circumference measuring devices are commercially available from agricultural supply stores or online. Self-tensioning scrotal measurement tapes, such as the Reliabull tape, are recommended as these ensure that the same tension will be applied for each scrotal circumference measurement.

What considerations should be made when recording scrotal circumference information for BREEDPLAN?

• BREEDPLAN can analyse scrotal circumference information from bulls that are between 300 – 700 days of age when measured. Therefore, it is recommended that you measure scrotal circumference when the bulls are reaching puberty, which will vary according to seasonal conditions and the maturity pattern of your cattle. In most cases, scrotal circumference should be recorded when bulls are being weighed at 400 days.
• While more than one scrotal circumference measurement can be recorded for an individual animal, BREEDPLAN is only analysing the first measurement for each bull at this stage. Therefore, it is only necessary to record one scrotal circumference measurement on each bull.

How do I submit scrotal circumference information?

Scrotal circumference information can be submitted to your BREEDPLAN processing centre using any of the following methods:

• The BREEDPLAN paper performance recording forms (forms can be requested by contacting staff at your BREEDPLAN processing centre).
• The BREEDPLAN compatible Microsoft Excel template (available to download in the Help Centre on the BREEDPLAN website).
• A BREEDPLAN compatible herd recording computer program.
• The web services area offered on some breed society websites.

Please see the Methods of Submitting Data to BREEDPLAN tip sheet, available in the Help Centre on the BREEDPLAN website, for further information.

For more information regarding how to record scrotal circumference information or Scrotal Size EBVs in general, please contact staff at your BREEDPLAN processing centre.