Fertility Study Leads to Semen Straw Change

Angus cow and calf

Five years ago, GENEX became the first in the A.I. industry to introduce a beef sire fertility ranking model and data collection process called PregCheck™ fertility rankings. Now, to add to our reputation as a fertility leader in the global beef A.I. industry, GENEX is transitioning beef semen to a ¼ cc straw package size.

An extensive research trial performed by GENEX and published in the scientific journal, Theriogenology, shows a 1.5% conception rate advantage to semen packaged in ¼ cc straws compared to semen packaged in ½ cc straws. In addition, the ¼ cc straw package size is already in use around the world for conventional semen and domestically for sexed semen.

As indicated, the main reason for the change is a better-quality product with higher fertility. While each ¼ cc straw will contain the same number of sperm as our current ½ cc straws, the semen will be more concentrated. That is, they will have less extension media, but the same number of sperm cells.

The transition to all ¼ cc straws for GENEX beef semen will occur over time. On December 1, 2019 the production facilities began producing beef semen in ¼ cc straws. However, the existing ½ cc straw inventory on sires will be exhausted before new production in ¼ cc straws will be released. Thus, there will be a transition period where you may receive semen packaged in both ¼ and ½ cc straws depending on the bull.

Why is GENEX switching from the 1/2 to 1/4 cc straws?

Simply put, fertility. Research trials performed by GENEX and published in the scientific journal, Theriogenology, showed a 1.5% conception rate advantage for ¼ cc straws compared to ½ cc straws.

What makes the ¼ cc straw more fertile?

The ¼ cc semen straw has been the global standard for straw package size for several years. The straw will contain the same number of sperm cells as the previous ½ cc straws with less extender. The new straw size allows sperm cell to cool more rapidly and uniformly resulting in improved sperm cell viability.

Is the number of sperm the same in ½ cc and ¼ cc straws?


Yes. The number of sperm packaged in the new ¼ c straw size will be the same amount as was packaged in the ½ cc straw. A ¼ cc straw will contain the same number of sperm and half as much extender.

Can I use the same A.I. gun for ¼ cc straws that I used for ½ cc straws?

Single use ½ cc guns will not work for the ¼ cc straw. A ¼ cc gun or a universal gun, such as the KombiColor gun, is needed for the ¼ cc straws. View the selection of A.I. guns available to USA producers through our e-shop. If you are located outside the USA, please contact your local GENEX retail location or distributor regarding A.I. gun availability.

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