The science

The SexedULTRA 4M process

Flow cytometers are used to sort female sperm cells from the male sperm cells. The female (X bearing chromosome) contains 3.8% more DNA than the male (Y bearing chromosome).

It is this difference in DNA content that is detected by the sensors when the sperm cells pass by a laser beam, one at a time in a fluid stream.

A charge is applied to the droplets containing the desired cells and these are subsequently deflected into the required populations of sexed cells resulting in high purity and viability.


On average a Cogent sexed semen straw contains over 90% female semen. The graph shows how this affects the amount of heifers born in 100 calvings compared to conventional semen.

Cogent sexed semen has also been ratified by the world renowned Spallanzani Institute in Italy*. The Spallanzani Institute uses the most accurate form of purity analysis available.

  • Cogent purity analysis = 88% to 97% female
    • Average 91.4% female
  • Spallanzani Institute = 89% to 94% female
    • Average 91.9% female

*Quantification of the sex ratio in sexed bull semen by Real Time PCR. K. Parati, G.Bongioni & A.Galli. Instituto Sperimentale Italiano Lazzero Spallanzani.


Cogent uses more quality control in the semen sexing process than any other stud in the world. In total we use seven tests on the semen; all bar one are post thaw so as to take into account the effects of freezing and thawing on the semen.

These tests include; looking at morphological defects, proportion of dead sperm in the sample, sperm membrane integrity and fertilization ability.


Cogent developed the Harmony Freeze technique in 2002, in an effort to find a gentler, less damaging method of freezing semen.

Harmony Freeze is an incredible process that leaves a significantly higher proportion of live, healthy sperm after thawing than any other commercial freezing method available.

Trials since 2001, on over 2,000 ejaculates, showed that the Harmony Freeze technique resulted in 16% more live semen after thawing than semen thawed using the conventional method.

More live healthy semen means more pregnancies.

Only sexed semen frozen at Cogent is Harmony Frozen.

I have confidence in using Cogent, receiving excellent conception rates and great results time and time again!

James Yeatman Grange Farm, Dorset

Freephone: +44 (0)1829 773400

to speak to one of our representatives