Published on Thu, 09/19/2019 - 12:49pm


  In a recent study (Evans et al., 2019), STgenetics® proved their commitment to gender purity in their sex-sorted product. After analyzing 9,447 calvings between 2016 and 2018, STgenetics® concluded
that their sex-sorted semen with a reported female purity of 91% in the lab resulted in a female calf crop of 90.3% in the field. STgenetics® understands the substantial value of calving a heifer out of a
quality sex-sorted product, which is why they continue to design and implement new techniques and technologies that guarantee a consistent gender purity in their S e x e d U L T R A product.

How are sperm sorted?
STgenetics® has substantially advanced the science of sperm sorting in the past 5 years to improve efficiency, production, fertility, and gender purity. In the first stages of the process, semen is evaluated based on several
quality control parameters. Next, a stain is introduced to the ejaculate which binds to the DNA content in each cell. The sorting technology is based on the content difference between X- and Y- chromosome-bearing sperm which in cattle is about
4%. Genesis™ Digital sperm sorting systems orient sperm in a single file and measure the fluorescence of each of the sperm cells to determine their DNA content when excited by a laser. A charge is then applied to each
droplet based on their DNA content. These droplets are then deflected into tubes collecting X-bearing sperm, Y-bearing sperm, and undetermined, dead, or no sperm.

How is gender purity analyzed?
The Genesis™ Digital sperm sorting systems are verified to confirm that the setup is accurate for the desired sex ratio in the lab by utilizing a Genesis I Analyzer™ to evaluate gender purity before each ejaculate is sorted. The Genesis I
Analyzers™ are calibrated using certified nuclei as a standard to confirm the instrument is aligned and validated prior to purity analysis. Once calibrated, a sample of 3,000 to 5,000 cells is analyzed for gender purity. This calibration
process is a standard procedure in all ST labs to validate that the sperm sorters are operating properly. Several technological developments have contributed to an increased accuracy in gender purity analysis.
STgenetics® has developed a proprietary method for the specific purpose of purity analysis, which provides for better orientation of the sperm, so they can be accurately identified as X or Y bearing sperm. STgenetics® has also
designed an application software specific to sperm purity analysis, which allows for the clear visualization of sperm sub-populations shown in Figure 1A, 1B, and 1C.

STgenetics® diligence in testing their product has proven a reliable formula for producing the desired
heifer crop in the field. In order to verify gender purities in the field, the sex ratios of over 9,000 calvings
from 7 STgenetics® bulls were estimated. The semen originated from 400 individual freezes, for which lab
purities were averaged by bull and compared to the female calf ratio in the field, as depicted in Figure 2. As
the results indicate, the purity analysis in the lab, which averaged 91.1%, yielded on average a 90.3% heifer calf
ratio in the field. These results demonstrate the accuracy of STgenetics’ procedures, which ensure a quality heifer
crop from their SexedULTRA4M™ products.