Hippex increases number of motile sperm cells

Introduction.

Previous experiments  with equine semen (but also with rabbit and swine semen) that was diluted in Hippex showed that the storage of the diluted semen resulted in an increase of the number of motile sperm cells ( an increase of about 3-5%).

To analyse this phenomenon in multiple production lots, the production of 8 lots of Hippex for the Spanish military offered an excellent opportunity to gain ample data for statistical analysis.

Experimental setup.

The mother lot was Hippex  53-1407-20-40. Of this lot, there are 8 sub-lots. Of each sub-lot, 2 samples  were taken for testing. The ejaculate used for the analysis was from the Haflinger stallion Sternkönig (kindly provided by Frank Smeltink, Leestensch Hof, Wervershoof, The Netherlands).

To each of 16 tubes of 6 ml volume that contained 4.5 ml Hippex extender at 30 °C, 1.0 ml ejaculate was added.  The resulting sperm cell concentration was 28.5 million/ml.  Immediately after dilution (no centrifugation was applied), the tubes with diluted semen were put in a refrigerator on a rocking table.

The sperm motilities were determined during storage using the CASA system CEROS II. Each sample was tested in duplicate. At least 1000 cells were counted per analysis.

Results.

 

The results of the analyses are given in the figure and videos below.

 

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Discussion.

Previous experiments  with equine semen diluted in Hippex that contains Pronexcell and Lipex indicated unexpectedly that the storage of the diluted semen resulted in an increase of number of motile sperm cells (about 3-5%).

Previous experiments showed that this effect was solely due to the presence of Pronexcell and Lipex that are added as a mixture. This mixture has antibiotic, antifungal, and antioxidative properties due to a.o. lactoferrin and various soy lecithins. However, it is unlikely that these properties are at the basis of the observed increase in number of motile sperm cells. It is more likely that the action of the soy lipid/lecithin mixture in restoring/improving the fluidity of the sperm outer membrane is at the basis of this above-mentioned increase. This activity of certain soy lipids and lecithins has been reported in many scientific papers.

 

The observation by several Hippex users that Hippex shows a higher fertility than other equine extenders might be related to the above-mentioned increase in motility, since there is a strong correlation between motility and fertility. 

(see: Relationships among stallion fertility and semen traits using estimated breeding values of German Warmblood stallions

Gottschalk, Maren et al. Theriogenology , Volume 89 , 68 - 71)