The importance of the degree of semen dilution.
The degree of dilution of the equine semen determines the final concentration of the protective ingredients in the diluted semen. Therefore, it is crucial to have a minimal degree of dilution to get an effective preservation capacity. The following experiment illustrates this.
A semen sample of stallion Fabe was split in 2 parts and diluted at 2 different rates. The image below shows the results.
This experiment shows a moderate difference between the 2 different degrees of dilution. In other cases, the effect can be considerable.
The following images show the results of experiments that show more dramatic differences between two different dilution rate .
The image below shows a dilution of 1 ml ejaculate with 4.5 ml Hippex medium versus dilution of 3 ml ejaculate with 3 ml medium. The ejaculate was from stallion Olgert.
The image below - the third example - shows a dilution of 1.5 ml ejaculate with 4.5 ml Hippex medium versus dilution of 3 ml ejaculate with 3 ml medium. This was done with Hippex and INRA96 for comparison. The ejaculate was from stallion Gjalt.
These experiments shows that to ensure the preservation of equine sperm cells in Hippex extender for more than 2 days, it is recommended to dilute equine semen with at several 3 volumes of Hippex extender. The optimal degree of dilution varies per stallion, but 2.5 volumes of extender is effective for most stallions.
Experiences with Hippex during the past 2 years have shown that the non-centrifugation method is effective when the semen is diluted with at least 3 volumes equal to the volume of the semen. This can be done with good results for over 90% of the stallions. When properly applied, Hippex gives excellent preservation during at least 3 days. After 3 days over 90% of the stallions diluted sperm show more than 50% viability and motility.