The effect of extender on the Motility and Progressive Motility of caprine semen.
Danni Louie
XCell Genetics, November 2023
Introduction:
The role of semen extender in cryopreservation of caprine semen is to protect sperm from harmful events during the freezing and defrosting processes. A quality extender helps decrease freezing and osmotic shock, cell injury by ice crystal formation as well as reducing oxidative stress on sperm cells. There are multiple commercially available semen extenders on the market. For this experiment three different extenders, one egg based (Bovine-EXT one part by Reproduction Resources (Egg)) and two synthetic based, (AndroMed CSS one step by Minitube (CSS)) (OptiXcell 2 by imv Techologies (OPT)) were utilized and post thaw motility and progressive motility were analyzed.
The dilution of goat semen with diluents, which contain egg yolk or skimmed milk, can have a detrimental effect on the quality and fertilizing capacity of cryopreserved spermatozoa. Goats are apparently unique among domestic livestock species in secreting semen-specific lipase enzymes that can interact with egg yolk lipids or skim milk triglycerides, therefore, generating products that are toxic to sperm cells (Blanka, 2018). Synthetic extenders could help reduce this reaction and increase motility of goat semen.
Motility of semen has long been known to play an important role in the conception rates of AI breeding in goats. The higher the post thaw motility the better quality the semen is considered. With proper AI procedures, caprine semen put up at a concentration of 120 m/ml (60 million per 0.5 ml straw) and having a 50% post-thaw motility yields suitable fertilization rates (Dr. Louis C. Nuti). This essentially means that 30 million mobile sperm cells are considered the minimum level required for satisfactory semen quality.
Not as much information is known about progressive motility acceptable ranges in caprine semen. To obtain an accurate progressive motility rating, a program is needed that analyzes the velocity and straightness of the path the sperm is swimming. The progressive motility is considered the lowest number of sperm represented in the sample that can produce pregnancies. Equine and bovine processors want the progressive motility to be higher than 20% with many processors setting the cut off levels at 30% on semen with concentrations 165 m/ml or higher. The Merk Veterinary Manual states that for a bull to pass a breeding soundness exam his fresh ejaculate must have a progressive motility of 30% or higher. With this knowledge it could be assumed that quality goat semen would also have a progressive motility of 30% or higher and certainly not lower than 20%. However, more research is needed in goats to determine at what rate of progressive motility conceptions rates start to be affected. What is known is that the higher the progressive motility the higher quality the semen is considered.
Method:
For this experiment semen samples were collected on six different dairy goat bucks, three of the Nubian breed and three of the Saanen breed. Ejaculates were split and added to three different extenders. The collection process, cooling process and freezing process were performed universally across all samples with the XCell Genetics cryopreservation technique. Post thaw results were analyzed with iSperm technology. For every buck three straws of semen from each extender were analyzed. For each straw of semen three iSperm analysis were ran and the average motility and progressive motility were calculated for each straw of semen. Progressive motility was defined as an Average Path Velocity (VAP) of 50 um/s and a straightness (STR) of 75%. The three straw average motility and progressive motility were used to calculate the bucks individual average motility and progressive motility for each type of extender. An average post thaw motility and progressive motility were calculated for each extender from the six induvial bucks’ averages. Average post thaw motility and progressive motility, standard deviations, and P values were calculated using an Excel spreadsheet.
Results:
As shown in Figure 1, there was no difference in post thaw motility for the egg extender and OPT extender (P=0.55). A lower post thaw motility was seen with the CSS extender when compared to the Egg and OPT extenders (P=0.015).
As shown in Figure 2, the OPT extender had a higher post thaw progressive motility than the egg extender and the CSS extender (P=0.015). A lower post thaw progressive motility was seen with the CSS extender when compared to the Egg and OPT extenders (P=0.004).
Conclusion:
Higher post thaw semen motility was seen on samples that were processed with both the Egg and OPT extenders. The highest post thaw semen progressive motility was seen in semen samples that were processed with OPT extender, followed by the Egg extender and the CSS extender having the lowest. This confirms that OptiXcell 2 extender by imv Technologies produces the highest quality of semen with XCell Genetics’ cryopreservation technique.
References:
Blanka Premrov Bajuk , Tina Pihlar , Nina Pogačnik , Primož Klinc, Dialysis of the goat semen and its effect on the quality of frozen/thawed spermatozoa processed in the presence of egg yolk. Animal Reproduction Science. Volume 198, November 2018, Pages 65-73
Louis C. Nuti. Goat Semen Collection and Processing Collection Manuel
Sylvia J. Bedford-Guaus, DVM, PhD, DACT. Breeding Soundness Examination of Bulls. Merck Veterinary Manual. Nov 2023