Abstract
Abstract This study was conducted to evaluate the comparative cryoprotective effects of whole egg yolk and clarified egg yolk on post thaw sperm quality parameters and to determine the optimum clarified egg yolk inclusion level (10-20%) in semen extenders for Mashona bull semen cryopreservation. It was shown that there was a significant decrease in sperm quality variables following cryopreservation. Semen quality increased with the concentration of clarified egg yolk, indicating a positive relationship between egg yolk LDL concentration and maintenance of in vitro sperm quality. The 20% clarified egg yolk (CEY20) extender treatment gave post-thaw motility, viability and normal morphology values which were comparable to the control (20% whole egg yolk, WEY20). The 10% clarified egg yolk concentration gave the least post-thaw quality values and the greatest proportion of defective spermatozoa. This experiment found no advantage of replacing whole egg yolk with up to 15% clarified egg yolk in Mashona bull semen cryopreservation. However, 20% clarified and 20% whole egg yolk performed similarly in the maintenance of post-thaw sperm motility, viability and normal morphology.
Highlights
Cryopreservation allows long term preservation of gametes for the purpose of conservation or artificial reproduction
Semen quality increased with concentration of clarified egg yolk with the three concentrations differing from each other (P < 0.05) in post-thaw sperm quality for each parameter tested
This indicated a positive relationship between egg yolk low density lipoproteins (LDL) concentration and maintenance of in-vitro sperm quality
Summary
Cryopreservation allows long term preservation of gametes for the purpose of conservation or artificial reproduction. The LDL’s primary protective mechanism is adherence to and stabilisation of the sperm plasma membrane (Andrabi, 2009; Rehman et al, 2013). Another mechanism through which egg yolk protects against cooling injury is that the phospholipids in LDL form a protective film on the sperm surface or replace sperm membrane phospholipids that are lost or damaged during the cryopreservation process (Holt, 2000). It is the phospholipid moiety of the LDL fraction that has cryoprotective effects in egg yolk
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