Optimising Filtered Egg Yolk Extenders for Long-Term Cold Preservation of Ram Sperm: Effects of Osmolarity and Egg Yolk Concentration.

Cold storage is a preferred method for short-term preservation of ram spermatozoa due to its superior fertility rates compared to cryopreservation. This study aimed to optimise the conditions for ram sperm preservation by evaluating the effects of osmolarity and egg yolk (EY) concentration in a syringe-filtered extender. In part A, semen samples were extended with solutions of varying osmolarities (330, 360, 390 and 420 mOsm/kg water). The 390 mOsm/kg solution demonstrated the best preservation of sperm viability, functional integrity and motility over 96 h of storage. In part B, different EY concentrations (10%, 15%, 20%, 25% and 30%) were assessed at the optimal osmolarity (390 mOsm/kg). A 20% EY concentration provided the most effective protection of sperm DNA, acrosome integrity and membrane functionality. Excessive EY levels (> 20%) negatively impacted sperm viability and induced higher lipid peroxidation. These findings emphasise the importance of balancing osmolarity and EY concentration for efficient cold storage of ram spermatozoa, enhancing the potential success of artificial insemination programs in sheep breeding.