Evaluation of Soy Lecithin Efficacy in Comparison with Egg Yolk on Freezing of Epididymal Sperm in Dogs

BACKGROUND: Epididymal sperm collection is allowed the use of genetic material post-mortem or after orchiectomy from high-value animals or endangered species. OBJECTIVES: The aim of this study was to improve the accessibility of the dog epididymal sperm cryopreservation system based on the appropriate dose of lecithin. METHODS: Epididymal sperm from castrated testes of mature healthy dogs in veterinary centers were collected and divided into six groups: G1: egg yolk 20% (control), G2: lecithin 0.4% (L0.4), G3: lecithin 0.8% (L0.8), G4: lecithin 1.2% (L1.2), G5: lecithin 1.6% (L1.6), and G6: lecithin 2% (L2). Evaluation of Spermatozoa was done before freezing by Motility test, Eosin- Nigrosin vital staining and Hypo-Osmotic Swelling Test (HOST) and after thawing by Computer Assisted Semen Analysis (CASA), HOST, Eosin-Nigrosin vital staining, Mitochondrial Membrane Potential (MMP) and Intracellular Reactive Oxygen Species (ROS). RESULTS: In frozen samples, total motility and proportion of sperm with intact plasma membrane integrity based on the HOS test were lesser in all groups treated with different concentrations of lecithin as compared with the control group (P ≤ 0.05). However, beat cross frequency (BCF) was higher in all groups treated with different concentrations of lecithin as compared with the control group (P ≤ 0.05). Yet progressive motility, the proportion of live sperm based on the Eosin- Nigrosin test, VAP, VSL, VCL, STR, LIN, and ALH did not differ among various experimental groups (P > 0.05). The proportion of sperm with morphological defects did not differ between fresh and frozen samples and among various experimental groups (P > 0.05). Mitochondrial membrane potential was greater in the control than 0.4% lecithin group (P = 0.026). The proportion of sperm positive for ROS was lesser in the control than 0.4% lecithin group (P = 0.049). CONCLUSIONS: egg yolk was superior to the lecithin-based extenders to cryopreserve epididymal sperm of dogs.