Sperm cryotolerance in mature male parr of Atlantic salmon (Salmo salar L. 1758): Effects of dietary lipid content and n-3 essential fatty acids composition

The cryoresistance of sperm is a significant concern issue in conservation and aquaculture. The nutrition of broodstock fish affects the quality of gametes. This study aimed to assess the impact of four diets on the quality of fresh and cryopreserved sperm of sexually mature salmon parr during spermatogenesis. Two dietary factors were modulated: lipid intake (12% and 20%) and n-3 essential fatty acid composition (DHA and ALA). No significant difference in parr growth rate or sperm concentration following the feeding period was observed. Viability and mitochondrial membrane potential of fresh sperm were also unaffected. However, fresh sperm motility was significantly higher in fish fed the 20% ALA diet compared to those fed the 12% DHA diet (p = 0.001). Cryopreservation reduced viability, motility, curvilinear velocity (VCL), and average path velocity (VAP), and increased linearity, regardless of the diet (p < 0.01). However, cryopreserved spermatozoa from parr fed diets enriched with DHA and containing 20% lipids showed a higher percentage of viability compared to spermatozoa from fish fed diets containing 12% lipids (p = 0.044). The study found that mitochondrial membrane potential, motility, VCL, and VAP was higher and that linearity was lower in salmon fed diets with higher levels of lipid and plant-based n-3 fatty acids compared to those fed 12% lipid diets, regardless of the n-3 fatty acid composition. This suggests that the higher levels of lipid and plant-based n-3 fatty acids provided greater resistance of sperm to damage by cryopreservation.