Effects of diet on sperm functionality and cryopreservation tolerance in Atlantic salmon (Salmo salar)

This study evaluates the impact of dietary composition on the functionality and cryopreservation tolerance of intratesticular spermatozoa in Atlantic salmon (Salmo salar). A total of 40 males were divided into four dietary treatment groups: Diet I, based on marine-derived lipids and proteins; Diet II, replacing 65 % of marine proteins and 51 % of lipids with plant and terrestrial animal sources; and two commercial reference diets (III and IV) to contrast with the experimental diets. Over a six-month period, dietary treatments influenced critical sperm quality parameters such as motility, membrane integrity, oxidative stress markers, and cryopreservation outcomes as assessed in both fresh and cryopreserved samples using biomarkers of cellular function, mitochondrial membrane potential, and DNA integrity. Sperm in Diet 1 had the highest motility (80.6 ± 5.7 % fresh; 68.4 ± 8.7 % cryopreserved) and showed reduced oxidative damage, with lower levels of lipid peroxidation (3.8 ± 0.9 nmol MDA/mL) and 8-OHdG concentrations (0.7 ± 0.4 ng/mL). Conversely, sperm from Diets III and IV exhibited higher oxidative stress and DNA fragmentation, which were associated with reduced post-thaw viability. The results underscore the critical role of dietary polyunsaturated fatty acids (PUFAs), such as DHA and EPA, in maintaining sperm membrane fluidity, motility, and resistance to cryopreservation. Diet II exhibited intermediate performance, indicating that partial substitution of marine ingredients can be viable if lipid composition is carefully balanced. These findings emphasize the importance of dietary formulation in aquaculture for optimizing sperm quality and cryopreservation tolerance, contributing to sustainable reproduction strategies for Atlantic salmon and other high-value species.