The effect of enriched diets on Solea senegalensis sperm quality

Abstract

Abstract The development of specific broodstock diets could represent an important step toward the obtainment of good quality spawns in the Solea senegalensis. Thus, in the present work we tested the effects of two experimental diets in S. senegalensis males reproductive performance. One broodstock was fed with an experimental diet (Exp1) that, among other components, had a higher docosahexaenoic acid (DHA) content to improve sperm plasma membrane resistance. A second broodstock was fed with the other experimental diet (Exp2), similar to Exp1, but with vitamin E (vitE) and selenium (Se) to control for the increase in the lipid peroxidation caused by the higher proportion of unsaturated fatty acids. In addition, a control broodstock was fed with a diet resembling standard commercial broodstock diets. During the spawning season fish were sampled for blood and semen. Glutathione peroxidase activity, measured as an indirect contribution of Se, was significantly higher in blood plasma of males fed on Exp2 diet. There was a significant improvement in the sperm motility data in the broodstock fed on the Exp2 diet comparatively with the control. Both percentage of progressive spermatozoa and sperm velocity, usually positively related with fertilization rates, were significantly higher in fish fed on Exp2 diet, whereas fish fed on Exp1 did not show any improvement. Sperm plasma membrane integrity before and after motility activation was not affected by the experimental diets. Conversely, lipid peroxidation values (malondialdehyde determination) were significantly higher in sperm of males fed on Exp1 diet. This value was positively correlated with the amount of lysophosphatidyl-choline and sphingomyelin determined by HPLC. There was an increase in cholesterol and in several unsaturated fatty acids in sperm from males fed on Exp2 diet; at the same time, there was a decrease in the amounts of saturated fatty acids, both factors normally associated with improved male reproductive performance. The addition of some PUFA (such as DHA) and antioxidants in Exp2 diet and their synergic effects on the sperm membranes lipidic composition seem to be related with the improved S. senegalensis sperm quality. This study represents a clear step for the design of specific S. senegalensis broodstock diets and the development of this species farming.