Natural feed after weaning improves the reproductive status of Solea senegalensis breeders

The aim of this study was to evaluate the effect of long term natural feeding in the subsequent reproductive status of 4 years old cultured Solea senegalensis, and to determine if the potential changes were structural or feeding dependent. To this aim, two different feeding regimes were used from one year after weaning and during the following 3 years; 1) a commercial dry food diet and 2) a natural feeding regime. After this period, the proportion of fluent males and the evolution of maturity stages of females over a breeding season were studied. A complete sperm quality analysis assessment was carried out, including individual volumes, motility, density and curvilinear, rectilinear and mean velocities of spermatozoa. Moreover, viability and apoptosis indexes were analyzed as indicator of molecular sperm membrane integrity. Additionally, a morphological characterization of the testes during the spawning season was conducted. Finally, both groups were fed with the same commercial pellets during one year to evaluate the effect of the diet of previous years on sperm quality. The results of this study showed how feeding can improve not only sperm quality and quantity, but also the proportion of fluent males and females in advanced maturity stages. All the sperm quality parameters resulted significantly higher in the group fed with a natural diet. Moreover, the number of apoptotic cells was significantly higher in the group fed with a commercial diet. According to the morphological features of the testes, the animals fed with a natural diet presented more basal position, less protuberances and irregular edges when compared with the animals fed with commercial diet. Interestingly, the progression of the spermatogenesis determined by the proportion of germ cells and the production of spermatozoa determined by the wider of the ducts system was also significantly larger in the natural diet group. After the standardization of the diets, mean volume per male and production of total motile cells were significantly higher in the group that was previously fed a natural diet, confirming structural improvements.

Automated summary

The study evaluated the effect of long-term natural feeding on the reproductive status of 4-year-old Solea senegalensis, finding that natural feeding improved sperm quality and quantity, and enhanced the proportion of both male and female fish in advanced maturity stages.