Thesis defence by Najlae El Kertaoui

Title: Physiological and molecular responses to selected dietary nutrients during early developmental stages of pikeperch Sander lucioperca L.

Pikeperch (Sander lucioperca L.) is recognized as one of the main freshwater species with great potential for the expansion of the EU aquaculture industry. Tailored commercial starter feeds do not exist for this species, and feeds used in hatcheries are mainly developed for marine species. The lack of knowledge on essential nutritional factors has been considered as a bottleneck in new emerging species’ farming, since nutrition is the significant criterium to be considered for economical and sustainable aquaculture. The present thesis focused primarily on the importance of PL and LC-PUFAs’ composition and dietary requirement of Ca/P, as well as their interactions during pikeperch larval development. The multi-nutritional approach allows more precise estimates of nutritional requirements, since the relevant interaction among nutrients are considered. In the course of this thesis, four feeding experiments were carried out using skeletal anomaly incidences, molecular biomarkers and digestive enzymatic activity as main evaluation criteria. Results confirmed the synergistic role of dietary PL and n-3 LC-PUFAs in pikeperch larvae. Dietary PL combined with supplementation of LC -PUFA in the form of TAG resulted in highest growth, lowest incidence of anomalies and improved digestive enzyme activity and had a differential effect on liver proteomics. Essential FA may be directly supplemented as triglycerides to have a beneficial effect on pikeperch larval development. Results further highlighted the major role of Ca/P and EPA+DHA/ARA ratios as well as their interactions with vitamin C during the early post-weaning period. Lordosis and scoliosis seemed to be likely affected by dietary LC-PUFAs, especially DHA. Besides, a strong association is found for the larval tissue amount of ARA and DHA with eicosanoid metabolism, stress response and skeleton anomaly related genes, denoting the effects of dietary LC-PUFAs on immune/stress gene regulation and their potential implication in skeleton development. Interestingly, dietary ARA has probably a sensitive effect on the maturation process (especially the intestinal development) in pikeperch larvae. Results showed that 0.6 Ca/P is efficient to reduce the incidence of kyphosis in pikeperch larvae. Meanwhile, the total P % content should be considered to determine the optimal Ca/P level. This study provided new insights into nutritional requirements of pikeperch larvae and contributed to the development of new pikeperch specific feed.

Najlae will present the results of her PhD thesis, conducted in the Biology Department/URBE under the supervision of Patrick Kestemont.

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ID de réunion : 818 6971 6970
Code secret : 823812