DIETARY CURCUMIN MODULATES DIGESTIVE CAPACITY AND OXIDATIVE STATUS IN DIFFERENT LARVAE STAGES OF GILTHEAD SEABREAM

Curcumin (diferuloymethane) is a polyphenol extr act from the rhizome of the plant  Curcuma longa and it is known to  possesses a strong antioxidant capacity,  and anti-inflammatory , antimicrobial and immunostimulatory  proprieties. The use of this natural plant extract as a feed additive for juvenile fishes have showed good results as  an  enhancer of growth, oxidative status, stress resistance and promoter of digestion capacity ( e.g., Alagawany et al., 2021). However,  knowledge on  the impact that dietary  curcumin  may have  in early larvae stages is still scare. Marine f ish larvae are  a transitory stage very vulnerable and highly prone to stress that exhibit a drastic metamorphosis involving several morphologic and metabolic changes to achieve the juvenile stage ( Hamre et al., 2013) . Therefore, the aim of this work was to assess if curcumin supplementation  could promote gilthead seabream larvae robustness  and digestive maturation to ultimately improve fish growth performance.

Two experimental trials were conducted to test the effects of different doses of curcumin  (LOW and HIGH) in gilthead seabream larvae and postlarvae.  In Experiment 1,  42  days after hatching (DAH) gilthead postlarvae were fed exclusively  control or  the  supplemented diets for 20 days. At the end of the growth trial fish were sampled to analysed oxidative status, gut maturation, and morphology.  In Experiment 2 , 4 DAH larvae were fed the experimental diets for 27 days, in an early co-feeding regime until 24 DAH .  Diet impact was assessed at several sampling points, to determine the oxidative status, digestive capacity, and feeding incidence of the larvae throughout ontogeny.

 The first trial showed that fish from HIGH and LOW significantly improved the oxidative status compared to CTRL treatment , through a decrease in the content of protein oxidative damage and an increase in the total antioxidant capacity. Moreover, post larvae fed curcumin supplemented diets also presented an upregulation of nfr2 and gr in HIGH and hsp70 in LOW treatments , when compared to  non supplemented fish (CTRL). On the other hand, no differences were observed in the growth performance, intestine morphometry and digestive enzymes activities.

 In the second trial, no differences were observed in growth performance at larvae from 4 to 24 DAH . However, at the end of the experiment (31 DAH) larvae fed LOW diet had a better condition factor than CTRL fish. Moreover, 31 DAH larvae fed HIGH diet showed higher trypsin and chymotrypsin activity levels when compared to CTRL fish. LOW and HIGH larvae were able to  prevent an increase in  the mtROS production during development, in contrast to non supplemented larvae (CTRL).

In conclusion, dietary curcumin supplementation seems to promote larvae digestive capacity and modulate the oxidative status during early ontogeny of gilthead seabream. In fact,  in  postlarvae this supplement  was  able to  enhance  fish oxida tive status through an increas e in the total antioxidant capacity and reduction in the content of protein oxidative damage.  Both studies provide new evidence that dietary supplementation of natural compounds, could be a nutritional strategy to enhance marine fish larvae robustness at  early  life  stages of development.  Therefore,  this study contributes to improve larvae quality production in marine hatcheries and promote a more sustainable industry.

 Acknowledgements

The present study was supported by projects ALG-01-0145-FEDER-029151 “PROLAR – Early metabolic programming in fish through nutritional modulation”, and UIDB/04326/2020 financed by the FCT (Portugal).  Maria J. Xavier was supported by Grant PDE/0023/2013 (SANFEED Doctoral program, with support by FCT and SPAROS Lda ., Portugal).

References

Alagawany , M., Farag, M. R., Abdelnour , S. A., Dawood, M. A., Elnesr , S. S., & Dhama , K. (2020). Curcumin and its different forms: A review on fish nutrition. Aquaculture, 736030.

 Hamre, K., Yúfera, M., Rønnestad, I., Boglione, C., Conceição, L. E., & Izquierdo, M. (2013). Fish larval nutrition and feed formulation: knowledge gaps and bottlenecks for advances in larval rearing. Reviews in Aquaculture, 5, S26-S58.