Résumé
Pseudoplatystoma punctifer is a highly appreciated fish species native to the Amazon basin, whose commercial farming has been hampered by low survival during early life stages due to the high incidence of cannibalism and the low acceptability of compound diets at weaning. Dietary DHA is known to promote digestive system development and maturation and growth, whereas its deficiency induces stress. The aim of this study was to evaluate the effect of dietary DHA supplementation on the incidence of cannibalism, digestive physiology, and growth performance during the early life stages of P. punctifer to improve current feeding protocols. Four dietary treatments were generated using a commercial enrichment product with high DHA content. Fish larvae were fed non-enriched or enriched Artemia from 4 to 15 days post fertilization (dpf) and fed a non-enriched or enriched compound diet from 15 to 26 dpf, coinciding with the start of the juvenile stage. Growth, survival, incidence of cannibalism, proximate and fatty acid composition, histology of the intestine and liver, and quantitative gene expression of the main digestive enzymes (amy, try, ctr, pga, pla2, and lpl) were analyzed in the different dietary groups at the end of each feeding period. Results showed that dietary DHA supplementation influenced P. punctifer in a developmental stage-dependent manner. In particular, DHA-enriched Artemia provided during the larval stage contributed to reduce the incidence of cannibalism and improved survival at the early juvenile stage, while enriching the compound diet improved growth. The expression level of genes involved in protein and carbohydrate digestion (ctr, amy) was higher in groups fed enriched Artemia despite that both enriched and non-enriched Artemia displayed similar proximate composition, suggesting that different dietary fatty acid profiles may modulate the expression of these digestive enzyme precursors. The group transitioning from enriched Artemia to non-enriched compound diet showed a higher expression of most genes at the early juvenile stage. At the histological level, the group fed non-enriched Artemia and compound diet showed a significant accumulation of lipids in the intestine relative to the liver, contrary to the rest of the groups that showed similar amounts of lipids in both tissues, indicating a more balanced lipid metabolism. The group fed both DHA-enriched Artemia and compound diet provided the best results in terms of growth, survival, incidence of cannibalism, and digestive physiology. In conclusion, this study showed that the nutritional history during the larval period affected fish nutrition and behavior during the early juvenile stage.