2025/12/03 by Elisabeth Plagnes‐Juan, Maud Martinat, Élodie Baranek +3 · 1 voice
Agricultural and Biological Sciences · Immunology and Microbiology · #Aquaculture Nutrition and Growth #Aquaculture disease management and microbiota #Rabbits: Nutrition, Reproduction, Health
paper · doi:10.1016/j.watbs.2025.100529
openalex created_date 2025/12/03 · openalex publication_date 2025/12/03 · openalex updated_date 2026/07/22
In rainbow trout ( Oncorhynchus mykiss ), early exposure to plant-based diets devoid of fishmeal and fish oil may alter feed intake and affect both nutrient sensing and reward pathways. While homeostatic regulation of feeding is well studied, the potential role of the opioid system in hedonic control during early development remains unexplored. This study investigates, for the first time, the involvement of the opioid system in the regulation of feeding behavior in fry and juveniles fed a plant-based diet (V diet) compared to a conventional diet (C diet) containing fishmeal and fish oil from first feeding to 8 months. Fish were sampled at 5 and 30 Day (fry) and 8 months (juveniles) after feeding initiation. At each age, fish were fasted for 16 h, sampled, re-fed and sampled again at 20 min and 6 h (4 h for juveniles). Expression of opioid receptors ( oprd1 , oprk1 , oprm1 , and ogf1 ) and precursors ( pdyn and penka ) was measured in the whole brain (fry) and telencephalon (juveniles). Gene expression changes were minimal at early stages but became more pronounced at 8 months, particularly in those fed the V diet. Significant differences were observed for pdyn , penka , oprd1 , and oprk1 expression levels, as well as increased serotonin turnover in the V diet group at 30 days and 8 months. Body weight was also lower in the V diet group at all ages. These findings highlight a delayed but diet-dependent modulation of the opioid system, suggesting its involvement in hedonic regulation under plant-based diets in rainbow trout.