# Early-stage fasting leads to long-term growth inhibition and body composition changes in turbot (Scophthalmus maximus)

## TL;DR

Fasting juvenile turbot early in life causes long-term growth delays and changes in body composition, even after refeeding.

## Contribution

This study shows that early fasting in turbot leads to lasting growth inhibition and body composition changes, challenging the effectiveness of compensatory growth strategies.

## Key findings

- Early fasting for 3 to 12 days caused final growth retardation in turbot, with longer fasting leading to greater inhibition.
- Fasting increased lipid and glycogen accumulation but reduced muscle protein and amino acid content after refeeding.
- Transcriptome analysis revealed that 12-day fasting inhibited protein biosynthesis even after 60 days of refeeding.

## Abstract

Stimulation of compensatory growth by refeeding after a period of fasting has been used as an economical strategy of growth and body composition manipulation in aquaculture practice. In this study, a total of 300 turbot juveniles, at 85 d post hatch with an initial weight of 5.53 ± 0.06 g, were randomly allocated to 15 tanks (20 fish/tank). The control group was continuously fed, while the four experimental groups were subjected to fasting for 3, 6, 9, or 12 d, respectively, followed by a 60-d refeeding. Each feeding strategy was applied to triplicate tanks. Fish were hand-fed a commercial feed (containing 54.0% protein, 8.0% lipid, and 21.6 MJ/kg gross energy) to apparent satiation. Sampling was conducted at the end of refeeding. Early fasting for 3 to 12 d resulted in final growth retardation compared to the control. This growth inhibition was closely correlated to the fasting duration. The 12-d fasting group showed significantly lower (P = 0.027) average weight gain (576%) compared to the control group (709%). Early-stage fasting stimulated the lipid accumulation in various tissues (P < 0.05) and the glycogen accumulation in the muscle of fish after refeeding, but reduced the muscle protein and amino acid content (P < 0.05). The feeding strategy treatments exerted only minor effects on the fatty acid composition of final fish tissues. The transcriptome analysis confirmed that fasting for 12 d in the juvenile stage still inhibited the peptide and protein biosynthesis even after 60 d of refeeding (P < 0.05). In conclusion, compensatory growth through fasting was not observed under the current experimental conditions. Early fasting leads to long-term growth inhibition and changes of body composition in juvenile turbot.