Compensatory growth and physiological responses of matrinxã (Brycon amazonicus) under cyclic feed restriction

Abstract

This study evaluated the effects of cyclic feed restriction on the compensatory growth and physiological responses of juvenile matrinxã (Brycon amazonicus). A total of 600 fish (~ 12 g) were distributed in a completely randomized design with three feeding strategies: continuous feeding (control), alternate fasting (AF), and continuous fasting (CF) over a 56-day period, divided into two phases: 28 days of restriction (phase 1) and 28 days of refeeding (phase 2). Growth performance, feed conversion, hematological parameters, and biochemical indicators were analyzed. At the end of the experiment, fish subjected to AF and CF achieved full compensatory growth, with final weights similar to the control group. The AF treatment exhibited improved feed efficiency, while the CF treatment required a longer refeeding period to restore growth. During phase 1, fish mobilized lipid reserves, as indicated by reductions in the visceral fat index (VSI) and hepatosomatic index (HSI). Short fasting and refeeding cycles led to changes in hemoglobin values and glucose, triglyceride, and cholesterol levels to maintain the physiological homeostasis of B. amazonicus juveniles, suggesting a low physiological impact of cyclic fasting. However, survival rates were lower in the restricted groups, likely due to increased aggressiveness. These findings indicate that cyclic feed restriction can be a viable strategy to optimize feed efficiency and reduce production costs in B. amazonicus farming, provided that fasting duration is carefully managed. Further research should explore the interaction between feeding protocols, experimental conditions, fish size, and stocking densities to enhance sustainable aquaculture practices for this species.