Influence of fasting and refeeding cycles on growth, health and feeding costs of the Amazonian fish Colossoma macropomum

ABSTRACT Feed restriction can be used as a management strategy to increase feed efficiency through compensatory growth (a higher growth rate after a period of restricted feeding). However, there is still a lack of information on the physiological mechanisms underlying the fish responses to feed restriction. Therefore, this study aimed at investigating the cycles of fasting and refeeding on the performance, cost feeding, health and physiological mechanisms of juvenile tambaqui (Colossoma macropomum). For this purpose, feeding protocols were tested for 60 days: continuous feeding (control); two days of fasting and refeeding for two days (F2R2); two days of fasting and refeeding for three days (F2R3) and two days of fasting and refeeding for four days (F2R4), on a total of 108 two-month-old tambaqui juveniles (29.53 ± 1.31 g), distributed in 300 L boxes. Weight gain (g) was lower for the F2R2 and F2R3 treatments compared to the control. Fish subjected to the F2R4 feeding strategy showed similar growth to the group of fish continuously fed. Only the restriction protocol F2R3 resulted in a reduction in blood glucose, while cholesterol was reduced in F2R2 and F2R3. There was mobilization of hepatic glycogen in the F2R3 and F2R4 treatments, while muscle lipids were not altered. The different fasting cycles did not affect leukocyte respiratory activity, hematocrit or hemoglobin. The lowest relative feed cost values were in the F2R2 and F2R4 treatments. The F2R4 protocol reduces feed cost and maintains the ability to adjust energy metabolism without causing stress in C. macropomum.