Compensatory growth and energy metabolism of tambaqui Colossoma macropomum submitted to different periods of food restriction
Author: Bruna Gomes Alho (Currículo Lattes)
Supervisor: Dr Mario Roberto Chim Figueiredo
Abstract
The present study evaluated the effects of food restriction and feedback on growth and energy metabolism of juveniles of tambaqui Colossoma macropomum. The experimental design consisted of 12 tanks with a useful volume of 250 L, with 35 juveniles each (average weight 65.8 ± 12.76 g and average length 11.7 ± 1.06 cm). The fish were divided into four treatments: Continuously fed (control), food deprivation for one (J1), two (J2) and three (J3) weeks, followed by satiety feedback for two weeks. The survival rate was 100% at the end of the experiment. At the end of food deprivation, the body weight of J1, J2 and J3 fish was 77.8%, 70.7% and 48.8% of the body weight of control fish (133.3 g), respectively.The fish from treatment J2 after two weeks of feedback exceeded the body weight of control fish, and J1 reached the same body weight as those continuously fed. However, the J3 fish, in two weeks of feedback, continued to have a lower body weight than the control fish (p <0.05). The condition factor was not affected by treatments or collection periods (restriction and feedback), demonstrating that the fish were in the same body condition throughout the experiment. The hepatosomatic index (IHS) showed a significant difference between treatments (p <0.05), and sampling times. In the refeeding period, the highest IHS averages occurred compared to the food restriction period. Glucose levels varied according to sampling time and between treatments (p <0.05),remaining low in the restriction period, when compared to the feedback period. At the end of the fasting period 7, 14 and 21 days, hepatic glycogen content was almost depleted, but two days after refeeding, hepatic glycogen increased with values similar to the control concentrations. On the other hand, muscle glycogen remained balanced throughout the experimental period, except in fish subjected to three weeks of food deprivation (J3), suggesting the point of hepatic glycogen depletion in group J3, beginning the mobilization of muscle glycogen to supply energy levels and maintain the body's homeostasis. In conclusion, the results obtained show that the tambaqui is capable of showing compensatory growth, if submitted to a maximum of two weeks of fasting,followed by two weeks of feedback.