Physiological responses to long fasting followed by refeeding in juveniles of pirapitinga, Piaractus brachypomus

For many fish species, prolonged fasting is part of their life cycle, as there are seasonal fluctuations in the quantity and quality of food available in their natural habitat. These animals use endogenous reserves during periods of food scarcity and recover when resources become available again. We evaluated the effect of a prolonged fasting period on indicators of body reserve use, growth performance and intestinal integrity of the Amazonian serrasalmid Piaractus brachypomus. We distributed 66 juveniles (68.6 +/- 2.2 g) in 11 tanks. The treatment consisted of 30 days fasting followed by 45 days refeeding and the control of 75 days normal feeding with 5 replicates (one tank with six fish). The six individuals in the 11th tank were used for baseline measurements. Blood parameters, muscle lipid concentration, hepatosomatic and mesenteric fat indices, somatic growth parameters and intestinal villi morphology were measured every 15 days. Glucose, triglycerides, cholesterol, total protein, the mesenteric fat and hepatosomatic indices, weight gain, specific growth rate, condition factor and total biomass decreased significantly during fasting compared to the control, but all except body condition recovered during refeeding. The length and perimeter of the intestinal villi was significantly lower during fasting compared to the control. The feeding protocol allowed P. brachypomus to mobilize part of their body reserves during fasting, however, in general, refeeding was sufficient to restore their body needs and growth performance compatible with that of continuously fed animals.