Effects of cyclical short-term fasting and refeeding on juvenile Lophiosilurus alexandri, a carnivorous Neotropical catfish

Abstract

The effects of different feeding strategies on the growth rate and hematology of Lophiosilurus alexandri were investigated. An experiment was carried out at the Laboratório de Aquacultura, Universidade Federal Minas Gerais, with nine hundred juvenile L. alexandri (length 4.3 ± 0.3, weight cm 0.9 ± 0.2 g) fed exclusively extruded dry diet and kept in fifteen 30-L cultivation tanks in a recirculating aquaculture system. The design was completely randomized with five replicates of each of three feeding treatments: every day of the week (control), six days of the week (F6:1) and five days of the week (F5:2). The following were calculated at the end of the experiment: survival, daily weight gain (DWG), total length (TL), daily feed intake (DFI), feed conversion rate (FCR), specific growth rate (SGR), final body weight (FBW), condition factor (K), protein efficiency ratio (PER), nitrogen retention (NR) and the hepatosomatic index (HSI). Blood samples were taken after 42 days (prior to feed restriction) and at 45 days (after feed restriction of one or two days), and levels of hematocrit, total plasma, hemoglobin, erythrocytes, leukocytes glucose, cholesterol and triglycerides determined. Data were submitted to ANOVA and means compared by the Tukey test (5%). No significant differences were found for survival, FCR, DWG, TL, FBW, K, and SGR. The highest DFI and HSI values were recorded in the control treatment, while PER and NR were highest in the F5.2 treatment. The highest hematocrit values were observed for the control and F6:1 treatments. In all treatments, the values for hematocrit, total protein, leukocytes and glucose were lower after fasting. The highest values for leukocytes were for the control and F6.1 treatments prior to fasting, while after fasting the control treatment was highest. For the F5:2 treatment, the highest value for erythrocytes was after fasting. The highest values for cholesterol were after fasting for all treatments. In conclusion, L. alexandri exhibits compensatory growth in relation to the two short-term food restriction treatments tested. The species adapted to dietary strategies and maintained hematological and biochemical parameters close to those of the control groups when returned to feeding.