Ração amazônica para tambaqui: uma tecnologia social para aquicultura familiar

Abstract

The cassava and fishing chains are well-established in Amazonas State, and its residues can be used as feed ingredients. In addition to these residues, in the Amazon, it is possible to raise and use larvae of the black soldier fly (BSF, Hermetia illucens) as a protein ingredient. This study evaluated the potential of diets for tambaquis, Colossoma macropomum, using Amazonian ingredients. Diets were formulated containing cassava by-products: crueira, leaves and shoots, as a source of starch, fiber and energy, in equal proportions in each diet. Fish meal (FM) and defatted BSF meal (BSF) were used as protein ingredients. Five diets containing different increasing levels of FM replacement by BSF (0%, 25%, 50%, 75% and 100%) were formulated. A conventionally formulated diet (CD) was used as a control. Tambaqui juveniles (24.61 ± 1.14g) were housed in 24 tanks (150 L; n=4; 20 fish/tank) in a water recirculation system. Tambaquis were fed 4 times a day until apparent satiation for 60 days. At the end of the experiment, all fish were weighed and blood was collected from 3 fish/tank for hematological analysis. Three fish/tank were euthanized to obtain biometric indices and centesimal composition of the whole body fish. Parametric data were compared by one-way analysis of variance and, when significant, by Dunn's test, with each treatment compared individually with the control treatment (commercial diet, CD). Non-parametric data were analyzed using the Kruskal-Wallis test and the Dwass-Steel-Critchlow-Fligner (DSCF) mean contrast test. Data from treatments 0 to 100BSF were submitted to regression analysis. No refusal of pellets or mortality was observed during the experimental period. Fish fed diets containing cassava by-products showed similar apparent feed conversion (FCR=1.76) and protein efficiency rate (PER=2.02%), regardless of the level of replacement of FM by BSF. However, these values were lower than those observed by the group of fish fed the CD (FCR=1.33, PER=2.67%). No differences were observed in the centesimal composition of the whole body composition and in the biometric indices. Fish fed diets formulated with BSF had similar cholesterol levels, however worse than fish fed 100% FM (0BSF), probably due to the chitin present in BSF. Fish fillets fed with Amazonian feed showed a higher rate of yellowing, which may be related to the carotenoids present in the cassava leaf. The use of defatted BSF meal and by-products from the cassava production chain can promote the sustainability of Amazonian aquaculture, however further studies are needed to improve the formulation of the Amazonian feed to provide better production rates in tambaqui farming.