Desempenho produtivo e qualidade da carne de tilápias do nilo (oreochromis niloticus) submetidas a dietas suplementadas com arthrospira platensis (spirulina) na fase de terminação

Abstract

It was intended to measure the productive performance, economic viability and the quality of the fillets of Nile tilapia supplemented with different levels of Arthrospira platensis in grow-out phase. The experiment was conducted in randomized blocks design with split-plots in time (slaughter after 30 and 60 days of suplementation), composed for four treatments (T1: 0%; T2: 1%; T3: 3% e T4: 5% de A. platensis) and four repetitions. Were used 480 tilapia (461.39 g), distributed in 16 boxes. The production performance was evaluated through of survival rate (SR), final weight (FW), biomass (BMf), individual weight gain (WG), feed intake (FI), apparent feed conversion (AFC), gutted fish yield (GFY) and the fillet yield (FY) and the biometric hepatosomatic indexes (HI) and the fat viscerosomatic indexes (FVI). The economic viability was verified for partial operating costs (POC), gross revenue (GR), net partial revenue (NPR) and costs incidence (CI). The quality of fillets was verified for centesimal composition, water holding capacity (WHC), cooking loss (CL), shear force, pH, color, fatty acid profile, cholesterol concentration, thiobarbituric acid reactive substances (TBARS) and carbonyl and sulfhydryl groups of the proteins. The data were analyzed for the time effect of supply of diets by analysis of variance, followed by the comparison of averages by Tukey and the others inclusion levels of A. platensis by regression to 5% probability. The FW, WG, BMf, SR, FI, AFC, FY, FVI, moisture, lipids and ashes content, WHC, CL, shear force, lightness, ratio n-6/n-3 and PUFA/SFA, atherogenicity and thrombogenicity indexes, lipid and protein oxidation parameters showed no difference between the supplementation times. The cultivation for 60 days resulted in an elevation of GFY of T1 and muscle protein content of T2, and the reduction of HI of all treatments, pH of T1, a* of T4, b* of T3 and T4, SFA and MUFA of T1 and T2 and cholesterol of T3 fillets. The inclusion of microalgae levels were significant at 60 days for FY, a* and PUFA/SFA, at 30 days for moisture content, CL and trans fatty acids and both periods for POC, CI, NPR and TBARS. The concentrations of n-3 fatty acids were low and the ratios n-6/n-3 and PUFA/SFA of the fillets were similar to those of T1. Although the Arthrospira has characteristics that provide some growth improvement of the animals and the muscular lipid profile and antioxidant action on the lipid and protein fraction of the fillets, generally, these effects were not significant in the productive performance and in the physical-chemical quality and nutritional value of tilapia meats. Many of the parameters evaluated for cyanobacteria treatments were similar to those obtained in the control treatment. In addition, the supplementation of the feed step up too much the expenses of production. Thus, Arthrospira platensis is still an expensive ingredient and the relation cost-benefit was low, its inclusion in levels of 1 to 5% in the Nile tilapia feed at the end stage is not advantageous for the activity.