Avaliação de rações comerciais para juvenis de tilápia do Nilo (Oreochromis niloticus), em tanques-rede

Abstract

The objective of this study was to identify the commercial diets with 32% Crude Protein (CP) that provide the best performance and cost-benefit for fattening of juvenile nile tilapia grown in net tanks. The work was carried out in the fish farming sector of the Agrarian Science Center of the Federal University of Paraíba, from August 26 to October 26, 2016. Sixteen 1m³ tanks were used in an area of 250m². 800 fish were allocated, 50 in each tank-net, at a stocking density of 50 fish / m³. The animals had initial weight and body length of 71 g and 16.1 cm, respectively. The water quality was analyzed throughout the experiment, with the following variables being measured: temperature (ºC), dissolved oxygen (mg / L) and pH three times a week at 8 and 16 hours; And transparency (cm), ammonia (mg / L) and total alkalinity (mg / L), measured weekly. The feed management consisted of commercial diets of four different manufacturers, all with 32% CP, extruded, with pellets of 4 to 6 millimeters, where the animals received daily 4% of the total biomass in feed during the 60 days of the experimental period, subdivided into three daily treatments, at 10, 14 and 16 hours. The chemical composition of the rations was calculated in order to verify if the rations met the guarantee levels proposed on the label. The variables evaluated were survival rate, weight gain and morphometric development. The experiment was evaluated in a randomized complete block design (DBC), with two blocks and two replicates, with four treatments (rations), totaling 16 plots. Therefore, each tank-net was considered a repetition. Statistical analysis of the data was performed by analysis of variance, using the Tukey test at 5% of significance, with the aid of the SAS statistical program. The Treatment 1 remained the one with the lowest weight gain and the one with the lowest gain in length, followed by treatment 2. The Treatments 2, 3 and 4 showed similar weight and length gains. The Treatment 3 presented higher biomass produced. The Treatment 1 presented the worst cost-benefit, followed by treatments 2 and 3, and finally by treatment 4, which presented better cost-benefit. The ration 4 is recommended because it presents the best cost-benefit ratio, providing a good result of weight gain, under the conditions tested, for the fattening of juveniles of nile tilápia created in net tanks.