Replacement of fish meal with soybean meal in diets for Mugil platanus: studies on growth, body composition and economic viability
Author: Leonardo Rocha Vidal Ramos (Currículo Lattes)
Supervisor: Dr Mario Roberto Chim Figueiredo
Fishmeal is an increasingly limiting resource in the formulation of food for aquaculture, mainly because of the price, variable quality and availability on the market. Therefore, it is necessary to study other sources of food to make aquaculture a more sustainable activity. The aim of this study was to evaluate soybean meal as an alternative to fishmeal for juveniles of the mullet Mugil platanus. The experimental design consisted of 12 tanks (310L) with a useful volume of 200L, with 30 juveniles each (average weight 0.59 ± 0.17 g, average length 30.26 ± 3.27 mm). Four isoproteic (35% CP) and isocaloric (3,600 Kcal / kg) diets were formulated, in triplicates. One ration was formulated without soy and three others with increasing levels of substitution (0, 25%, 50% and 75%) of fish meal for soybean meal.The experiment lasted 50 days. The physical and chemical parameters of the water (temperature, dissolved oxygen, pH and salinity) were taken daily, always in the morning. Biometrics were performed every 10 days and, at the end of the experiment, the fish were collected and euthanized for analysis of the proximal composition. Survival, weight gain (GP), apparent feed conversion (CAA), specific growth rate (TBI), condition factor (K), protein efficiency rate (TEP), economic conversion rate (CEc) were evaluated , viscerosomatic (IVS) and hepatosomatic (IHS) indexes. There were no significant differences (P> 0.05) for the physical and chemical variables of the water. There was no statistical difference in any of the performance variables analyzed (p> 0.05). There was a significant difference (P <0,05) for CEc and for the moisture and lipid content of fish. The statistical analysis (P> 0.05) of the hepatosomatic and viscerosomatic indexes did not show significant differences. Soybean meal is a less cost-effective and more widely available ingredient in the food market than fishmeal. On the other hand, the result of the present study indicates that the replacement of fish meal at the level of 75% by soybean meal does not pose risks to the production of the studied species Mugil platanus.