Farelo de soja certificado orgânico na alimentação de tilápias do Nilo (Oreochromis niloticus)

Abstract

Two experiments were conducted to evaluate the effect of organic soybean meal (FSO) and conventional soybean meal (FSC) on digestibility and performance of Nile tilapia fingerlings. For the digestibility experiment, 90 Nile tilapia with average weight of 184.16 ± 22.79 g, were distributed in six 180-liter conic tanks in a digestibility system, with constant aeration through blower central air and heating water by thermostat. Three diets were prepared, a reference and two test diets. For the preparation of test diets (organic and commercial soybean meal) were used 70% of the basal diet and 30% of the test ingredients inclusion. Chromic oxideIII was used as inert indicator in proportion of 0.1%. Modified Guelph was used to fecal collection method. For the growth performance experiment, 400 Nile tilapia juvenile were used with an average initial weight of 12.7 ± 0.36 g and 9.2 ± 0.30 cm in length,. Fish were entirely randomized into twenty 500-liter fiberglass tanks, with five treatments and four replications. Four diets were formulated with 32% of crude protein (FSO, FSC, FSO + 20% fish meal (FSO+FP), FSC + 20% fish meal (FSC+FP) and a commercial diet with 32% of crude protein (COM)). The average final weight was evaluated, as well as weight gain, average daily gain, final length, survival, apparent feed conversion, condition factor, hepatosomatic index, visceral fat and carcass chemical composition (dry matter, lipids, protein and mineral matter). Hematologic parameters (erythrocyte, hematocrit and hemoglobin); hematimetrics (mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration); and biochemical parameters (cholesterol, triglycerides, albumin and total protein), were analyzed. The apparent digestibility coefficient of protein were 88.24 and 88.10% resulting in 39.91 and 39.87% of digestible protein for FSO and FSC, respectively. The apparent digestibility coefficient of energy was 75.92 and 70.48%, resulting in 3579.46 and 3141.44 kcal/kg of digestible energy for FSO and FSC, respectively, differing from each other by ANOVA test. Fish fed with diet containing FSC+FP showed the best results of final weight, weight gain and daily weight gain. However, the highest carcass levels of crude protein were verified in fish fed with diet containing FSC+FP. As for the blood parameters, fish fed FSO showed better results in comparison to fish fed with other protein sources. The organic soybean meal offered optimal apparent digestibility coefficient and its use in Nile tilapia diets showed satisfactory growth performance and increased protein deposition in the carcass when it included 20% of fishmeal in the diet