Dietary Probiotic in production systems of Nile tilapia: effect on growth, balance of N and P nutrient retention and economic viability

The objectives were estimate the balance of N and P, the retention of K, Ca, Mg, Cu, Fe, Mn, Zn, Cd, Pb and Cr, and the economic viability in a culture system of Nile tilapia subjected to the addition of B. subtilis and B. cereus in the diet. The analysis of nutrients in the diet and in the fish were carry out for the calculations of the rate of nutrient retention efficiency (RNRE), protein efficiency ratio (PER) and efficiency of nitrogen retention (NER). The experimental design for the content of nutrients in the soil on collection times and collection site at the end of cultivation was in factorial 4 x 2 with five replications and to the NER, and PER in fish RNRE was completely randomized with four treatments and five replicates. The analyses of variance were employed, followed by Tukey test (p<0.05) and regression analysis. The addition of probiotics in the diet influenced (p<0.05) only the efficiency of retention of Mn. The PER it was lower (p<0.05) for the addition of isolated B. subtilis (0.89%) in comparison with feed and B. cereus (1.12%) and free of probiotic food (1.11%). The average values of N, Cu, Mn and Cr were higher in the sediment of the collection box and P concentrations were higher (p<0.05) in the soil. The nutrients N, P, Cu and Fe had a significant increase (p<0.05) in the soil and sediment of ponds of the culture. The diet added to B. subtilis provides worse results of PER and lower NER results in production of large-scale tilapia. The cultivation leads to retention of nitrogen and phosphorus in the soil and sediment collection box. This effect can be minimized in accordance with the increase of ERN and the rate of phosphorus retention efficiency (RPRE) in fish.