Performance and isotopic composition of 13C and 15N in muscle tissue of Nile tilapia (Oreochromis niloticus) fed with different protein / Desempenho produtivo e composição isotópica de 13C e 15N no tecido muscular de tilápia do Nilo (Oreochromis niloticus) alimentada com diferentes fontes protéicas

Edvânia da Conceição Pontes

Alternative sources of food have been studied in substitution for fishmeal in aquaculture, and it may result in a difference in incorporation of carbon and nitrogen, depending on the nutritional value and availability of the source. Two experiments were designed to quantify the participation of different protein sources in the muscle tissue in juvenile and post larvae through isotopic composition and its influence on growth and body composition. In addition, the apparent digestibility of feedingstuffs containing mixture of C3 and C4 plants has been studied using 13C as tracer. The experiments were conducted in a random design with five treatments and four repetitions. Diets consisted of by four sources of protein ingredients. soybean meal SBM, coconut meal CM, poultry product meal PPM, meal and fish meal FM, composed five different combinations of diets: SBM100 SBM60CM40 SBM60PPM40 SBM60FM40 SBM19CM10FM10PPM11. In the first experiment, it used 200 juveniles with an average weight of 3.4 ± 0.20 g, distributed in 20 vinyl cages. Fish collections were held after being fed the experimental diets for 0, 22, 28, 38, 44, 66 and 88 days. In this assay, it was observed significant difference (P<0.05) for final weight, weight gain, feed conversion, fillet yield, protein efficiency ratio and condition factorHowever, there was no difference between food consumption, weight and content of the fillet profile. For the experiment two, 300 post-larvae, 20 days old and with average weight starting at 0.07 ± 0.020g, were randomly distributed in the five treatments, making each experimental unit with twenty animals. Six fish collections were held at 0, 6, 12, 18, 24 and 30 days. This assay also showed significant difference (P<0.05) for final weight, weight gain, food intake, feed conversion and protein efficiency ratio. It was observed that juvenile and post larvae did reach the isotopic equilibrium of 13C and 15N with their own diets, thus allowing it to be used for estimating the quantification of nitrogen and carbon incorporated into fish tissue, with exception for the SBM60CM40 diet. The higher percentage of nitrogen in the muscle and carcass were obtained by total diets with fish meal SBM60FM40 and poultry product meal SBM60PPM40To test the digestibility of the diets, 2,500 juvenile with average weight 5.0 ± 1.0 g were used for determination of apparent digestibility coefficient ADC, % of source components C3 and C4 contained in the experimental diets. The values of CDA constituents of experimental diets of fingerling showed lower values for source components C3 in respect of C4 origin. The evaluation of stable isotopes of carbon and nitrogen contained in protein ingredients permitted the estimation of contributions among the different sources, which suggests that the intakes of nutrients are related to the higher quality of the diet. It was noted that protein sources when combined can present superior results when used alone in the composition. The contribution of different protein sources in feed of Nile Tilapia, through the natural variation of stable isotopes of carbon and nitrogen, proved promising.

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