ABSTRACT The use of alternative feeds aims to maintain productivity and reduce animal production costs. This objective of this study was to determine the nutritional value of peanut meal (PNM), as well as replacement of soybean meal (SBM) by PNM in diets for Nile tilapia, Oreochromis niloticus. To determine the apparent digestibility coefficients (ADC) of nutrients from the PNM, 40 fish (100 ± 4.3 g) were randomly distributed in four 250 L tanks and fed reference and test diets (50% PNM) plus 0.1% chromic oxide. Feces were collected by modified Guelph system. For the growth performance trial, 180 fish (13.4 ± 0.2 g) were randomly distributed in 30 200 L tanks and fed during 90 days with isoproteic (26.8% digestible protein) and isoenergetic (17.6 kJ g-1 digestible energy) diets containing replacement levels of 0, 25, 50, 75 and 100% of SBM digestible protein by PNM digestible protein. The experimental design was completely randomized with five treatments and six replicates. The ADC for protein from PNM was 90.9% whereas the ADCs for essential amino acids ranged from 88.7% for lysine to 97.6% for arginine. The feed conversion ratio was significantly affected when the SBM was totally replaced by PNM. The protein efficiency ratio, protein retention and whole-body protein content significantly decreased in fish fed diets containing PNM levels above 25% of PNM. Therefore, PNM can replace up to 25% of SBM without impairing juvenile Nile tilapia growth performance, feed efficiency, and body composition.

Resumo: O objetivo deste trabalho foi avaliar os componentes da dieta - fibra bruta, fibra em detergente neutro, fibra em detergente ácido, hemicelulose, celulose e lignina - como indicadores internos na determinação dos coeficientes de digestibilidade aparente da matéria seca, da energia bruta e dos nutrientes - proteína bruta, fósforo e aminoácidos - em tilápia-do-nilo (Oreochromis niloticus). Grupos de dez juvenis (80,3±1 g) foram aleatoriamente distribuídos em seis tanques de 250 L e alimentados com duas dietas práticas, ou com ingredientes de origem vegetal ou de origem vegetal e animal. Ambas as dietas foram suplementadas com 0,1% de óxido de cromo-III (Cr2O3). As fezes foram coletadas pelo sistema Guelph modificado. Os coeficientes de digestibilidade aparente foram determinados pela diferença de teor dos indicadores internos, presentes nas dietas e nas fezes, e comparados, pelo teste de Dunnett, aos obtidos pelo uso de Cr2O3. A celulose foi efetiva na determinação dos coeficientes de digestibilidade aparente da matéria seca, da energia e dos nutrientes de ambas as dietas; e a fibra em detergente ácido foi efetiva apenas para a dieta que continha exclusivamente ingredientes de origem vegetal. A utilização de fibra bruta, fibra em detergente neutro, hemicelulose e lignina, como indicadores de digestibilidade, mostrou-se ineficiente quanto aos nutrientes analisados de ambas as dietas. Assim, a celulose é o indicador mais apropriado para a avaliação de digestibilidade em tilápia-do-nilo.

Abstract: The objective of this work was to evaluate the diet components - crude fiber, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, and lignin - as internal indicators in the determination of the apparent digestibility coefficients of dry matter, gross energy, and of the nutrients - crude protein, phosphorus, and amino acids - in Nile tilapia (Oreochromis niloticus). Groups of ten juveniles (80.3±1 g) were randomly distributed in six tanks of 250 L and fed two practical diets, either of a plant-origin diet or of a plant- and animal-origin diet. Both diets were supplemented with 0.1% chromium (III) oxide (Cr2O3). Faeces were collected by the modified Guelph system. The apparent digestibility coefficients were determined by the content difference of the internal indicators, present in the diets and faeces, and compared by Dunnett’s test to those obtained by the use of Cr2O3. Cellulose was effective in the determination of the apparent digestibility of dry matter, energy, and nutrients of both experimental diets; and the acid detergent fiber was effective only for the diet composed exclusively of plant-origin ingredients. The use of crude fiber, neutral detergent fiber, hemicellulose, and lignin as digestibility indicators was inefficient for the analyzed nutrients of both diets. Therefore, cellulose is the most suitable indicator for digestibility evaluation in Nile tilapia.