ABSTRACT Recent studies have evidenced exogenous enzymes as nutritional tool to elaborate low-polluting aquafeeds. This study aimed to evaluate effects of enzyme complex (EC) on apparent digestibility coefficients (ADC) of energy and nutrients, including amino acids, as well nitrogen (N) and phosphorus (P) loss in pre-growout Nile tilapia (Oreochromis niloticus). Diets without EC (Control) or with EC supplemented at 225 (EC225) or 450 mg/kg diet (EC450) and fed to Nile tilapia (n = 135, 150 ± 20 g) distributed in an entirely randomized design of three treatments and three replicates of 15 fish each. Fish fed diet EC450 showed higher digestibility of energy, protein, amino acids and mineral, and increased digestible energy (DE; +221.25 kcal/kg diet), digestible protein (DP; +10.54 g/kg diet) contents of diets, whereas reduced N (−23.82%) and P (−18.46%) loss relative to fish fed diet control. This study evidenced that EC at 450 mg/kg diet optimizes the ADC of multiple nutrients, including amino acids, and identified its potential to enhance the nutritive value of feeds and elaborate sustainable feeds for Nile tilapia.

RESUMO Estudos recentes têm evidenciado enzimas exógenas como ferramenta nutricional para elaboração de dietas aquáticas pouco poluentes. Este estudo teve como objetivo avaliar os efeitos de um complexo enzimático (CE) nos coeficientes de digestibilidade aparente (CDA) de energia e nutrientes, incluindo aminoácidos, bem como perda de nitrogênio (N) e fósforo (P) em tilápia-do-nilo, Oreochromis niloticus em crescimento. Dietas sem CE (Controle) ou com EC suplementado em 225 (CE225) ou 450 mg/kg dieta (CE450) foram fornecidas para tilápias do Nilo (n = 135, 150 ± 20 g) distribuídas em um desenho inteiramente aleatório de três tratamentos e três repetições de 15 peixes cada. Peixes alimentados com a dieta EC450 apresentaram maior digestibilidade da energia, proteína, aminoácidos e minerais, e aumento nos conteúdos de energia digestível (ED; +221,25 kcal/kg dieta) e proteína digestível (PD; +10,54 g/kg dieta) das dietas, enquanto houve redução na perda de N (−23,82%) e P (−18,46%) em relação aos peixes alimentados com a dieta de controle. Este estudo evidenciou que o CE a 450 mg/kg de dieta otimiza o CDA de múltiplos nutrientes, incluindo aminoácidos e identificou seu potencial para melhorar o valor nutritivo dos alimentos, assim como elaborar dietas sustentáveis para tilápias do Nilo.

ABSTRACT This research was conducted to determine optimal dietary histidine requirement of grow-out Nile tilapia, Oreochromis niloticus, based on muscle development, expression of muscle-growth-related genes, and blood parameters. Fish (n = 288, initial body weight of 64.17±0.53 g) were fed extruded diets with graded levels of histidine (4.23, 5.44, 7.17, 8.91, and 11.57 g kg−1), containing approximately 289 g kg−1 crude protein and 3565 kcal kg−1 digestible energy. The study followed a completely randomized design with five treatments and four replicates each, for 65 days. There was a quadratic effect of dietary histidine on final body weight, feed conversion, and net protein utilization, and the best values were optimized at 8.09, 7.88, and 7.33 g kg−1, respectively. Feed intake, hepatosomatic index, survival, body composition, and blood parameters of total protein, glucose, triglycerides, cholesterol, hematocrit, and hemoglobin were not affected by dietary treatments. Predominance of hypertrophic growth and higher mRNA levels of myogenin and MyoD were observed in fish fed histidine from 5.44 to 11.57 g kg−1 compared with fish fed histidine at 4.23 g kg−1. The mRNA expression of myostatin was not affected by dietary treatments. The dietary requirement of histidine for grow-out Nile tilapia was determined at 8.09 g kg−1, considering growth performance, muscle development, and gene expression responses.

ABSTRACT This study aimed to determine the length-weight relationship and mathematical models to predict dressed and fillet weight and yield and fillet composition of wild traíra, Hoplias malabaricus (Bloch, 1794). A total of 80 marketable-sized fish from 292.28 to 2879.57 g and 32.06 to 61.19 cm were used. The length:weight ratio was estimated using the equation: W = a × L b, in which W is body weight (g) and L is length (cm). The models of dressed and fillet weight and yield and body were elaborated using first-order ( y ^ i = β 0 + β 1 x i ) or second-order ( y ^ i = β 0 + β 1 x i + β 1 x i 2 ) linear regression analyses. The value of slope b in the length:weight ratio was 3.3732 and intercept was 0.0029. The prediction equations obtained for dressed weight, fillet weight, dressed yield, fillet yield, fillet gross energy, moisture, crude protein, crude lipid, and ash were, respectively: y ^ = 0.3244 + 0.9373 W, y ^ = 0.7651 + 0.4181 W, y ^ = 939.8015 + 0.0019 W, y ^ = 420.55170 + 0.0064 W, y ^ = 997.9600 + 0.0630 W, y ^ = 810.6500 − 0.0085 W, y ^ = 184.080 − 0.0111 W, y ^ = 3.1131 + 0.0049 W, and y ^ = 10.6110 + 0.0009 W, in which W is the body weight of fish (g). We demonstrated the possibility of elaborating realistic expressions to describe degutted weight, fillet weight, and fillet composition. However, lower mathematical adjustment was observed to estimate realistic prediction of dressed and fillet yield.

Colliroja, Astyanax fasciatus, is a new aquaculture species, and information on its dietary essential amino acid requirements is lacking. The whole body composition of 120 farmed fish (16.2 ± 8.8 g) was determined to estimate the dietary essential amino acid requirement based on the ideal protein concept ((each essential amino acid/lysine) x100), and the findings were correlated to the whole body essential amino acid content of Nile tilapia Oreochromis niloticus. The dietary essential amino acids, including cysteine and tyrosine, accounted for 5.46, 4.62, 1.16, 3.28, 5.63, 2.01, 2.59, 2.84, 4.66, 3.39, 0.65, and 3.51% of the total protein for lysine, arginine, histidine, isoleucine, leucine, methionine, methionine+tyrosine, phenylalanine, phenylalanine+tyrosine, threonine, tryptophan, and valine, respectively. There were positive linear and high correlations (r = 0.971) between the whole body amino acid profiles of colliroja and Nile tilapia. Thus, the whole body amino acid profile of colliroja might be used to estimate accurately the essential amino acid requirement.

Colirroja, Astyanax fasciatus, es una nueva especie de la acuicultura y no hay información sobre sus requerimentos de aminoácidos esenciales en la dieta. Se determinó la composición corporal de 120 peces de cultivo (16,2 ± 8,8 g) para estimar los requirimientos nutricionales de aminoácidos essenciales en la dieta, incluyendo cistina y tirosina, basada en el concepto de proteína ideal ((cada aminoácido essencial/lisina) x 100) y los resultados se correlacionaron con el perfil corporal de la tilapia del Nilo Oreochromis niloticus. El perfil dietético de aminoácidos essenciales explica el 5,46, 4,62, 1,16, 3,28, 5,63, 2,01, 2,59, 2,.84, 4,66, 3,39, 0.65 y 3,51% de la proteína, respectivamente para lisina, arginina, histidina, isoleucina, leucina, metionina, metionina+cistina, fenilalanina, fenilalanina+tirosina, treonina, triptófano y valina. Hubo una alta correlación lineal positiva (r = 0,971) entre el perfil corporal de aminoácidos de colirroja y el de tilapia del Nilo. Por lo tanto, el perfil corporal de los aminoácidos basado en el concepto de proteína ideal podría ser utilizado para estimar con precisión el requisito de aminoácidos essenciales de colirroja.