This study investigates the effect of digestible protein levels in experimental diets for meagre (Argyrosomus regius). A group of 253 fish, 52 g of mean weight, was distributed in 12 tanks, three replicates per treatment. Four isolipidic diets (170 g kg−1 crude lipid) with different digestible protein levels (350 g kg−1, 430 g kg−1, 490 g kg−1 and 530 g kg−1) were formulated using commercial ingredients. The trial lasted 62 days. Meagre fed diets 430, 490 and 530 g kg−1 obtained higher TGC (2.47, 2.57, 2.69 × 10−3, respectively) than fish fed diet 350 g kg−1 (2.14 × 10−3). Group of fish fed diet with 350 g kg−1 DP showed the lowest ammonia excretion level. According to the in vitro digestibility trial diets with 350 and 430 g kg−1 DP released less amino acids in comparison with diet with 49% DP, although in vivo digestibility test did not show significant differences among diets 430, 490 and 530 g kg−1 DP. Using the quadratic regression, optimal digestible protein intake according to the ECR for rearing juvenile meagre was recorded in 0.8 g DP/100 g fish and day.

The meagre is a carnivorous species and might be a suitable candidate species for the diversification of aquaculture in the Mediterranean region. This is based on its high growth and flesh quality. Nevertheless, there is little information available about its growth rates and nutrient requirements. The objective of this study was to determine the protein and energy requirements of juvenile meagre (Argyrosomus regius). Two trials for different weights of 53 and 188 g were conducted with rations from starvation to apparent satiation with the scope of studying its nutritional needs. In the first trial, the initial mean body weight of the fish was 53 g, and they were fed at feeding rates, measured as a percentage of the body weight, of 0, 0.75, 1.5, 2.5, 3.5, and 4.5%, with two replicates per treatment. In a second trial, another group with approximately 188 g of initial body weight was fed at feeding rates of 0, 0.5, 1.5, and 2.5%, with two replicates per treatment. The optimum thermal growth coefficient was obtained with a feed intake of 2.2% day−1 in trial A and 1.73% day−1 in trial B. The digestible protein (DP) intake for maintenance was determined as 0.57 g kg−0.7 day−1, the DP intake for maximum growth was 6.0 g kg−0.7 day−1, and the point for maximum efficiency in protein retention was 1.8 g kg−0.7 day−1. The requirement for digestible energy (DE) intake for maintenance was recorded at 25.4 kJ kg−0.82 day−1, the DE intake to maximize growth was 365 kJ kg−0.82 day−1, and the point for maximum efficiency in energy retention occurs with a digestible energy intake of 93 kJ kg−0.82 day−1. The requirements and retention efficiency of protein and energy in Argyrosomus regius tend to be within the range other fish species. The maintenance needs are in agreement with species with low voluntary activity and growth requirements in agreement with fast-growth species.

Las muestras de animales plagas fueron colectadas, secadas y molidas. Estas fueron analizadas para determinar su contenido en proteína, cenizas y aminoácidos. Los análisis bromatológicos mostraron que Achatina fulica y Pieris brassica, contienen más proteína bruta, (PB) (779.2 y 812.2 g/kg) en comparación a Phyllophaga spp. y Spodoptera frugierda (432. 5 y 445.7 g/kg). Comparando el perfil de aminoácidos, A. fulica y P. brassica obtuvieron los niveles más altos en la mayoría de los amino ácidos esenciales (AAE) que la torta de soya y en el caso de A. fulica, éste exhibió valores más altos que la harina de pescado en arginina, cisteina, glicina, serina y tirosina. Observando la relación de AAE/AANE (amino ácidos no esenciales) en las harinas, sólo S. frugiperda presentó valores similares a la harina de pescado (0.85). Todas las harinas de animales plagas presentaron una reducción en la cuantificación de amino ácidos en relación con los valores de PB obtenidos por el método de Kjeldahl, esta reducción se encontraba entre 28.6 y 38.0%. Esta disminución podría deberse a la combinación entre la proteína y la quitina que se encuentran en el cuerpo de los insectos. A pesar de esta reducción la cuantificación de amino ácidos de los animales plagas podría ser una buena alternativa para su uso en la alimentación de monogástricos, especialmente para peces y crustáceos.