Estimating dietary protein, energy, and amino acid requirements of European catfish (Silurus glanis Linnaeus, 1758) across different growth stages using a bioenergetic approach

There is a lack of information about the nutritional requirements of European catfish ( Silurus glanis ) for aquaculture. This study aimed to fill this gap using a bioenergetic factorial model. To develop the model, a series of sub-studies were carried out. Accordingly, the growth potential of fish was determined using the data collected in this study and from the literature. The whole-body moisture, protein, lipid, ash, and energy content changes were analyzed to reveal how they vary as size increased up to 4000 g. An experiment was conducted to determine the maintenance requirements and utilization efficiencies for digestible protein (DP) and digestible energy (DE). The maintenance requirements of DP and DE were estimated as 0.163 g/kg 0.7 /day and 16.44 kJ/kg 0.8 /day and their utilization efficiencies were 51.72% and 52.52% respectively. Another sub-model for estimating digestible essential amino acid requirements was also run based on the ideal protein concept (IPC) of the European catfish fillet amino acid profile. Each sub-model was then combined to estimate the daily requirements of DP, DE, DP:DE ratio, and amino acids across different sizes of fish. The estimations of DP:DE ratio requirements were converted to dietary specifications for different stages of fish growing from 10 g to 4000 g using a sequential application of two-breakpoint models, which yielded 5 different diets during the farming period of European catfish. The whole model suggested that European catfish require high dietary protein during the early stages, which can be reduced over the culture period by increasing DE. Based on the IPC, dietary digestible essential amino acid requirements were estimated depending on the sizes and diet specifications. This study provides valuable information about dietary DP, DE, DP/DE ratio, and digestible amino acid requirements of European catfish, which requires future validation through controlled feeding trials.