Apparent Digestibility Coefficients of Nutrients and Energy from Animal-Origin Proteins for Macrobrachium rosenbergii Juveniles

Abstract

In prawn farming, the main protein source used in aquafeed formulations is fishmeal. Nevertheless, one estimates that in the coming years, this protein source will no longer be able to meet the demand for the activity. The search for new ingredients is important to meet the increasing demand and minimize environmental impacts, such as the reduction in fish stocks and the eutrophication of aquatic systems. The objective of this study was to determine the apparent digestibility coefficients of dry matter (DM), crude protein (CP), gross energy (GE), and ether extract (EE) of fishmeal, poultry co-products (viscera and hydrolysed feather), and insect meal (Gromphadorhina portentosa) for giant river prawn (Macrobrachium rosenbergii) juveniles. To determine the apparent digestibility coefficients (ADCs), 90 prawns (average weight, 15 g) were randomly distributed among three experimental units. The reference feed was formulated according to the requirements of the giant river prawn, with 35% crude protein and a gross energy of 3600 kcal kg−1. The test diets comprised 70% of the reference diet and 30% of the respective test ingredients. Prawns were fed three times a day until apparent satiety. Faeces were collected using the indirect siphoning method, twice a day at the same feeding site (at 7:30 a.m. and 6:30 p.m.). The water parameters were temperature (27 °C), dissolved oxygen (6.65 mg L−1) and pH (7.76). The ACDs of DM, CP, EE, and GE were, respectively, 61.48; 88.28; 99.89 and 88.25 for fishmeal; 76.48; 81.55; 97.29 and 85.13 for poultry viscera meal; 73.82; 75.21; 73.17 and 76.42 for hydrolysed feather meal; and 52.35; 59,48; 87.95 and 67.64 for G. portentosa meal. The values of protein (%) and digestible energy (kcal kg−1) were 55.20 and 3711 for fishmeal; 47.27 and 4285 for poultry viscera’s meal; 65.03 and 4145 for hydrolysed feather meal; and 47.72 and 3616 for G. portentosa meal. These results showed the potential use of insect meals and poultry co-products as ingredients for the diets of M. rosenbergii juveniles, as they present digestible values close to those found for fishmeal, the main raw material used in aquaculture diets.