Three kinds of blood meal coming from different processing conditions (spray-dried, drum-dried and vat-dried blood meals) were evaluated. Protein extraction and fractionation were performed in each blood meal type to determine the molecular weight profile, which was compared with standard bovine blood in natura. In vitro digestibility analyses of the protein in the diets were carried out in samples, which underwent defattening process or not. The apparent digestibility coefficients of the blood meal in vivo nutrients was determined with the creation of four diets; one of them did not have blood meal, called purified reference diet. For this stage, Nile-tilapia juveniles, with 100.00±5.0 g/fish of average weight were stocked in tanks of 250 liters in a completely randomized blocks design with four replicates and 10 fish per experimental unit. The test diets were obtained with the introduction of 30% of the blood meals in the study. The protein structure of the blood in natura is affected by high temperature and length of time of processing, resulting in an increase in the amount of low molecular weight peptides, and free amino acids, corresponding to low values of blood meal protein digestibility, both in- vivo and in-vitro tests. Spray-dried blood meal and drum-dried blood meal are efficiently used by the Nile-tilapia. In the regular blood meal, protein has lower value than the two other blood meal types. At the development of diets containing blood meal for Nile-tilapia, isoleucine must be the first limiting amino acid, followed by methionine + cystine, arginine, and threonine, which were found in critical levels for this specie, mainly in the conventional blood meal.
amino acids; blood meal; degradation; digestibility; Oreochromis niloticus; protein
