Protein hydrolysate from cattle residues can be included in diets for Nile tilapia (Oreochromis niloticus) fingerlings

The study aimed to determine the optimal level of inclusion of protein hydrolysate from cattle residues in diets for Nile tilapia fingerlings. Nile tilapias with an average initial weight of 5 g were used, distributed in 15 net cages. The experiment was carried out for 42 days in a completely randomized design with five treatments (0.0%; 2.5%; 5.0%; 7.5% and 10.0% inclusion of protein hydrolysate) and three replications, with that 50 tilapia were stored in each net tank. After the experimental period, the fish were anaesthetized for blood collection and measurements of the parameters of zootechnical performance. Six animals from each experimental unit were euthanized for further bromatological evaluation of the carcass. The zootechnical performance data, the proximate chemical composition of the carcass and blood biochemical parameters were submitted to analysis of variance (α = 0.05), and the Tukey test (α = 0.05) was applied. There were no significant differences between treatments for the parameters of zootechnical performance and proximate chemical composition of the carcass (p > 0.05). As for blood parameters, a significant difference was detected between treatments in alkaline phosphatase activity, calcium and total protein (p