Resumo:
The present study aimed to evaluate the isolated effects and the interaction between different levels of dietary energy and supplementation with chromium chelated to methionine (Cr-met, Availa®Cr) on the productive performance, hematological and biochemical parameters, and carcass characteristics of Nile tilapia (Oreochromis niloticus) reared in a cage culture system. Four diets were tested: two controls (3.100 and 3.300 kcal/kg, without Cr-met) and two supplemented with Availa®Cr at the same energy levels. The experiment lasted 140 days. Isolated supplementation with Cr-met increased survival rate but did not affect zootechnical parameters. Energy levels, evaluated separately, also did not influence productive performance. However, in the interaction, the best zootechnical performance was observed in the Control 3.100 kcal/kg diet, while the Control 3.300 kcal/kg treatment showed reduced biomass gain. Regarding carcass composition, Cr-met supplementation reduced mineral matter and phosphorus contents.
Hepatic glycogen was higher in fish fed the Control 3.300 kcal/kg diet. Among enzymes, lower hepatic AST activity was observed in the Availa®Cr 3.300 treatment, and lower muscular ALT activity in the Control 3.100 group, while both enzymes showed higher activity in Availa®Cr 3.100. For hematological parameters, the isolated Control 3.300 kcal/kg diet promoted higher hemoglobin and MCHC values and lower MCV and MCH.
Cr-met supplementation increased MCV and MCH but reduced RBC. In the interaction, the highest MCV and MCH and the lowest RBC occurred in the Availa®Cr 3,100 treatment. In the biochemical profile, the isolated Control 3.300 diet increased total plasma protein, while Cr-met increased plasma protein and glucose. In the interaction, triglycerides were higher in the Control 3.100 and Availa®Cr 3.300 treatments. Therefore, the Availa®Cr 3.300 diet improved protein metabolism and increased amino acid availability for protein synthesis, without compromising growth performance. Based on these results, the use of Availa®Cr 3.300 is recommended in Nile tilápia diets to enhance productive performance, metabolic health, and survival rate in intensive systems.
