Suplementação de minerais quelatados a aminoácidos em dietas com baixa proteína para Tilápia do Nilo: cromo e zinco

Abstract

This study aimed to evaluate the effects of dietary supplementation with Cr-methionine (chelated chromium with methionine) and ZnAA (zinc-amino acid complex) in extruded diets containing reduced protein levels in relation to productive performance, carcass composition, nutrient retention, and hematological, biochemical, and metabolic responses in juvenile Nile tilapia. For the evaluation of Cr-methionine, the animals were fed two control diets (without the addition of Cr-methionine), which were divided into a positive control (311 g kg-1 crude protein) and a negative control (255 g kg-1 crude protein). Five other experimental diets (255 g kg-1 crude protein) with supplementation of 0.2, 0.4, 0.6, 0.8, and 1.0 mg Cr-methionine kg diet−1 were conducted. For the evaluation of ZnAA, the animals were fed two control diets (without the addition of ZnAA), categorized as a positive control (295 g kg-1 crude protein) and a negative control (264 g kg-1 crude protein). Five other experimental diets (264 g kg-1 crude protein) with supplementation of 0.0, 20, 40, 60, 80, and 100 mg kg−1 were tested. The duration of the experiments was 9 weeks. Fish from the 0.8 and 1.0 mg Cr-methionine kg diet−1 treatments showed zootechnical variables similar to the positive control. Gross energy values and energy retention were significantly higher in the 0.6 mg Cr-methionine kg diet−1 treatment than in the positive control. The negative control and 80 mg ZnAA kg diet−1 treatments showed similar growth performance to the positive control. Lipid values and carcass nitrogen retention were significantly lower in the positive control than in the other treatments. In conclusion, it is possible to recommend supplementation with Cr-methionine and ZnAA in low-protein diets for Nile tilapia to promote improvements in growth performance and reduce dietary protein through better nutrient utilization without affecting metabolism.