Blood transports lysine and other nutrients derived from the diet and ensures good health and greater productivity for the fish. Therefore, this study aimed to verify the hematological behavior of juvenile tambaqui Colossoma macropomum nourished with levels of 9.72, 12.84, 15.96, 19.08 and 22.20 g.Kg-1 of total lysine, corresponding, respectively, to the supplementation levels with L-lysine: 0.00, 4.00, 8.00, 12.00, 16.00 and 20.00 g.Kg-1 of L-lysine. The blood of the fish was collected in the initial and final periods by puncture of the caudal vein. The variables were validated by ANOVA and Tukey's test (p< 0.05). No differences were found for hemoglobin, hematocrit, CHCM, leukocytes of the eosinophil and monocyte types, and thrombocytes (p> 0.05). The changes observed in total leukocytes were not attributed to diets (p= 0.00). Means of CMV, HCM, lymphocytes and neutrophils, varied over the initial period, but not in regard to different lysine levels (p< 0.05). Thus, it is concluded that the varying lysine levels of the diets did not compromise the hematological parameters analyzed.
This study aimed to determine the dietary lysine requirements of juvenile Colossoma macropomum tambaqui based on growth performance. We also evaluated gut and hepatic histomorphometry as well as blood metabolites in accordance with the increased levels of dietary lysine. The juveniles (33.88 ± 2.47 g) were fed until apparent satiation with diets containing 6.60, 9.72, 12.84, 15.96, 19.08 and 22.20 g/kg of lysine. Fish were randomly distributed in groups of 10 fish per tank and assays were performed in triplicate, during 90 days. Tambaqui fed with 15.96 g/kg dietary lysine showed higher final weight (p = 0.001) and optimized feed conversion ratio (p = 0.001). Morphohistological modifications were present in livers of fish fed with low levels of lysine. In the proximal intestine, mucosa layer density was greater at the level of 15.96 g/kg (p = 0.001). In the middle intestine, height (p = 0.001) and perimeter (p = 0.001) of the villi were greater at low levels of lysine (respectively, 9.72 and 12.84 g/kg dietary lysine). Tambaqui fed with 15.96 g/kg of lysine achieved higher plasma protein concentrations (p = 0.01). Using the second-order polynomial regression analysis as support, and based on protein efficiency rate and body weight gain, dietary lysine requirement for juvenile tambaqui was calculated as 15.4–15.6 g/kg of diet (5.7–5.8% of dietary protein).
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