Yeast and zinc as pro-nutrients in Nile tilapia (Oreochromis niloticus) diets: Hematological aspects

Abstract

This research evaluated the effect of supplementation of spray dried sugar-cane yeast and zinc (zinc oxide), as pro-nutrients in Nile tilapia diets, on some hematological parameters. Two hundred tilapia fingerlings with initial average weight (1.12±0.05 g) were distributed in 40 aquaria (5 fish/aquarium), in recirculating water system with controlled temperature. The experimental design was factorial 3x3 design (levels of yeast and zinc) plus an additional treatment (control), totaling 10 treatments with four replicates in completely randomized blocks. The experimental diets, isoproteic (30.0% DP) and isoenergetic (3,200 kcal ED/kg diet) were supplemented with three yeast levels (0.5, 1.0 and 2.0%) and three zinc levels (150, 300 and 600 mg/kg diet). An additional diet with no pro-nutrient was used (control). The number of erythrocytes, hematocrit, mean corpuscular volume, total plasmatic protein and macroscopic alterations on digestive tract were analyzed. After 90 days, results of hematocrit and mean corpuscular volume showed interaction between levels of yeast and zinc. It was concluded that the proposed levels of yeast and zinc did not provide severe alterations on the evaluated hematological parameters and that it is possible to use them in combination as pro-nutrients in Nile tilapia diets.