Efeito da adição da levedura yarrowia lipolytica na dieta de tilápia do nilo oreochromis niloticus sobre os parâmetros hematológicos e imunes

Abstract

The fish production currently performed in high density can lead to stressful situations, leading to physiological changes such as reduced growth and greater susceptibility to parasites. The use of yeasts as additives in fish feed has the potential to be a source of nutrients as well as acting as immunostimulants because infections. The use of agroindustrial residues such as cassava peel converted by microorganisms and used as an additive in animal feed is an ecologically friendly destination for these residues. The present work evaluated the effects of adding fermented biomass of the yeast Yarrowia lipolytica on zootechnical parameters (weight gain, length gain and survival rate), hematological (erythrocytes, hematocrit, hemoglobin, MCV, MCHC, MHC), immune (lysozyme and myeloperoxidase levels and concentration of nitrite / nitrate) in the plasma and kidney of Nile tilapia (Oreochromis niloticus). 320 juveniles of tilapia were used, divided into 4 experimental groups with different levels of biomass addition of Y. lipolytica: control (without addition), T1 (3%), T2 (5%) and T3 (7%) with four replicates for each group. After 35 days of feeding, 24 animals from each experimental group were collected and sacrificed for the analysis. The use of Y. lipolytica biomass added to the feed promoted significant differences in the evaluated zootechnical and hematological parameters. The addition promoted an improvement in the innate immune response capacity because there was an increase in defense cells such as neutrophils and monocytes in the animals' blood; it also led to an increase in levels of lysozyme, myeloperoxidase and plasma nitrite / nitrate content correlated with increases in leukocyte levels in the bloodstream. In the kidney it promoted an increase in the levels of myeloperoxidase, but did not alter the levels of lysozyme and the nitrite / nitrate content indicating that the main immunostimulatory action targets of the yeast are in the bloodstream. Considering the physiological responses of the hematological and immune systems after supplementation, we can conclude that the use of yeast in lower concentrations, such as 3 and 5%, is effective and safe for application as immunostimulants in the Nile tilapia diet. Also, the 7% supplementation showed the best results to zootechnical parameters.