DIFFERENTIAL LEUKOCYTE COUNTS OF NILE TILAPIA FED DIETS SUPPLEMENTED

Abstract

This research was realized in two periods, one pre experimental in 112 days and other experimental in 43 days, aiming to evaluate the effects of vitamin C and lipid on differential leukocyte counts of fish submitted to temperature stress. Leukocyte cells were evaluated at the beginning and the end of the experiment. The experiment used a 2 x 3 factorial design with vitamin C (300.0; 600.0 and 1,200.0 mg/kg diet) and lipid levels (8.0 and 12.0%) with four replicates, plus absence of nutrient test and 6.0% lipids and 125.0 mg/kg vitamin C diet. Diets were formulated to contain 32.0% of DP. Fish were stocked into 24 40-L aquaria at a density of two fish/aquarium, with weight of 105.13 ± 19.71 g. Water temperature was kept at 18.0°C during 25 days and at 15.0°C during 11. Low temperature determine a decrease on leucocytes and lymphocytes and an increase on neutrophils and monocytes. There was a significant interaction between phase x vitamin C and phase x lipid. It was concluded that vitamin C and lipid supplementation improve immune response; low temperature determine a decrease in fish resistance; levels of vitamin C supplementation above the requirement and 8.0 and 12.0% of lipid on diet determine a better resistance.

KEY WORDS: Ascorbic acid, low temperature, Oreochromis niloticus, resistance, white blood cell.