Abstract
This work will study the effects of the addition of mannanoligosaccharide in the Nile tilapia diet in four levels, during 45 days, in the productive performance, number of leukocytes and total thrombocytes, differential leukocyte counts, hematocrit tax, total protein, lisozyma, burst of the leukocytes, intestine morphology and survival after the challenge with the Streptococcus agalactiae bacteria. Will be used 450 juveniles of Nile tilapia weighting about 30 and 50 g distributed aleatory in 30 tanks with the capacity of 310 liters (5 treatments, 3 repetition, 15 fishes/tank), that will be supplied with water from an artesian well with continuous aeration. During the experimental period the fishes will be feed with five experimental rations, with 0.4, 0.8, 1.0 and 1.5%, and one ration without the mannanoligosaccharide (0). The diets will be served twice a day until the fishes are feedstuff. After the feed period (time 0, 30 and 45 days after the feeding), the fishes will be captured and the blood will be withdrawn for the evaluation of physiological parameters (glucose, total protein, count of blood cells, hematocrit and hemoglobin), immunological (lisozyma and burst of leukocytes), histological (intestine morphology) and the productive performance (growth and weight gain). After 45 days the fishes will be submitted to a challenge with Streptococcus agalactiae. The fishes will continue to be feed daily with the experimental diets for two weeks more taking note daily the clinical signs of bacterial and mortalities taxes.
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