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ABSTRACT. The objective of this study was to assess the growth performance and the histomorphometric characterization of the middle intestine of GIFT strain Nile tilapia, Oreochromis niloticus juveniles fed probiotics, added either before or after the feed processing. The experimental design was completely randomized, with five treatments and five replications: pelleted feed without any probiotic; pelleted feed with inclusion of probiotic before the processing; pelleted feed with inclusion of probiotic after the processing; extruded feed without any probiotic and extruded feed with inclusion of probiotic after the processing. Two hundred and fifty juveniles were distributed in 25 aquaria (20L) and fed for 63 days. Differences in the mean values of total weight were found at the end of the experiment. After 42 days of feed intake, significant differences in feed conversion were verified for treatments with extruded diets when compared to the pelleted ones. The fishes fed diets supplemented with probiotic presented increase in the thickness of the epithelium of the intestine. The best zootechnical performance was observed in the extruded diet supplemented with probiotic added after the feed processing. of Bacillus toyoi in both the pelleted and the extruded diets promoted an increase in the thickness of the epithelial layer of the middle intestine.

A commercial probiotic containing Bacillus subtilis (109 CFU g-1) was evaluated in caged matrinxã, Brycon amazonicus, by measuring hematological parameters and macrophage activity after 42 and 84 days after feeding. The product was added to commercial feed using 2% soybean oil as a protectant. A randomized three-treatment experiment was performed using four replicates per treatment. The groups included: (a) control without probiotic, (b) 5 g kg-1 probiotic, and (c) 10 g kg-1 probiotic. For hematological analysis, eight fish per treatment were used to determine total cell count (RBC); thrombocytes, differential, and total leukocyte count (TLC); hematocrit (Htc); hemoglobin tax; mean corpuscular volume (MCV); and mean corpuscular hemoglobin concentration (MCHC). Furthermore, plasma cortisol and glucose levels were measured in blood samples. Macrophage phagocytic activity was evaluated by injecting Saccharomyces cerevisiae (11,000 cells in a 3 mL volume) into the coelomic cavity incubating for 8 hours. Addition of probiotics to the diet of caged matrinxã altered the Htc, RBC, MCV, MCHC, TLC, lymphocyte, and eosinophil values. We observed increased cortisol and glucose levels and phagocytic activity, but no increase in the phagocytic index. We thus conclude that supplementing caged Brycon amazonicus with probiotics improves their non-specific immunity and alters blood profiles.