Dietary administration of Bacillus subtilis on hematology and non-specific immunity of Nile tilapia Oreochromis niloticus raised at different stocking densities.

An 84-day feeding trial was conducted to evaluate the effect of the dietary administration of Bacillus subtilis on the growth performance, body composition, intestinal probiotic recovery, hematology, and non-specific immunity of Nile tilapia (Oreochromis niloticus) raised at two stocking densities. Five hundred twenty male Nile tilapias (32.63 ± 1.25 g) were distributed in 16,800-L tanks. The experimental design was completely randomized using four replications and a 2 × 2 factorial scheme with two stocking densities (18.75 fish m(-3) 62.50 fish m(-3)) and two diets (control and with probiotic). The probiotic-supplemented diet included 5 × 10(6) CFU g feed(-1). There were no significant differences (P > 0.05) in the growth performance, body composition, and levels of cortisol and glucose between the animals fed with the control diet and the animals fed with the probiotic-supplemented diet. Differences in the growth performance were observed between the fish reared at different stocking densities; in particular, the fish raised at the high stocking density exhibited reduced weight gain, feed intake, and specific growth rate compared with those raised at the low stocking density. The B. subtilis remained viable after its inclusion in the feed, storage, and passage through the stomach, which demonstrations the feasibility of using this bacteria as a probiotic. Higher values (P < 0.05) in the plasma lysozyme levels and phagocytic activity were observed in the fish that received the probiotic-supplemented diet and reared at the high stocking density, but this difference was not observed in the fish raised at the low stocking density and fed the different diets. The administration of the probiotic caused decreases in the number of erythrocytes and the hematocrit level in the fish reared at the high stocking density, but these erythrocytes showed higher values of mean corpuscular hemoglobin. The stocking density was shown to be a stressor agent that causes a lower fish growth rate. The fish fed the control diet and raised at the high stocking density had lower lysozyme levels than the fish subjected to the other treatments. The inclusion of the probiotic bacteria B. subtilis at a concentration of 5 × 10(6) CFU g feed(-1) benefited the innate immune system of Nile tilapia by decreasing the stress associated with exposure to a high stocking density, increasing the mean corpuscular hemoglobin, and improving the innate immune system (lysozyme and phagocytic activities of macrophages).

Tempo de migração dos macrófagos em matrinxã, Brycon amazonicus, por meio da técnica de inoculação de leveduras Saccharomyces cerevisiae / Macrophagic migration time in matrinxã, Brycon amazonicus, through inoculation of yeast, Saccharomyces cerevisiae, technique

Na aquicultura são utilizados análises da ativação e incremento da migração de macrófagos, com intuito de verificar a capacidade imunológica inespecífica dos peixes frente a um desafio. Neste sentido, o objetivo deste estudo foi determinar o tempo de migração de monócitos/macrófagos para a cavidade peritoneal em matrinxã, Brycon amazonicus, por meio da técnica de inoculação de leveduras Saccharomyces cerevisiae, e verificar as possíveis alterações dos parâmetros hematológicos após o estímulo. Foram utilizados 30 matrinxãs com peso médio de 101,55 ± 24,50 g e comprimento médio de 19,75 ± 1,72 cm. Os tempos de inoculação utilizados foram 2, 4, 8 e 12 horas, sendo utilizados 6 animais por tempo. Após os períodos de incubação (2, 4, 8 e 12 horas), os exemplares foram anestesiados e alíquotas de sangue foram coletadas por punção do vaso caudal, para a análise: número total de células, contagem diferencial e total dos leucócitos e contagem total de trombócitos, hematócrito, taxa de hemoglobina e índices hematimétricos (VCM, HCM e CHCM). Os resultados mostram que a capacidade fagocítica do macrófago não apresentou diferenças significativas entre os tempos experimentais. Com relação ao índice fagocítico, o tempo de 2 horas representa o tempo em que os macrófagos fagocitaram maior número de leveduras com diferenças significativas em relação aos outros tempos experimentais, indicando que este tempo (2 horas) de incubação foi suficiente para a migração e ativação máxima dos macrófagos da cavidade peritoneal, da espécie estudada. Os valores do número de eritrócitos apresentaram diferenças entre os tempos de incubação. Entretanto, os valores dos outros parâmetros hematológicos não apresentaram diferenças significativas.

In aquaculture, analysis of activation and increased macrophages migration are used in order to verify the ability of the nonspecific immune fish exposed to a challenge. This study aimed to determine the time of macrophages migration in matrinxã, Brycon amazonicus, through the technique of yeast Saccharomyces cerevisiae inoculation, verifying possible changes in hematological parameters. Thirty animals with average weight of 101.55 ± 24.50 g and average length of 19.75 ± 1.72 cm were employed. The experimental inoculation periods were 2, 4, 8 and 12 hours. Thereafter, animals were anesthetized and blood was withdrawn through a caudal puncture for the determination of total erythrocytes number, differential and total leukocyte counts and total thrombocytes count, hematocrit, hemoglobin concentration and calculation of the erythrocytes index. The results for the phagocytic capacity were not significantly different between experimental periods. In the phagocytic index, the period of 2 hours presented the highest rate of phagocytized cells, indicating that 2 hours of incubation was sufficient for the macrophages migration in B. amazonicus. The number of erythrocyte was the only parameter that presented significant difference among periods.