BACKGROUND: Microencapsulation of probiotic bacteria is an area that has rapidly expanded over the recent years. It is one of the new methods of improving probiotics stability, through which the biological agents are protected with an enclosed coating to release the active agents within the coating at a controlled rate in time and under special conditions.OBJECTIVES: The present study the aims to evaluate the effect of Lactobacillus plantarum microencapsulation with chitosan/alginate microparticles on the oxidative response of Nile tilapia fish (Oreochromis niloticus).METHODS: Herein, 240 pieces of Nile tilapia, with an average weight of 15.56±0.02 g, were randomly divided into four groups as follows: group1 or control with a diet without probiotics, groups 2, 3, and 4 respectively with a diet containing 108 Log CFU/g of unencapsulated Lactobacillus plantarum, a diet containing microencapsulated Lactobacillus plantarum, and with feed containing alginate with chitosan without the presence of bacteria. They were fed for 60 days at the rate of 2 % of body weight twice a day.RESULTS: The activity level of oxidative enzymes, biochemical factors, and liver enzymes of the Nile tilapia fish were investigated. The findings revealed that oxidative enzymes, biochemical factors, and liver enzymes were positively affected in the groups with microencapsulated Lactobacillus plantarum (P<0.05). The three enzymes of alanine transaminase, aspartate transaminase, and alkaline phosphatase were higher in the micro-encapsulated probiotic group compared to the two groups of probiotics and alginate with chitosan without the presence of bacteria, and all the three groups performed better compared to the control (P<0.05).CONCLUSIONS: Microencapsulation of probiotics maximizes the efficiency of probiotics in reducing oxidative stress.

Female Oreochromis niloticus were exposed to 1/10 LC50 (0.21ppm) of butachlor herbicide for 6 weeks. Weekly specimens were taken for fecundity estimation. Also hormonal and enzymatic levels were determined in addition histopathological alterations in ovaries and liver were detected. Butachlor exerted drastic effects on absolute and relative fecundity. Sex hormones (testosterone "T" and estradiol "E2") dropped significantly. The high significantly decline in Total Ripen Egg Number was assisted by the coagulative necrosis and oocytic atrasia in ovaries. In addition, thrombus formation and hepatoadenocarcinoma were pronounced in the liver and resulted in the significant drop in ALT and total protein levels. So, it is recommended to apply the biological control of pests in substitution to herbicids in rice fields.

Killing activity of fresh Oreochromis niloticus serum was used as an indicator of the natural immunity. Serum killing activity was tested in temperature stressed fish exposed to 32 ±1°C to different Pseudomonas fluorescens strains. As a clinical estimate of natural immunity and disease resistance, experimental challenge with P. fluorescens strains was conducted. The results cleared that serum killing activity at 32±1°C was almost stopped where fish got infected after bacterial challenge. On the other hand, control fish group kept at 23± 1°C developed serum killing activity and resistance to the acquisition of infection after challenge. A correlation was found between resistance activities of P. fluorescens strains to serum killing and their corresponding courses of infection after bacterial challenge. However, the results of experimental challenge conducted at 32±1°C suggested that the immunocompromising state resulted from the stress of inability to withstand high water temperature is exclusively the critical aspect for the induction of infection.

The present study evaluated the dietary supplementation with essential oil of Lippia alba on the hemato-immunological parameters of Nile tilapia (Oreochromis niloticus) submitted to acute inflammation induced by carrageenin injection in the swim bladder. For a period of 45 days, 96 fish were divided in four treatments in triplicate, as follows: fish fed supplemented diet with essential oil of L. alba (4 mL kg-1 dry ration) injected with carrageenin; fish fed supplemented diet with cereal alcohol injected with carrageenin; fish fed unsupplemented diet with essential oil injected with carrageenin; fish fed unsupplemented diet and noninjected. Cortisol levels, erythrogram, leukogram and the inflammatory infiltrate were analyzed 6 h after inflammatory stimulus. Carrageenin-injected fish showed acute inflammatory reaction in the swim bladder characterized by higher infiltrate of neutrophils and monocytes. The circulating neutrophils number was significantly higher in fish fed L. alba when compared to other treatments. No difference in cortisol levels was found. For dose, time and administration form tested, supplementation with essential oil of L. alba did not present anti-inflammatory activity. On the other hand, influence of dietary supplementation was observed on the neutrophils number after induced aerocystitis highlighting its immunomodulatory characteristic.

Environmental changes affect fish homeostasis, turning them more susceptible to diseases. In Brazil, outbreaks of Streptococcus agalactiae infection have been reported in Nile tilapia when they are outside of their thermal comfort zone. This investigation evaluated mortality rate and which were the most infected organs at temperatures that naturally occurred in southern of Brazil. Forty Nile tilapia (Oreochromis niloticus) were infected with S. agalactiae and distributed in four groups (n=10) and each group was exposed to a different temperature: G1: 24°C, G2: 26°C, G3: 28°C, and G4: 32°C. Fish were monitored for 10 days. In this period, fish that presented irreversible clinical signs were sacrificed and samples of brain, liver, and kidney were collected for bacteriological and molecular analysis. Signs compatible with a streptococcal infection were observed in all groups. Highest mortality rates occurred at 24°C and 32°C. The brain was the most affected organ with the highest percentage of isolation of S. agalactiae by both methods of diagnosis. The results suggest that, as in mammals, temperatures that are further away from the comfort zone influence fish homeostasis, increasing susceptibility to bacterial infections.

O objetivo deste trabalho foi avaliar os efeitos de três diferentes granulometrias de rações fareladas (0,25, 0,35 e 0,50 mm) sobre o ganho de peso, crescimento, sobrevivência e proporção sexual para larvas de tilápia-do-Nilo (Oreochromis niloticus) aos 30, 60 e 90 dias de idade. Nos primeiros 30 dias de vida, as larvas foram revertidas com rações contendo hormônio 17 α-metiltestosterona na dosagem de 60 mg/kg de ração, respeitando-se as diferentes granulometrias e após este período, foram medidas, pesadas e contadas para cálculo da taxa de sobrevivência. Para as variáveis biométricas de peso e comprimento total, foi utilizado o delineamento inteiramente casualizado (DIC), em parcelas subdivididas, com três tratamentos e três repetições, considerando-se parcelas as três granulometrias de ração e subparcelas as três idades. Ao término do estudo, os peixes alimentados com as granulometrias 0,35 e 0,25 mm, obtiveram os melhores resultados para o ganho de peso (14,42 g e 13,36 g) e comprimento total (83,13 mm e 82,72 mm), não diferindo estatisticamente e as rações com diâmetros de grão 0,50 e 0,35 mm resultaram em 96,66% e 93,33% de machos, respectivamente, após análise histológica das gônadas, sem diferenças estatísticas entre os tratamentos. | The aim of this work was to evaluate the effects of three different diameters of crumble diets (0.25, 0.35 and 0.50 mm) on weight gain, growing, survival and sexual proportion to Nile tilapia (Oreochromis niloticus) larvae with 30, 60 and 90 days of age. In the first 30 days of age larvae were submitted to sex reversion with diets containing the hormone 17 &#945;-methyltestosterone in a dosage of 60mg/kg of ration, respecting the different diameters and after this period, larvae were measured, weighed and counted for calculation of survival taxes. For the biometrical parameters as weight and total length a completely randomized design was used in subdivided installments with three treatments and three repetitions, considering installments the three diameters of diet and the sub installments, the three ages. In the end of this study, fish fed with diets of grain diameters 0.35 and 0.25 mm obtained the best results for weight gain (14.42 g and 13.36 g) and total length (83.13 mm and 82.72 mm), although these results were not statistically significant, and diets with grain diameters 0.50 and 0.35 mm resulted in 96,66 % and 93,33% of males, respectively, after histological analysis of gonads, without statistics differences between the treatments.

O objetivo deste trabalho foi avaliar os efeitos de três diferentes granulometrias de rações fareladas (0,25, 0,35 e 0,50 mm) sobre o ganho de peso, crescimento, sobrevivência e proporção sexual para larvas de tilápia-do-Nilo (Oreochromis niloticus) aos 30, 60 e 90 dias de idade. Nos primeiros 30 dias de vida, as larvas foram revertidas com rações contendo hormônio 17 α-metiltestosterona na dosagem de 60 mg/kg de ração, respeitando-se as diferentes granulometrias e após este período, foram medidas, pesadas e contadas para cálculo da taxa de sobrevivência. Para as variáveis biométricas de peso e comprimento total, foi utilizado o delineamento inteiramente casualizado (DIC), em parcelas subdivididas, com três tratamentos e três repetições, considerando-se parcelas as três granulometrias de ração e subparcelas as três idades. Ao término do estudo, os peixes alimentados com as granulometrias 0,35 e 0,25 mm, obtiveram os melhores resultados para o ganho de peso (14,42 g e 13,36 g) e comprimento total (83,13 mm e 82,72 mm), não diferindo estatisticamente e as rações com diâmetros de grão 0,50 e 0,35 mm resultaram em 96,66% e 93,33% de machos, respectivamente, após análise histológica das gônadas, sem diferenças estatísticas entre os tratamentos.