Plant essential oils against Aeromonas hydrophila: in vitro activity and their use in experimentally infected fish.

AIMS: The aims of this study were to investigate the in vitro antibacterial activity of the essential oils (EOs) of Hesperozygis ringens (HREO), popularly known as 'espanta-pulga' and two different species of basil, Ocimum gratissimum (OGEO) and Ocimum americanum (OAEO), as well as, the potential of these products to be used in silver catfish (Rhamdia quelen) infected with Aeromonas hydrophila. METHODS AND RESULTS: OGEO and HREO showed better antibacterial activity in vitro. Subinhibitory concentrations of all EOs inhibited haemolysis caused by Aer. hydrophila in fish erythrocytes (100% reduction for OAEO at 100 µg ml(-1) and more than 90% for HREO and OGEO at 150 µg ml(-1) ). However, OAEO and HREO showed the best survival results (75 and 70% respectively) after their use as treatment (therapeutic baths-1 h daily/5 days) in silver catfish experimentally infected with Aer. hydrophila. A second in vivo assay using healthy fish was conducted to verify the potential of the EOs (preventive baths-1 h daily/5 days) to promote fish survival. Fish exposed to HREO and OAEO and their diluent (ethanol) showed significant lower haematocrit values and higher complement system activity compared to control. Plasma cortisol level was significantly higher in the groups exposed to both EOs. There was no significant difference in survival of silver catfish challenged with Aer. hydrophila after preventive baths with HREO, OAEO and control group. CONCLUSIONS: All tested EOs showed in vitro antibacterial properties against Aer. hydrophila and HREO and OAEO showed potential to be used in the treatment of infected fish. SIGNIFICANCE AND IMPACT OF THE STUDY: These products can be used in aquaculture as therapeutic and prophylactic agents against fish pathogens, with antimicrobial and/or immunostimulant properties.

Farelo de tungue in natura ou detoxificado na alimentação de carpa húngara (Cyprinus carpio) / In natura or detoxified tung meal in feeding Hungarian carp (Cyprinus carpio)

Este estudo avaliou a substituição parcial de farinhas de origem animal pelo farelo de tungue como fonte proteica no arraçoamento de carpa húngara. Os tratamentos compreenderam a inclusão de farelo de tungue in natura ou detoxificado (obtido após aplicação de tratamento químico ao farelo), e o tratamento referência consistiu de base proteica composta por farinha de carne e ossos suína e farinha de peixe. O período de alimentação foi de 63 dias. No decorrer de 30 dias experimentais não foi observada diferença em indicadores de crescimento entre os animais que consumiram as rações controle e com farelo de tungue tratado quimicamente, porém o consumo da ração com farelo de tungue in natura provocou redução no desempenho até o final do período experimental. Após 63 dias de arraçoamento, alguns indicadores de crescimento mostraram-se inferiores também para o tratamento que continha farelo de tungue tratado em relação ao controle. A análise bioquímica no plasma e no fígado revelou aumento de triglicerídeos, glicogênio, glicose e a utilização de outras fontes, possivelmente aminoácidos, como precursores energéticos na produção de energia quando os animais consumiram a dieta com farelo de tungue in natura em relação às demais, o que refletiu na menor concentração de proteína e na maior deposição de gordura na carcaça. Em relação à atividade de enzimas digestivas, tripsina apresentou atividade aumentada no tratamento com farelo de tungue in natura e protease ácida, quimotripsina, amilase e lipase não foram alteradas em nenhum dos tratamentos avaliados...

This study evaluated the partial replacement of animal meal by tung meal as protein source in feeding Hungarian carp. The treatments consisted of the inclusion of in natura or detoxified tung meal (obtained after chemical treatment applied to tung meal) as well as the reference treatment in which the protein basis was composed of meat and bone pork meal and fish meal. The feeding period was 63 days. During 30 experimental days no difference was observed in growth indicators among animals fed the control diet or with chemically treated tung meal, however, the consumption of diets with in natura tung meal caused reduced performance until the end of the experimental period. After 63 days of feeding, some growth indicators were also are lower for the treatment containing treated tung meal compared to control. Biochemical analysis in plasma and liver revealed increased triglycerides, glycogen, glucose and use of other sources, possibly amino acids, as precursors in the production of energy when animals consumed the diet with in nature tung meal in relation to others, which reflected in lower levels of protein and higher fat deposition in the carcass. Regarding the activity of digestive enzymes, trypsin showed increased activity in the treatment with in natura tung meal and acid protease, chymotrypsin, amylase and lipase were not changed in any of the treatments...