Efeito da inclusão de níveis baixos de fumonisinas na dieta de truta arco-íris (Onchorynchus mykiss)
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2015
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As micotoxinas são metabolitos secundários provenientes de fungos e são produzidas essencialmente por três géneros de fungos, Fusarium spp, Aspergillus spp e Penicillium spp. Estas substâncias aparecem quando são reunidas certas condições específicas em relação ao alimento e ao meio exterior, sendo que a exposição por parte dos animais a estas pode dar origem a doença (micotoxicose).
O trabalho que se apresenta foi centrado nas fumonisinas, que constituem um grupo de micotoxinas produzidas por fungos do género Fusarium, principalmente pelas espécies F. verticillioides e F. proliferatum. O objectivo principal foi avaliar, até que ponto, um nível bastante baixo destas miotoxinas (0,05 mg kg-1), mas possivelmente expectável em dietas com uma componente de ingredientes de origem vegetal, poderia ter efeitos no crescimento, na eficiência alimentar e na anatomopatologia de juvenis de truta arco-íris.
Para o efeito, foram utilizadas quatro dietas experimentais para juvenis de truta arco-íris, formuladas de modo a respeitar as suas exigências nutricionais. Foi utilizada uma dieta controlo (CTRL) que continha farinha e óleo de peixe como principais fontes de proteína e de gordura. Esta dieta serviu de base para a formulação das outras dietas experimentais: uma dieta (FUM) que diferiu na sua composição devido à inclusão de um nível bastante reduzido de fumonisina (0,05 mg kg-1); uma terceira dieta (MFIX) onde foi utilizado um composto que teria como função contrariar o efeito da micotoxina e uma quarta dieta (FUM+MFIX) com inclusão da micotoxina e do produto previamente referido. Foram utilizados doze grupos homogéneos de cinquenta peixes (peso médio inicial: 19±0,3g), distribuídos aleatoriamente por doze tanques de fibra de vidro, constituindo, assim, triplicados de cada tratamento. Os peixes foram alimentados com as dietas experimentais durante 58 dias.
No final do ensaio foram avaliados os parâmetros do crescimento e da eficiência alimentar, a composição corporal final dos peixes, bem como a sua análise anatomopatológica. Após a análise dos resultados, não foram observadas diferenças significativas (P>0,05) para o crescimento e eficiência do alimento. Todavia, foram detectadas diferenças significativas no que diz respeito ao índice hepatossomático e à análise anatomopatológica. Partindo do principio que este trabalho se trata de uma primeira abordagem a esta espécie, face aos resultados obtidos, estes sugerem que esta espécie, a esta idade e peso (19 gramas), se mostra sensível em termos hepáticos a concentrações baixas de fumonisinas.
Após consulta bibliográfica, cremos que este trabalho é a primeira abordagem do género realizada em truta arco-íris.
Mycotoxins are secondary metabolites originated from fungi, being produced essentially by three genera of fungi, Fusarium spp, Aspergillus spp and Penicillium spp. These substances appear when specific conditions are fulfilled regarding the food and the environment and, in consequence, the exposure of these to animals may lead to disease (mycotoxicosis). The work presented here focused on fumonisins, which are a group of mycotoxins produced by fungi of the Fusarium genera, mainly by the species F. verticillioides and F. proliferatum. The main objective was to evaluate, to what extent, a rather low level of these myotoxins (0.05 mg kg-1), although expected in diets with a component of plant ingredients, could have effects on growth, feed efficiency and anatomopathology of juvenile rainbow trout. To this end, there were used four experimental diets for rainbow trout juveniles. These were formulated to meet their nutritional requirements. A diet control (CTRL) containing fish meal and fish oil as the main source of protein and fat was used. This diet was the basis for the formulation of the other experimental diets: a diet (FUM) that differed in composition due to the inclusion of a very low level of fumonisin (0.05 mg kg-1); a third diet (MFIX) containing a compound counteracting the effect due to the presence of mycotoxin and a fourth diet (FUM + MFIX) with inclusion of the mycotoxin and the before mentioned compound. Twelve homogeneous groups of fifty fish were used (average weight: 19 ± 0.3g) and randomly distributed over twelve fibreglass tanks, thus constituting triplicates of each treatment. The fish were fed with the experimental diets for 58 days. Finally, we evaluated the growth parameters and feed efficiency, the final body composition of the fish and its anatomopathology analysis. According to the results analysis, no significant differences were observed (P>0.05) for growth and feed efficiency. However, significant differences were found regarding the hepatosomatic index and the histopathological analysis. Assuming that this work represents a first approach to this specie, and given the results obtained, it suggests that this specie and for its age and weight (19 grams), the liver seems to be sensitive to low concentrations of fumonisin. After bibliographic research, it seems that this work is the first of its kind held in rainbow trout.
Mycotoxins are secondary metabolites originated from fungi, being produced essentially by three genera of fungi, Fusarium spp, Aspergillus spp and Penicillium spp. These substances appear when specific conditions are fulfilled regarding the food and the environment and, in consequence, the exposure of these to animals may lead to disease (mycotoxicosis). The work presented here focused on fumonisins, which are a group of mycotoxins produced by fungi of the Fusarium genera, mainly by the species F. verticillioides and F. proliferatum. The main objective was to evaluate, to what extent, a rather low level of these myotoxins (0.05 mg kg-1), although expected in diets with a component of plant ingredients, could have effects on growth, feed efficiency and anatomopathology of juvenile rainbow trout. To this end, there were used four experimental diets for rainbow trout juveniles. These were formulated to meet their nutritional requirements. A diet control (CTRL) containing fish meal and fish oil as the main source of protein and fat was used. This diet was the basis for the formulation of the other experimental diets: a diet (FUM) that differed in composition due to the inclusion of a very low level of fumonisin (0.05 mg kg-1); a third diet (MFIX) containing a compound counteracting the effect due to the presence of mycotoxin and a fourth diet (FUM + MFIX) with inclusion of the mycotoxin and the before mentioned compound. Twelve homogeneous groups of fifty fish were used (average weight: 19 ± 0.3g) and randomly distributed over twelve fibreglass tanks, thus constituting triplicates of each treatment. The fish were fed with the experimental diets for 58 days. Finally, we evaluated the growth parameters and feed efficiency, the final body composition of the fish and its anatomopathology analysis. According to the results analysis, no significant differences were observed (P>0.05) for growth and feed efficiency. However, significant differences were found regarding the hepatosomatic index and the histopathological analysis. Assuming that this work represents a first approach to this specie, and given the results obtained, it suggests that this specie and for its age and weight (19 grams), the liver seems to be sensitive to low concentrations of fumonisin. After bibliographic research, it seems that this work is the first of its kind held in rainbow trout.
Descrição
Dissertação de Mestrado Integrado em Medicina Veterinária
Palavras-chave
Oncorhynchus mykiss (truta arco-íris) , Dieta , Micotoxinas , Fumonisinas , Micotoxicose , Índice hepatossomático , Análise anatomopatológica