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Efeito de dietas experimentais na sobrevivĂȘncia de robalo-europeu (Dicentrarchus labrax) infetado com Tenacibaculum maritimum
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A aquacultura Ă© um setor em expansĂŁo que enfrenta desafios relacionados com doenças bacterianas, como a tenacibaculose marinha, causada por Tenacibaculum maritimum. A aplicação de dietas com potencial imunomodulador constitui uma abordagem promissora, ao permitir otimizar simultaneamente o crescimento e a resistĂȘncia dos peixes. O presente estudo tem como objetivo avaliar o desempenho do robalo-europeu (Dicentrarchus labrax) submetido a dietas experimentais, formuladas por uma empresa comercial, de modo a determinar se estas influenciam o crescimento e potenciam a resposta imunitĂĄria dos peixes quando desafiados com Tenacibaculum maritimum por imersĂŁo. Para tal, juvenis de robalo-europeu foram alimentados durante 34 dias com 4 dietas distintas e, posteriormente, submetidos a um ensaio de infeção por
imersĂŁo (5,5 Ă 10ⶠUFC/mL, durante 2 horas) com a estirpe A155, isolada de linguado senegalĂȘs (Solea senegalensis). Foram avaliados os parĂąmetros de crescimento, os nĂveis de anticorpos (determinados por ELISA) e a presença de DNA bacteriano nos tecidos da pele e das brĂąnquias (detetado por PCR). O tratamento B (dieta 1) destacou-se pelo melhor desempenho produtivo (taxa de crescimento especĂfico (SGR) mais elevado e, Ăndice de conversĂŁo alimentar (FCR) mais baixo), enquanto o tratamento D (dieta 3) apresentou a menor eficiĂȘncia alimentar. No entanto, estas diferenças nĂŁo se refletiram na imunidade, uma vez que os testes ELISA nĂŁo revelaram nĂveis relevantes de anticorpos em nenhum tratamento. No desafio bacteriano, registou-se sobrevivĂȘncia total e ausĂȘncia de sinais clĂnicos, sendo o DNA bacteriano apenas detetado nas primeiras 24 h
apĂłs a infeção, desaparecendo Ă s 48 horas, o que sugere que a colonização inicial foi rapidamente controlada. Deste modo, embora as dietas experimentais tenham influenciado o crescimento, nĂŁo conferiram proteção adicional contra T. maritimum. A ausĂȘncia de doença poderĂĄ estar associada Ă baixa virulĂȘncia da estirpe utilizada, Ă s condiçÔes ambientais favorĂĄveis e ao desenho experimental adotado, realçando a necessidade de futuros ensaios com modelos de infeção otimizados e caracterização detalhada da composição dietĂ©tica.
Aquaculture is a rapidly expanding sector that faces significant challenges related to bacterial diseases, such as marine tenacibaculosis, caused by Tenacibaculum maritimum. The use of diets with immunomodulatory potential represents a promising approach, as it allows the simultaneous optimization of fish growth and resistance to infections. The present study aimed to evaluate the performance of European sea bass (Dicentrarchus labrax) fed experimental diets formulated by a commercial company, to determine whether these diets influence growth and modulate the immune response when fish are challenged with T. maritimum via immersion. For this purpose, seabass juveniles were fed for 34 days with four different diets and subsequently subjected to an immersion infection trial (5.5 Ă 10ⶠCFU/mL, for 2 hours) with the A155 strain, isolated from Solea senegalensis. Growth parameters, antibody levels (determined by ELISA), and the presence of bacterial DNA in skin and gill tissues (detected by PCR) were assessed. Treatment B (diet 1) stood out for its best productive performance (higher specific growth rate (SGR) and lower feed conversion ratio (FCR)), whereas treatment D (diet 3) showed the lowest feed efficiency. However, these differences were not reflected in immunity, as ELISA tests did not reveal relevant anÆbody levels in any treatment. In the bacterial challenge, total survival and absence of clinical signs were recorded, with bacterial DNA being detected only within the first 24 h atier infection and disappearing by 48 h, suggesting that the initial colonization was rapidly controlled. Thus, although the experimental diets influenced growth, they did not confer additional protecÆon against T. maritimum. The absence of disease may be associated with the low virulence of the strain used, favorable environmental condiÆons, and the experimental design, highlighting the need for future trials with optimized infection models and a detailed characterization of diet composition.
Aquaculture is a rapidly expanding sector that faces significant challenges related to bacterial diseases, such as marine tenacibaculosis, caused by Tenacibaculum maritimum. The use of diets with immunomodulatory potential represents a promising approach, as it allows the simultaneous optimization of fish growth and resistance to infections. The present study aimed to evaluate the performance of European sea bass (Dicentrarchus labrax) fed experimental diets formulated by a commercial company, to determine whether these diets influence growth and modulate the immune response when fish are challenged with T. maritimum via immersion. For this purpose, seabass juveniles were fed for 34 days with four different diets and subsequently subjected to an immersion infection trial (5.5 Ă 10ⶠCFU/mL, for 2 hours) with the A155 strain, isolated from Solea senegalensis. Growth parameters, antibody levels (determined by ELISA), and the presence of bacterial DNA in skin and gill tissues (detected by PCR) were assessed. Treatment B (diet 1) stood out for its best productive performance (higher specific growth rate (SGR) and lower feed conversion ratio (FCR)), whereas treatment D (diet 3) showed the lowest feed efficiency. However, these differences were not reflected in immunity, as ELISA tests did not reveal relevant anÆbody levels in any treatment. In the bacterial challenge, total survival and absence of clinical signs were recorded, with bacterial DNA being detected only within the first 24 h atier infection and disappearing by 48 h, suggesting that the initial colonization was rapidly controlled. Thus, although the experimental diets influenced growth, they did not confer additional protecÆon against T. maritimum. The absence of disease may be associated with the low virulence of the strain used, favorable environmental condiÆons, and the experimental design, highlighting the need for future trials with optimized infection models and a detailed characterization of diet composition.
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Palavras-chave
Aquacultura Tenacibaculose marinha Dicentrarchus labrax Dietas experimentais Imunonutrição