Efeito do extrato de alho (Allium sativum) sobre o sistema hematol?gico, imune e meteb?lico de jundi?s Rhamdia quelen (Quoy & Gaimard, 1824)

Considering the commercial fish production, different species have been produced in an intensive way with high storage densities / m? of water. This type of cultivation promotes extremely stressful conditions to the animals causing disturbances in their physiological state. This condition can lead to reduced weight gain and growth, reproduction performance and low resistance to pathogens, being susceptible to attack by parasites, bacteria, viruses and / or fungi. Taking these into account, there is a growing interest in the search for alternative solutions that can prevent and / or reduce the risk of transmission of infectious and parasitic diseases in healthy fish populations. There are several existing herbal sources that deserve to be studied due to their potential beneficial effects and one of them is the garlic extract (Allium sativum). Although there is evidence of the benefits of using garlic extract in aquaculture, there are few studies on the effects of this extract on native species such as R. quelen. In Brazil, there are several species of parasites that can damage fishes, however protozoan represent one of the most damaging group of microorganisms to fish farming. In this context, one of the limiting factors in the cultivation of Rhamdia sp. is the presence of the ciliated protozoan Ichthyophthirius multifiliis, mainly in the stage of raising, which causes the disease known as ichthyophytyiasis, also known as white dot disease or ictio. The objective of this study was to evaluate the effect of dietary supplementation with garlic extract (Allium sativum) on the physiology, hematological, immune and metabolic systems of silver catfish (Rhamdia quelen) and the animal?s resistance to the parasite Ichthyophthirius multifiliis under controlled conditions in the laboratory. A total of 80 R. quelen, distributed in eight aquariums with 10 fish each one, were fed twice daily with diets containing 0%, 0.5%, 2.5% and 5% of dry garlic extract. After 77 days of feeding supplemented with garlic extract, half of the animals (n = 10) of each treatment and the control group were submitted to the challenge with the parasite Ichthyophthirius multifiliis, maintaining the feed supplemented. The other half of the animals (n = 10) of the treatments and control groups were maintained in the original circulation system receiving dietary supplementation. The use of garlic extract in the diet did not promote significant changes in glycemia, hepatic glycogen content, tissue and plasma aminotransferases activities, and tissue lipid peroxidation levels. On the other hand, it stimulated the synthesis of muscle glycogen and promoted a reduction of hepatic catalase activity. In terms of hematological and immune systems, the use of garlic extract increased the number of red blood cells but reduced hemoglobin content. Furthermore, it was not able to change the total number of leukocytes and thrombocytes, but it promoted an increase in the number of basophils and reduced the monocyte count of the animals. Also, the garlic supplemented diets were not able to change the plasma lysozyme and nitrite/nitrate levels. It can be concluded that dietary supplementation with garlic extract does not influence the basal metabolic homeostasis of the animals. Furthermore, garlic extract did not act as a growth promoter for silver catfish juveniles and did not promote changes in the basal immune or hematological response capacities of the fishes and did not improve the resistance to the infestation with the I. multifiliis. Still, there are few studies regarding the use of garlic in the diet, especially to R. quelen, reinforcing that further studies are necessary involving doses, treatment periods and different stages of animals?s development to adequately characterize the effects of garlic on metabolism, hematological and immune systems of silver catfish and its ability to react to diverse pathogens such as parasites and bacteria.Considerando o cultivo comercial de peixes, diferentes esp?cies v?m sendo produzidas de forma cada vez mais intensiva, ou seja, com altas densidades de estocagem/m? de ?gua. Este tipo de cultivo promove condi??es extremamente estressantes aos animais que podem causar dist?rbios em seu estado fisiol?gico levando ? redu??o do ganho de peso e crescimento, desempenho na reprodu??o e baixa resist?ncia a pat?genos, ficando suscept?veis ao ataque de parasitas, bact?rias, v?rus e/ou fungos. Diante disso, existe um crescente interesse na busca de solu??es alternativas direcionadas ? preven??o e/ou ? diminui??o do risco de transmiss?o de doen?as infecciosas e parasit?rias nas popula??es de peixes saud?veis. S?o v?rias as fontes fitoter?picas existentes e que merecem ser estudadas devido aos seus efeitos ben?ficos j? conhecidos e uma delas ? o extrato de alho (Allium sativum). Embora haja evid?ncias dos benef?cios do uso do extrato de alho na aquicultura, existem poucos estudos sobre os efeitos deste extrato em esp?cies nativas, como por exemplo o R. quelen. Existem no Brasil in?meras esp?cies de parasitas que causam danos aos peixes, no entanto os protozo?rios representam um dos grupos de microrganismos que mais causam preju?zos ? piscicultura. Neste contexto, um dos fatores limitantes no cultivo do g?nero Rhamdia ? a presen?a do protozo?rio ciliado Ichthyophthirius multifiliis, principalmente na fase de alevinagem, o qual ocasiona a doen?a conhecida como ictioftir?ase, tamb?m conhecida como doen?a dos pontos brancos ou ictio. O presente trabalho teve como objetivo avaliar o efeito da suplementa??o da ra??o com extrato de alho (Allium sativum) sobre a fisiologia, o sistema hematol?gico, imune e metab?lico de Jundi?s (Rhamdia quelen) e na resist?ncia de animais submetidos ao desafio com o parasita Ichthyophthirius multifiliis em condi??es controladas em laborat?rio. Foram utilizados 80 alevinos de R. quelen, distribu?dos em oito aqu?rios com 10 peixes cada, os mesmos foram alimentados duas vezes ao dia com dietas contendo 0%, 0,5%, 2,5% e 5% de extrato seco de alho. Ap?s 77 dias de alimenta??o suplementada com extrato de alho, metade dos animais (n = 10) de cada grupo de tratamento e controle foram submetidos ao desafio com o parasita Ichthyophthirius multifiliis, mantendo a ra??o suplementada. A outra metade dos animais (n = 10) dos grupos de tratamento e controle foi mantida no sistema de circula??o original recebendo a suplementa??o diet?tica. O uso do extrato de alho na ra??o n?o promoveu altera??es significativas na glicemia, conte?do de glicog?nio hep?tico, atividades das aminotransferases teciduais e plasm?ticas e nos n?veis de peroxida??o lip?dica tecidual. Por outro lado, estimulou a s?ntese de glicog?nio muscular e promoveu redu??o da atividade da catalase hep?tica. Em termos de avalia??o hemat?logica e imune, o uso do extrato de alho aumentou o n?mero de hem?cias, mas reduziu o conte?do de hemoglobina. Ainda, n?o foi capaz de alterar o n?mero total de leuc?citos e tromb?citos, mas promoveu aumento do n?mero de bas?filos e reduziu a contagem de mon?citos dos animais. Al?m disso, n?o promoveu altera??es nos conte?dos de lisozima e nitrito/nitrato plasm?ticos. Pode-se concluir que a suplementa??o da dieta com extrato de alho na ra??o n?o influencia na homeostasia metab?lica basal dos animais. Ainda, o extrato de alho n?o atuou como promotor de crescimento para os juvenis de jundi? e n?o promoveu altera??es na capacidade de resposta imune ou hemtal?gica basal dos peixes, n?o melhorando a resist?ncia frente ? infesta??o com o parasita I. multifiliis. Ainda existem poucos estudos em rela??o ao uso do alho na ra??o, em especial com o R. quelen, ressaltando a necessidade de mais pesquisas envolvendo doses, tempos de tratamento e diferentes fases de desenvolvimento para caracterizar adequadamente os efeitos do alho no metabolismo, no sistema imune do jundi? e na sua capacidade de resposta frente ? agentes patog?nicos diversos como parasitas e bact?rias