Dietary Supplementation with Fumaric Acid Improves Growth Performance in Nile Tilapia Juveniles.

Organic acids have recently been identified as promising replacements for antibiotics in aquafeeds that promote fish growth and feed efficiency. This study evaluated the inclusion of fumaric acid (FA; 0, 5, 10, 15, 20, and 30 g/kg) in diets (350 g/kg CP; 3.4 kcal digestible energy/g) of Nile tilapia juveniles. Fish (average weight 1.7 ± 0.1 g) were distributed in three 40 L aquaria per treatment (13 fish/aquaria) in a completely randomized design. Over 35 days, the fish received the experimental diets three times daily to apparent satiety. The maximum weight gain, feed efficiency ratio, and protein efficiency ratio were recorded in fish supplemented with 14-15 g/kg FA. After 28 days, Enterobacteriaceae was registered only in the gut of tilapia without FA augmentation. Gram-negative bacteria in the fish gut decreased (p < 0.05) in fish receiving 17 g/kg of dietary FA, increased after this level. The intestinal villi height and width were affected (p < 0.05) by FA levels and feeding time. Thus, inclusion of 15 g/kg of FA was effective in promoting growth, improving intestinal morphometry, and decreasing negative gut bacteria of Nile tilapia juveniles after 35 days.

Effects of dietary Bacillus subtilis and Shewanella algae in expression profile of immune-related genes from hemolymph of Litopenaeus vannamei challenged with Vibrio parahaemolyticus.

B. subtilis and S. algae effects in growth, survival and innate immunity were assessed on L. vannamei juveniles. During 60 days, shrimp were reared in three treatments: Bs, fed with 106 CFU of B. subtilis per gram of commercial feed, Sa, fed with 106 CFU of S. algae per gram of commercial feed and Control (without bacterial addition). Then, the animals were subjected to a V. parahaemolyticus challenge. For this purpose, four treatments were established: Control (shrimp not submitted to probiotic treatments), Vibrio (Vibrio challenged shrimp), Vibrio + Bs (Bs challenged shrimp) and Vibrio + Sa (Sa challenged shrimp). Shrimp hemolymph was sampled 45-days after rearing and 24 h post-challenge for quantification of prophenoloxidase (proPO), lipopolysaccharide and ß-1,3-glucan-binding protein (LGBP) and hemocyanin (HEM) transcripts by qPCR. Moreover, shrimp final weight and survival were also verified. B. subtilis administration enhanced shrimp growth and improved proPO, LGBP and HEM expression levels before and after challenge. After 60-days of feeding, Sa final weight was higher than the Control, whereas Vibrio + Sa cumulative mortality after 48 h of Vibrio challenge was lower than Vibrio group. These results could be correlated with the proPO and LGBP up regulation in Vibrio + Sa compared to Vibrio group, protecting L. vannamei from the bacterial infection. Together, these results suggest the probiotic potential of B. subtilis e S. algae in the modulation of immune-related genes as a tool to control V. parahaemolyticus infection inside shrimp.

Detecção de Aeromonas spp. e do gene de virulência aerolisina em tilápias do Nilo (Oreochromis niloticus) com a técnica de mPCR / Detection of Aeromonas spp. and virulence gene aerolysin in Nile tilapia (Oreochromis niloticus) using PCR technique

As infecções causadas por bactérias do gênero Aeromonas estão entre as doenças mais comuns em peixes cultivados em todo o mundo, com ocorrência de aeromoniose em todos os países que possuem cultivo de tilápia do Nilo (Oreochromis niloticus). O presente trabalho descreve o desenvolvimento de uma nova multiplex PCR (mPCR) para diagnóstico de Aeromonas spp. e identificação do gene aerolisina (aerA). Para padronização da mPCR foram utilizadas cepas de referência de várias espécies do gênero Aeromonas e de outros gêneros. Também foram usadas cepas de campo de A. hydrophila oriundas de cultivos de peixes pacamãs (Lophiosilurus alexandri) e Aeromonas spp. de tilápias do Nilo. Os primers foram desenhados com base na região 16S rRNA e aerA. Para verificar a melhor temperatura de anelamento foram utilizados gradientes entre 59°C a 61°C com 40ng de DNA molde. Os produtos da amplificação da região 16S rRNA e do gene aerA apresentaram 786 e 550pb, respectivamente. A mPCR apresentou melhor temperatura de anelamento a 57,6°C com limite de detecção das concentrações de DNA em ambos genes (16S rRNA and aerA) de 10-10g/μL. A mPCR padronizada é rápida, sensível e específica no diagnóstico de Aeromonas spp. e identificação do gene aerolisina. Esta metodologia apresenta vantagens quando comparada aos métodos de diagnóstico convencionais, podendo ser utilizada em cultivos comerciais de tilápias do Nilo ou outros peixes. A identificação do gene aerolisina é uma importante ferramenta na determinação do potencial patogênico dos isolados de Aeromonas spp. estudados.(AU)

Infections caused by bacteria of the genus Aeromonas are among the most common diseases in fish farming systems worldwide, and this disease occurs in all countries which have Nile tilapia (Oreochromis niloticus) farmed. The present work describes the development of a new multiplex PCR (mPCR) technique that diagnosis the genus Aeromonas and detects aerolysin gene (aerA). Reference strains of several Aeromonas species and other genera were used for standardization of mPCR. Strains of A. hydrophila from "pacaman" fish (Lophiosilurus alexandri) and Aeromonas spp. from Nile tilapia from farming systems were used too. Primers were designed based on the 16S rRNA region and aerA (aerolysin toxin). To verify a better annealing temperature were used gradients between 59°C and 61°C with 40ng of the DNA template. The 16S rRNA gene and the aerA gene amplification products showed 786 and 550 bp, respectively. The mPCR showed better annealing temperature at 57.6°C, and the detection limit for both genes (16S rRNA and aerA) was 10-10g/μL of the DNA. The standardized mPCR is quick, sensitive, and specific for Aeromonas spp. diagnosis and to detect aerolysin gene. This method showed advantages when compared to the conventional diagnostic methods and can be used in Nile tilapia or other fish farming systems. The detection of aerolysin gene is an important tool to determine the potential pathogenicity of Aeromonas spp. isolates.(AU)