The efficiency of a recirculation system for the cultivation of C. auratus, fed with natural and artificial diets was evaluated. The experiment consisted of four treatments with four replicates. The first two treatments used recirculation system and the last two static system. In the first and fourth treatment, animals were fed with brine shrimp biomass (50% CP), while in the second and third treatments a commercial flake ration (42% CP) was used. At the end of cultivation (60 days), water samples were taken from all experimental units and subjected to standard plate count for determining the density of mesophilic bacteria. Final weight (g), final length (cm), specific growth rate (% day -1) and weight gain (%) were significantly different (p<0.05) among tested diets, but the culture systems did not affect fish performance. There was significant difference (p<0.05) between systems for total ammonia and nitrite. Animals fed with brine shrimp biomass acquired more intense and brighter colors than those fed only with commercial flake food. The values of standard plate count of mesophilic bacteria ranged from 7.0 × 10³ to 1.1 × 10(4) CFU.ml-1. In this study we observed that C. auratus is a species tolerant to adverse water conditions, perhaps with increased stock densities, the recirculation system could play some positive role on the zootechnical performance of cultured animals.

A eficiência de um sistema de recirculação para o cultivo de C. auratus, alimentados com dieta natural e artificial foi avaliada. O experimento consistiu de quatro tratamentos com quatro repetições. Os dois primeiros tratamentos utilizaram sistemas de recirculação e os dois últimos sistemas estáticos. No primeiro e quarto tratamento, os animais foram alimentados com biomassa de artêmia (PB 50%), enquanto nos tratamentos dois e três, com ração comercial em flocos (42% PB). Ao final do cultivo (60 dias), amostras de água foram coletadas em todas as unidades experimentais e submetidos a contagem padrão em placas para determinação da densidade de bactérias mesófilas. O peso final (g), comprimento final (cm), taxa de crescimento específico (% dia-1) e ganho de peso (%) foram significativamente diferentes (p<0,05) entre as dietas testadas, mas os sistemas de cultivo não afetaram o desempenho dos peixes. Houve diferença significativa (p<0,05) entre os sistemas para os níveis de amônia total e nitrito. Os animais alimentados com biomassa artêmia adquiriram cor e brilho mais intensos do que aqueles alimentados apenas com ração comercial em flocos. Os valores de contagem padrão em placas de bactérias mesófilas variaram de 7,0 × 10³ para 1,1 × 10(4) CFU.ml-1. Neste estudo, observou-se que C. auratus é uma espécie tolerante a condições adversas de água, talvez com maior densidade de estocagem, o sistema de recirculação poderia desempenhar papel positivo sobre o desempenho zootécnico dos animais cultivados. | The efficiency of a recirculation system for the cultivation of C. auratus, fed with natural and artificial diets was evaluated. The experiment consisted of four treatments with four replicates. The first two treatments used recirculation system and the last two static system. In the first and fourth treatment, animals were fed with brine shrimp biomass (50% CP), while in the second and third treatments a commercial flake ration (42% CP) was used. At the end of cultivation (60 days), water samples were taken from all experimental units and subjected to standard plate count for determining the density of mesophilic bacteria. Final weight (g), final length (cm), specific growth rate (% day -1) and weight gain (%) were significantly different (p<0.05) among tested diets, but the culture systems did not affect fish performance. There was significant difference (p<0.05) between systems for total ammonia and nitrite. Animals fed with brine shrimp biomass acquired more intense and brighter colors than those fed only with commercial flake food. The values of standard plate count of mesophilic bacteria ranged from 7.0 × 10³ to 1.1 × 10(4) CFU.ml-1. In this study we observed that C. auratus is a species tolerant to adverse water conditions, perhaps with increased stock densities, the recirculation system could play some positive role on the zootechnical performance of cultured animals.

This study investigates the impact of different diets on fish growth and bacterial community structure present in the intestine of goldfish (<i>Carassius auratus</i>) and their aquaculture water under recirculating water conditions. We assumed that different types of diet would form different intestinal microbiota that may affect host growth. Using Illumina MiSeq high-throughput sequencing, we analyzed bacterial communities in goldfish fed with formulated pellet feed, Tubifex worms (<i>Limnodrilus hoffmeisteri</i>), and an alternating diet of both. Over a 14-day feeding trial, no significant differences in juvenile goldfish growth were observed between groups. After 7 days, diet changes significantly influenced the abundance and diversity of intestinal bacteria, with the alternating diet notably enhancing bacterial diversity in both the intestines and water. However, these differences in bacterial diversity decreased by day 14. The results indicate that diet type affects microbial community diversity in the intestines and water of goldfish, and that goldfish intestines maintain a stable core bacterial community structure. This highlights the potential for optimizing diet types to enhance microbial health and stability in aquaculture systems and, in addition, provides an important scientific basis for alternative diets in goldfish aquaculture in the industry.