The present work aimed to evaluate whether the use of chromic oxide (Cr 2 O 3 ) as dietary inert marker in fish digestibility studies interferes with gut microbial community modulation and gut morphology. To assess the effects of Cr 2 O 3 under potential diverse microbiota populations, dietary Cr 2 O 3 was tested using challenging plant feedstuffs (PF)-based diets supplemented or not with prebiotics, as prebiotics are expected to modify gut microbiota populations. For that purpose, three diets were formulated to include circa 20:80 fish meal and PF as protein sources, without (CTR) or with prebiotic supplementation (10 g/kg XOS or GOS). These diets did not include Cr 2 O 3 (ÀCr 2 O 3 diets). Three similar additional diets were formulated to include 5 g/kg Cr 2 O 3 (+Cr 2 O 3 diets). Cr 2 O 3 effects on gut microbiota were assessed for the first time in the allochthonous (digesta) and autochthonous (mucosa) community by a culture-independent molecular approach, using denaturing gradient gel electrophoresis (DGGE). No differences in gut bacterial profiles (number of operational taxonomic units, microbiota richness, diversity and similarity indices) were observed between dietary treatments. No significant alterations in submucosa layer structure, enterocytes and eosinophilic granular cells structure, goblet cells and leucocytes quantity were detected in the distal intestine among diets. In conclusion, data indicate that dietary inclusion of 5 g/kg Cr 2 O 3 does not interfere with gilthead sea bream (Sparus aurata) gut microbiota and gut morphology, suggesting that a dietary incorporation level of 5 g/kg Cr 2 O 3 can safely be used as inert marker in digestibility studies.
The performance and hematologic responses of juvenile piavuçu fish (Leporinus macrocephalus) that were fed with feeds containing garlic, cinnamon, and yeast before being submitted to stress from capture were evaluated. The experiment was conducted in the Fish Nutrition Laboratory (Laboratório de Alimentação e Nutrição de Peixes), where 192 piavuçu juveniles (3.09 ± 0.8 g) were distributed among 16 tanks (170 L), with a density of 12 fish per tank. The experiment consisted of four treatments and four repetitions. Treatments included the addition of 10 g Kg -1 garlic, 10 g Kg -1 cinnamon, and 9x10 5UFC g -1 of Saccharomyces cerevisiae yeast, in addition to a control diet that included no additives. The performance, body indices, and survival of the fish were evaluated. After the performance test, the fish were submitted to stress from capture, and the effect of the additives as a stress reducer was evaluated through hematologic analyses. Better weight gain and feed conversion ratios (P≤0.05) were observed in the fish fed with diets containing garlic and cinnamon; however, no alterations were noticed in the nutritional composition of fish carcasses, regardless of the treatment they were submitted to. A reduction in the number of leukocytes of the fish submitted to stress in all treatments was verified. It is possible to conclude that diets supplemented with garlic and cinnamon at the level of 10 g Kg -1 led to a better performance, while not influencing the hematologic standards after the stress from capture. canela e 9x10 5 UFC g -1 de levedura Saccharomyces cerevisiae e uma dieta controle, sem a inclusão de aditivo. Foram avaliados o desempenho, índices corporais e sobrevivência dos peixes. Após o ensaio de desempenho os peixes foram submetidos ao estresse de captura e o efeito dos aditivos como mitigador do estresse foi avaliado por meio de análises hematológicas. Observou-se melhor ganho de peso e conversão alimentar (P≤0,05) nos peixes alimentados com as dietas contendo alho e canela, porém não foram observadas alterações na composição bromatológica da carcaça em nenhum dos tratamentos. Verificou-se redução nos números de leucócitos dos peixes submetidos ao estresse em todos os tratamentos. Conclui-se que dietas suplementadas com alho e canela ao nível de 10 g Kg -1 apresentaram melhor desempenho, não influenciando nos parâmetros hematológicos após o estresse de captura.
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