Effect of fixed feeding time on growth, body composition, and hepatic histology of hybrid catfish (Pseudoplatystoma reticulatum x Leiarius marmoratus) fed with carbohydrates and lipids ratios

Background: feed and light are the most important factors affecting the biological rhythms of fish. This work studies fish adaptation to those factors. Objetive: to determine the influence of feeding time and dietary starch and lipid levels on growth, body composition, and liver histology of hybridized Brazilian catfish. Methods: two isoenergetic diets were formulated to contain two levels of crude starch (CHO, %) and lipids (L, %): 5/11 CHO/L and 25/2.2 CHO/L. Sixty animals (260 ± 10 g) were randomly distributed into twelve tanks (100 L). Using self-feeders, two fish groups were fed a diet containing either 5% or 25% starch during the light period (ML), while other two groups were fed the same diets during the dark period (MD). The following parameters were measured: final weight, weight gain, specific growth rate, food intake, hepatosomatic index, and viscerasomatic index. The experiment was carried out in triplicate for 60 days. Results: growth parameters such as specific growth rate (SGR), final weight, and weight gain showed statistical differences between groups, with the best results for the group fed the 25% starch diet during ML. Significant differences between groups on body lipid content, energy, and dry weight were also recorded for those feed 25% starch in the MD. A significant effect was also observed on liver lipid and glycogen content, with values generally higher for ML with 5% starch. Fish fed 25% starch showed significantly lowest lipid and glycogen content during ML. Surprisingly, the opposite occurred regarding liver composition for fish fed in MD. Conclusions: we suggest diurnal feeding should be practiced for optimal performance of juvenile fish, however dark or light phases could be used, taking into consideration its relationship with carbohydrate levels. Antecedentes: alimentos e luz são os fatores mais importantes que arrastam os ritmos biológicos em peixes. Neste trabalho, trazemos um pouco do conhecimento sobre a plasticidade dos peixes para a utilização dos alimentos. Objetivo: este estudo foi realizado para determinar a influencia do horário de alimentação e níveis de amido e lipídio dietético no crescimento, composição corporal e histologia hepática em um bagre hibrido. Métodos: duas dietas isoenergéticas foram formuladas para conter dois níveis de amido (CHO, %) e lipídeo (L, %): 5/11 CHO/L e 25/2.2 CHO/L. Sessenta animais (260 ± 10 g) foram distribuídos aleatoriamente em 12 tanques (100 L). Um grupo de peixes foi alimentad