Impact of an immunostimulant diet and constant temperature on liver carbohydrate metabolism in the gilthead seabream Sparus aurata Linnaeus, 1758

The impact of an immunostimulant diet -frequently used to avoid winter syndrome in aquaculture- on liver carbohydrate metabolism was assessed over a period of 230 days in the gilthead sea bream Sparus aurata L., 1758. An enhancement of liver glycolytic, glycogenolytic and gluconeogenic potential in fish fed with immunostimulant diet was found, compared to a control group, suggesting an increase in liver metabolic activity. Moreover, immunostimulant-treated fish also showed higher values of lysozyme activity, along with a decrease in mortality, suggesting an increase in the nonspecific defence mechanism. The group kept at a 20°C constant temperature maintained appetite at normal levels, avoiding possible winter syndrome and obtaining better values for the production parameters studied (final weight, weight gain and mortality), compared with the control group.Se ha estudiado el efecto de una dieta inmunoestimuladora, usada frecuentemente en acuicultura para mitigar los efectos de la denominada enfermedad de invierno, y del mantenimiento a temperatura constante sobre el metabolismo hepático, los niveles de lisozimas y la mortalidad en dorada Sparus aurata L., 1758. El experimento se desarrolló durante un periodo de 230 días, observándose un incremento en los potenciales glucolítico y glucogenolítico, así como en el potencial gluconeogénico en el hígado de los ejemplares alimentados con la dieta inmunoestimuladora en relación al grupo de control. Estos resultados sugieren un aumento de la actividad metabólica hepática derivada de la dieta inmunoestimuladora. Asimismo, se observaron valores más elevados de los niveles de lisozimas simultáneos a una reducción de la mortalidad en el grupo tratado con inmunoestimuladores, lo que induce a concluir que esta dieta enriquecida fortalecería los mecanismos defensivos inespecíficos, disminuyendo la mortalidad. En el grupo de permanencia a temperatura constante de 20ºC se consiguió mantener el apetito de los peces y, por tanto, favorecer la prevención del posible síndrome de invierno, obteniéndose mejores valores en las distintas variables de producción estudiadas (peso final, ganancia de peso y mortalidad) con respecto al grupo de control.Instituto Español de OceanografíaVersión de editor

Influence of vegetable diets on physiological and immune responses to thermal stress in Senegalese sole (Solea senegalensis)

The substitution of fish resources as ingredients for aquafeeds by those based on vegetable sources is needed to ensure aquaculture sustainability in the future. It is known that Senegalese sole (Solea senegalensis) accepts high dietary content of plant ingredients without altering growth or flesh quality parameters. However, scarce information is available regarding the long-term impact of vegetable diets (combining the inclusion of both vegetable protein and oils) on the stress response and immunity of this fish species. This study aims to evaluate the concomitant effect of the extended use of vegetable protein-based diets with fish oil (FO) replacement (0, 50 or 100%) by vegetable oils (VO), on the response to acute (10 min) or prolonged (4 days) stress, induced by thermal shock. Plasma levels of cortisol, glucose and lactate as well as hepatic levels of glucose, glycogen and lactate were evaluated as primary and secondary responses to stress, 6 and 18 months after feeding the experimental diets (6 and 18 MAF). The brain monoaminergic activity in telencephalon and hypothalamus, and non-specific immune parameters were also evaluated. As expected, thermal shock induced an increase in values of plasma parameters related to stress, which was more evident in acute than in prolonged stress. Stress also affected lactate levels in the liver and the values of the alternative complement pathway-ACH50 in the plasma. Dietary substitution of FO induced an effect per se on some parameters such as decreased hepatic glucose and glycogen levels and peroxidase activity in plasma as well enhanced serotonergic activity in brain of non-stressed fish. The results obtained in some parameters indicate that there is an interaction between the use of vegetable diets with the physiological response to thermal stress, as is the case of the hepatic lactate, serotonergic neurotransmission in brain, and the activity of ACH50 in plasma. These results suggest that the inclusion of VO in plant protein based diets point to a slightly inhibited stress response, more evident for an acute than a prolonged stress. © 2018 Conde-Sieira et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.This research was partially supported by the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT–Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020" to L.M.P.V, and by research a grant from Spanish Agencia Estatal de Investigacio´n and European Fund for Regional Development (AGL 2016-74857-C3-1-R and FEDER) to J.L.S. M.C-S. is supported by a postdoctoral grant from Xunta de Galicia (Plan I2C). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. There are no conflicts of interest in connection with the present study

Glucose metabolism in fish : a review

ReviewInternational audienc

Dietary protein/carbohydrate ratio in low-lipid diets for Senegalese sole (Solea senegalensis, Kaup 1858) juveniles. Influence on growth performance, nutrient utilization and flesh quality

Four isoenergetic (21 kJ/g dry matter, DM) and isolipidic (65 g/kg DM) diets containing different crude protein/total carbohydrate (CHO) ratios: 60/26, 56/30, 52/34 and 48/38, were tested in 22 g Senegalese sole for 104 days. Apparent digestibility coefficients (ADC) were not affected by the treatments, and all groups presented extremely low starch ADC values (22.8%\u201336.5%). Replacement of dietary protein by CHO did not affect daily growth index (0.9\u20131.0), but significantly increased voluntary feed intake of fish. Regression analyses demonstrated that digestible protein content, rather than digestible energy, was the main dietary factor influencing such feeding activity (R2 = .952). A significantly increased feed conversion ratio was observed in sole fed increasing CHO contents. The dietary protein/CHO ratio did not influence whole-body composition. Sole fed the 48/38 diet showed the lowest efficiency in terms of N and energy utilization. PUFA were the most represented fatty acid fraction in fillet, regardless of the dietary protein/CHO ratio, mainly due to the high content of DHA. Senegalese sole increase feed intake under low dietary protein/CHO ratios to ensure an adequate N intake. Such compensatory mechanism seems to be triggered to satisfy a specific protein metabolic requirement for energy purposes as tissue accretion remained unchanged