Yinet Andrea Parrado-Sanabria’s research while affiliated with Universidad de Cádiz and other places

The effects of diet supplemented with Myrcia sylvatica essential oil (EOMS) on growth and stress tolerance to different stocking densities were assessed in Sparus aurata. Initially, three experimental groups were established: i) control, ii) 1.0 and iii) 2.0 mL EOMS kg dry feed-1. After 90 days, nine fish per group were anesthetized, weighed and sampled for metabolic analysis. The remaining fish were divided into two different conditions: low (LD - 5 kg m-3) and high (HD - 40 kg m-3) stocking densities, constituting a final experimental setup with six treatments. After 22 days, 10 individuals per treatment were anesthetized and sampled for biochemical analysis. EOMS feeding for 90 days did not interfere with growth, although it was effective in reducing cortisol levels and the activation of lipid and carbohydrate metabolism. The HD interfered in growth performance, increased the lactate levels in the control group, reducing also hepatic glycogen levels without dependence on diet supplementation. The 2.0 mL EOMS + LD group increased the growth parameters and decreased the cortisol and triglycerides levels. Additionally, metabolism adjustment was observed to provide energy during LD and HD conditions, indicating that diets supplemented with EOMS produce metabolic reorganization to maintain body homeostasis, suggesting its use as a beneficial supplement in fish.

Aquaculture activities promote stress situations that decrease fish welfare. In this sense, the objective of this study was to evaluate the effects of adding essential oil of Myrcia sylvatica (EOMS), a substance that has been used to mitigate activation of stress system in other teleost, in the diet of gilthead sea bream (Sparus aurata). Juveniles specimens were provided by the Servicios Centrales de Investigación de Cultivos Marinos (SCICM, University of Cadiz), acclimated for one month in 1000 L-tanks and distributed in 9 tanks of 80 L (initial stocking density: 2.76 ± 0.013 g/L), which constituted the three experimental groups in triplicate: i) control, ii) 1.0 mL EOMS/kg food, and iii) 2.0 mL EOMS/kg food). After 90 days, fish (n = 9 fish per group) were anesthetized measured and weighed. Subsequently, blood and liver samples were extracted for cortisol and metabolites analysis. The addition of EOMS in diet decreased plasma cortisol levels and plasma triglycerides, as well as liver glycogen. Therefore, our results suggest that the addition of EOMS in the diet (doses between 1.0-2.0 mL EOMS/kg food) could promote fish welfare of this specie in culture.

Inadequate stocking densities (e.g. high stocking density) activated stress system, affecting the metabolism of lipids, carbohydrates and proteins. The aim of this study was to evaluate the effects of adding essential oil of Myrcia sylvatica (EOMS) in the diet of Sparus aurata juveniles held at different stocking densities. Juvenile specimens were distributed into the three experimental groups, feeding three different diets during three additional months: i) control, ii) 1.0 mL EOMS/kg of feed, and iii) 2.0 mL EOMS/kg feed. After that, each experimental group was divided in two different conditions: low and high stocking densities (LD-5 kg/m3 and HD-40 kg/m3, respectively) constituting a total of six different treatments: i) control-LD, ii) control-HD, iii) 1.0 mL-LD, iv) 1.0 mL-HD, v) 2.0 mL-LD, and vi) 2.0 mL-HD). After 22 days under these conditions, 10 individuals from each treatment were anesthetized and sampled for plasma and liver. These samples were analysed for cortisol and metabolites analysis. Our results shown that EOMS decreased plasma cortisol levels under LD and HD conditions. Moreover, it is observed that diets supplemented with 2.0 mL EOMS/kg of food originates a metabolic reorganization to cope with the stressful situation produced by higher stocking densities.