Introduction:
Halophyte plants such as Salicornia ramosissima have the ability to grown in saline soils (marginal land) and/or be irrigated with seawater. Despite t he green tips of Salicornia are sold as food, the woody part is still considered a residue. However, this residue biomass is rich in valuable bio-active molecules that can be extracted using simple and affordable processing1,2 . These compounds include hydroxycinnamic acids that may present strong antinflammatory and antioxidant effects. The present study aimed to assess the effects of Salicornia ramosissima biomass inclusion in diets for European seabass Dicentrarchus labrax . Fish immune condition during the feeding trial and the inflammatory response to inact ivated Photobacterium damselae subsp. piscicida (Phdp ) were evaluated.
Material and methods:
European seabass juveniles (mean initial weight: 7.26 ± 0.06 g) were reared at Riasearch Lda. facilities (Murtosa , Portugal). Fish were randomly distributed by 12 tanks of 350 L with 80 individuals allocated to each tank. Four diets were tested in triplicates. A commercial like diet was used as control (CTRL) whereas three experimental diets including S. ramosissima biomasses were formulated to have similar proximal compositions to CTRL. In the experimental diets, whole plant biomasses of S. ramosissima were included at three different levels: 2.5, 5 and 10% of feed (ST2.5, ST5 and ST10, respectively) and fish were given 3 meals per day, by hand until visual satiety for 62 days . To evaluate seabass immune condition, blood, plasma and head- kidney were collected from 5 fish per tank on d ay 34 and 62 for haematological and immune condition assessment and gene expression analysis. At the end of the feeding trial, fish were subjected to an inflammatory challenge by intraperitoneal injection with an inactivated Phdp (strain PP3). Blood, plasma, peritoneal cells and head-kidney samples were collected from 3 fish per tank at 4, 24, 48 and 72 hours after injection. The sampling point 62 days was used as time 0 h during the time-course study, as they represent unstimulated animals prior to inflammation.
Results and discussion:
No changes were observed among dietary treatments after both 34 and 62 days of feeding on the haematological profile. Similarly, no changes were observed among dietary treatments after both 34 and 62 days on the plasma humoral immune parameters analysed (peroxidase, anti-protease and bactericidal activities and lysozyme). However, in response to inflammation, f ish fed ST5 showed a decrease of hematocrit and mean corpuscular values compared to those fed CTRL and ST10, respectively. Also, 4 hours after the inflammatory stimulus, seabass fed ST10 presented a higher concentration of leucocytes found in the peritoneal cavity in response to local inflammation (Figure 1) compared to fish fed CTRL. Head-kidney gene expression is being performed in fish sampled for all treatments and sampled times .
Acknowledgements: This work was supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 86283 (project AQUACOMBINE). This output reflects the views only of the authors, and the European Union cannot be held responsible for any use which may be made of the information contained therein. BC w as supported by FCT - Foundation for Science and Technology (IF/00197/2015).
1 Parvaiz A. and Satyawati S. (2008) Plant, Soil and Environment 54: 89–99.
2 Stuchlık M. and Zak S. (2002) Biomedical Papers 146: 3–10.