MICROALGAE UTILIZATION IN FIRST FEEDING DIETS FOR GILTHEAD
SEABREAM (Sparus aurata): INFLUENCE ON ANTIOXIDANT STATUS.
1 V.C. Rubio, 1 M. Arizcun, 2 A. Vizcaíno, 3 R, García-Cubero and 1 E. Abellan.
1 IEO, Planta de cultivos marinos de Mazarrón, 30860 – Puerto de Mazarrón, Murcia (Spain).
2 Dpto. Biología y Geología. Universidad de Almería-CEIA, 04120 – Almería (Spain).
3 Algaenergy S.A. Parque Empresarial “La Moraleja”. 28108 – Alcobendas, Madrid (Spain).
E-mail: emilia.abellan@mu.ieo.es
Introduction
Algae possess a high antioxidant activity, mainly due to its polyphenols content which acts as free radical scavengers, stabilizing the compounds obtained from free radicals, increasing or maintaining the endogenous antioxidant defence and inhibiting pro-oxidant enzymes. Therefore, algae are very promising candidates for use as antioxidants in aquaculture as a strategy to increase the welfare, growth and survival during different growth stages of fish. However, there is not information on the effect exerted by the dietary algae inclusion on the antioxidant status during their early stages of development.
Materials and method
Gilthead seabream of 43 dph were randomly distributed into 18 tanks (10 larvae/l) and fed with six isoproteic and isoenergetic diets: control commercial, control experimental without microalgae, T 5%, T 10% (supplemented with 5% and 10% of Tetraselmis suecica respectively), I 5%, I 10% (supplemented with 5% and 10% of Isochrysis galbana respectively). The study was conducted at standard conditions. The fish were sampled at the end of the experiment (98 dph). All measurements and determinations were performed in six juvenile fish (n=6/treatment) and in six to ten pooled livers
(n=6/diet). The antioxidant defence was determined by measuring key enzymes: CAT,
SOD, GPx and GR. Lipid-peroxidation levels were determined based on malondialdehyde (MDA) levels generated by oxidation of polyunsaturated fatty acids.
Differences between means due to diet composition were analyzed by using a one-way
ANOVA ( P <0·05), means were compared using Tukey’s test.
Results
The addition of microalgae to the diet reduces lipid peroxidation compared to the commercial feed (Figure 1), however, not significantly influence the activity of the main antioxidant enzymes in whole fish (Table 1).
Comercial Control
Figure 1.
Effect of dietary treatment on lipid peroxidation of whole fish and pools of liver (n=6). Different superscript are significantly different ( P <0.05)

When the liver was analyzed, a trend to decreased oxidative stress in fish fed diets enriched with microalgae 5% (Figure 1) was observed, although were not statistically significant. This tendency to reduce lipid peroxidation was supported by a statistically significant increase in the activity of the enzymes CAT and SOD in the liver of fish
(Table 1), but did not modify the activity of GPx and GR.
Table 1.
Enzymatic activity of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) of gilthead seabream juveniles fed with six experimental diets (mean ± standard error, n=6).
Dieta
Whole fish
Commercial
Control
T 5%
I 5%
T 10%
I 10%
Pooled livers
Commercial
CAT
(U/mg prot)
254.4 ± 7.3
235.8 ± 25.1
260.3 ± 18.8
253.5 ± 12.7
257.8 ± 4.7
295.2 ± 26.0
SOD
(U/mg prot)
183.50 ± 7.80
217.80 ± 17.71
159.83 ± 13.92
166.84 ± 28.60
185.33 ± 23.59
203.11 ± 19.61
GPx
(mU/mg prot)
147.21 ± 4.56
156.92 ± 5.89
138.55 ± 9.05
148.23 ± 5.89
137.77 ± 9.98
146.96 ± 5.77
GR
(mU/mg prot)
18.04 ± 2.02
15.79 ± 0.57
17.21 ± 1.24
18.86 ± 2.04
17.67 ± 1.26
17.39 ± 1.12
Control
T 5%
I 5%
T 10%
I 10%
262.7 ± 3.1
ab
206.0 ± 15.4
bc
285.3 ± 30.7
a
246.9 ± 43.5
abc
190.2
± 21.7
c
292.3 ± 22.1
a
79.0 ± 3.1
ab
87.5 ± 1.1
bc
100.0 ± 4.5
d
94.8 ± 4.1
cd
75.3 ± 1.0
a
74.7 ± 2.1
a
139.5 ± 5.8
141.0 ± 4.8
161.7 ± 8.9
143.5 ± 4.1
155.4 ± 16.3
150.2 ± 16.4
29.1 ± 2.1
29.1 ± 1.5
24.2 ± 4.9
19.7 ± 3.2
23.7 ± 2.4
32.5 ± 3.5
Means not sharing a common superscript letter are significantly different ( P <0.05)
Discussion and conclusion
Diets supplemented with 5% of microalgae significantly decreased lipid peroxidation in whole fish compared to the commercial feed or what is the same, the reduction of oxidative stress is substantial compared to the commercial diet usually employed in the production of gilthead seabream.
The absence of a pronounced enhancement of the antioxidant defence system (enzymatic system) in whole fish does not imply that the addition of microalgae to diet not produce a positive effect in reducing oxidative stress, since the diet enriched with microalgae could exert this effect through potentiation of non-enzymatic defence system, as freeradicals scavenger or increasing the enzymatic antioxidant activity in target organs as support the results obtained in liver (Figure 1).
Further studies would be needed to determine what should be the most appropriate percentage of inclusion of microalgae in the diet in order to achieve a significant reduction of oxidative stress and consequently obtain improved fish welfare and optimize commercial production.
Therefore, we can conclude that the addition of 5% of microalgae to diet reduces lipid peroxidation of the fish, at least inducing an increased antioxidant activity of the CAT and SOD in liver.
Acknowledgements
This study was supported by Algaenergy S.A.