Effect of starvation and re-feeding on reproductive indices, body weight, plasma metabolites and oxidative enzymes of sea bass ( Dicentrarchus labrax)

Abstract

Feed management is an important factor for successful aquaculture, especially when it affects gonad maturation. In this context, the present study evaluates the effects of long term starvation (1F–3S: one-month feeding – three-month starvation) and starvation/re-feeding (2S–2F: two-month starvation – two-month re-feeding) on gonad maturation, hematological/biochemical indices and proximate composition of liver and muscle of vitelogenic sea bass. In males, all the fish in the control group (4F–0S: four-month feeding – zero-month starvation) reached the maturity stage S2 (Mature), while only 33% and 75% reached that stage in the 1F–3S and 2S–2F groups, respectively. In females, the percentages of immature gonads were 80%, 25% and 50% for the groups 1F–3S, 2S–2F and 4F–0S respectively, while the percentages of the fish which reached the stage of vitellogenesis were 20%, 75% and 50% for the same groups. The concentration of glucose and lactate in plasma was not affected by starvation or re-feeding. On the contrary, triglycerides, phospholipids and total lipids of group 1F–3S decreased significantly, whereas cholesterol did not differ compared to the control group. In the 2S–2F group, total lipids and cholesterol were also significantly decreased while triglycerides and phospholipids were not altered. Proximate composition analysis in the liver showed that long term starvation (1F–3S) led to a significant reduction of crude lipid and ash, compared to the 4F–0S and 2S–2F groups. In contrast, crude protein concentration in the liver was significantly increased in 1F–3S group compared to 4F–0S and 2S–2F groups. In white muscle a significant reduction of crude lipids was detected in the 1F–3S and 2S–2F groups, while no significant changes were observed in crude protein, ash and moisture concentrations. The enzymatic activities of lactate dehydrogenase (L-LDH), citrate synthase (CS) and 3-hydroxyacyl CoA dehydrogenase (HOAD) were significantly increased in the liver of 1F–3S fish, whereas in red muscle both HOAD and CS were significantly decreased in both 1F–3S and 2S–2F groups. Overall our results indicate that a 2 month starvation and 2 month re-feeding period during vitellogenesis reduces GSI and maturity stage in male sea bass and affect the levels of biochemical blood indices and the activities of certain enzymes of the intermediary metabolism.