No abstract

In the this study, we evaluated the effect of replacement of fish meal by a marine microalgae Spirulina platensis on growth, digestive enzyme activities, fatty acid composition and responses to ammonia and hypoxia stress in Pacific white shrimp Litopenaeus vannamei (2.6 ± 0.2 g). Experimental diets contained S. platensis at 0%, 25%, 50%, 75% and 100% replacement levels. After 8 weeks of feeding trial, growth parameters and proximate body composition were not significantly different among treatments (p > .05). Amylase and lipase activities did not show any significant differences between control group and other experimental diets (p > .05), while activities of trypsin and chymotrypsin were significantly higher in shrimp fed diet with 50% substitution of microalgae compared to control group. Fatty acid contents, particularly polyunsaturated fatty acids (PUFAs) including arachidonic acid (ARA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), were significantly higher in control diet compared to other experimental diets. On the contrary, the majority of fatty acids including the contents of PUFAs in the whole body of L. vannamei fed with different levels of S. platensis were significantly higher compared to those of control group. After 48‐h exposure to ammonia, survival per cent was not statistically different between all groups (p > .05), but in hypoxia challenge, the survival per cent of control group was significantly less than that of treatments fed diets contained S. platensis (p < .05). Altogether, our results demonstrated the effectiveness of S. platensis as a reliable protein source for substitution of fish meal in shrimp aquaculture.

This study was conducted to investigate the effectiveness of fish meal substitution by Chlorella vulgaris meal in the diet of Pacific white shrimp, Litopenaeus vannamei. Experimental diets contained varying levels of fish meal (400, 300, 200, 100 and 0 g/kg) which was replaced by increasing levels of C. vulgaris (0, 97.2, 194.4, 291.6 and 388.8 g/kg). After 8 weeks of feeding trial, shrimp fed diet with 97.2 g/kg C. vulgaris showed significantly improved growth compared to other treatments including control. Similarly, shrimp fed diet with 97.2 g/kg C. vulgaris showed significantly higher amount of trypsin and amylase activities compared to other treatments. The contents of long‐chain polyunsaturated fatty acids including eicosapentaenoic acid, docosahexaenoic acid and arachidonic acid were significantly higher in the whole body of L. vannamei fed with different levels of C. vulgaris compared to those of control group. After exposure to hypoxia, the survival rate of shrimp fed diets contained different levels of C. vulgaris was higher than that of control group, while no significant differences were observed in ammonia tolerance among treatments. In conclusion, this study indicated that fish meal can be completely replaced with C. vulgaris in the diet of juvenile L. vannamei with no adverse effects on the performance of shrimp.

In this study, juvenile beluga (Huso huso) was fed by the diets containing different carbohydrate to lipid ratios for 5 months. At the end of culture period, proximate compositions of the fish carcasses (moisture, protein, lipid, and ash) were measured. Then, qualitative changes in the fishes were evaluated during 6 months frozen storage (-20 °C) along with recording changes in their Total Volatile Bases Nitrogen (TVN), Thiobarbituric Acid (TBA), Free Fatty Acids (FFA), pH, and muscle texture profile analysis. The results of proximate analysis of the carcasses showed that moisture, protein, and ash of the carcasses increased significantly (p < 0.05) with higher carbohydrate to lipid ratio, but lipid content of the carcasses decreased significantly (p < 0.05). Also, during frozen storage, TVN, TBA, and FFA increased significantly in all the samples (p < 0.05). Significant differences were detected in pH of the treatments (p < 0.05), but these changes didn't follow a regular pattern in all the treatments. The results of muscle texture profile analysis showed lower chewiness, hardness, and gumminess during the first 3 months of frozen storage; however, after 6 month, the values increased significantly compared to those in 3 months. Different characteristics of texture showed significant differences in the treatments during frozen storage (p < 0.05), although these changes didn't follow an identical pattern in all the treatments. It can be concluded that carbohydrate higher than 27% in diet has had adverse effect on quality of fillets during frozen storage. However, lipid levels used in the present study haven't had significant influence on quality of the fillets during the preservation.

In this study, juvenile beluga (Huso huso) were fed diets containing different carbohydrate to lipid ratios for 5 months. At the end of the culture period, proximate compositions of the fish carcasses (moisture, protein, fat, and ash) were measured. Then, qualitative changes in the fishes were evaluated during 24-days refrigeration (4 • C), along with changes in their total volatile bases nitrogen (TVN), thiobarbituric acid (TBA), free fatty acids (FFA), pH, and muscle texture profile analysis. The results of proximate analysis of the carcasses showed that moisture, protein, and ash of the carcasses increased significantly (p < 0.05) with higher carbohydrate to lipid ratio, but fat content of the carcasses decreased significantly (p < 0.05). Further, during refrigeration, TVN, TBA, and FFA increased significantly in all the samples (p < 0.05), but these changes did not follow the same pattern in all the treatments. Tissue hardness decreased during preservation. Although pH changes in the fillets were low, they were significant and without a clear-cut pattern. The results showed that use of different carbohydrate to lipid ratios in diet does not lead to clear-cut changes in qualitative characteristics of beluga fillets during refrigeration.