The evaluation of dietary substitution of fishmeal with marine microalgae Arthrospira platensis meal on growth parameters, nutrient digestibility, immunity and stress of narrow clawed crayfish (Pontastacus leptodactylus)

Abstract

Introduction: This study aimed to evaluate the effect of the dietary substitution of Arthrospira platensis meal on growth, immunity, nutrient digestibility and stress tolerance of narrow clawed crayfish, Pontastacus leptodactylus. Materials & methods: Different levels of Arthrospira microalgae meal were 0, 25, 50, 75 and 100%. Narrow clawed crayfish with an average initial weight of 4.24±0.09 g were selected in a completely randomized design with three replications for 63 days. Results: The obtained results showed that higher juvenile final weights (24.35 g) were observed by 75% fishmeal substitution with Arthrospira meal. Moreover, specific growth rate (2.78% day-1), and protein efficiency ratio (3.24) had higher values in 75% fishmeal substitution with Arthrospira diet compared to the control (p<0.05). In contrast, feed conversion ratio (1.91) was lowest in animals fed on diets containing 75% Arthrospira meal replacement with fishmeal (p<0.05). Productive protein value (59%), in vivo apparent digestibility coefficients of organic matter (83.17%), and in vivo apparent digestibility coefficients of crude protein (92%) significantly increased compared to the control (p<0.05). Phenoloxidase, superoxide dismutase, nitric oxide synthase, and lysozyme, as well as amylase, lipase, and alkaline protease activities were improved with an increase in the dietary inclusion level of Arthrospira meal. Besides, Lactobacillus count and Escherichia coli count showed increasing and decreasing trends during the increase in the level of fishmeal replacement, respectively (p<0.05). Finally, two-slope straight broken line regression models estimated that the appropriate level of substitution of fishmeal (%) with Arthrospira meal to reach the highest specific growth rate and weight gain, and the best feed conversion ratio could be 76.84%, 80.24%, and 88.91%, respectively. Conclusion: In conclusion, the results showed the fishmeal replacement with A. platensis meal in the range of 76-89% as a reliable protein alternative in the aquafeed industry.