Dietary supplementation of Chlorella vulgaris improved growth performance, immunity, intestinal microbiota and stress resistance of juvenile narrow clawed crayfish, Pontastacus leptodactylus Eschscholtz, 1823

A 63- day feeding trial was conducted to study the effect of fishmeal substitution levels with Chlorella vulgaris meal (25, 50, 75 and 100%) on the growth performance, nutrient digestibility, immune responses and the stress resistance of juvenile narrow clawed crayfish, Pontastacus leptodactylus (6.19 +/- 0.13 g). The highest values of final weight (25.52 g), specific growth rate (2.24% body weight day(-1)), protein efficiency ratio (3.24), the protein productive value (54.67%), in vivo ADC(OM) (88.40%) and in vivo ADC(CP) (93.50%) and the lowest feed conversion ratio (1.49) were observed in the juvenile crayfish fed the diet containing 75% fishmeal substituted level with chlorella meal (p < 0.05). With an increment in the dietary inclusion level of chlorella meal, the activities of alkaline protease (r(2) = 0.97), lipase (r(2) = 0.98), amylase (r(2) = 0.97), phenoloxidase (r(2) = 0.98), superoxide dismutase (r(2) = 0.99), lysozyme (r(2) = 0.96) and nitric oxide synthase (r(2) = 0.98) were promoted as a third-order polynomial regression model (p < 0.05). There was an increasing trend in Lactobacillus count (r(2) = 0.99) and a decreasing trend in Escherichia coli count (r(2) = 0.97) with an increase in the fishmeal substitution level with chlorella meal. Based on the broken line regression model, the dietary fishmeal substitution level (%) with chlorella meal for maximum growth (SGR) and weight gain values and minimum FCR value of crayfish were estimated to be 85.49%, 78.14% and 78.13%, respectively.

Automated summary

This study investigated the effects of fishmeal substitution with Chlorella vulgaris meal on the growth performance, immune response, and stress resistance of juvenile narrow clawed crayfish. The results showed that a diet containing 75% fishmeal substitution with chlorella meal resulted in the highest growth performance and improved immune response. There was also a positive correlation between the dietary inclusion of chlorella and the activities of digestive enzymes and immune-related enzymes.