Abstract:
The availability of high-quality seedlings poses a significant constraint on the development of the aquaculture industry, and the dietary lipid levels are closely related to seedling development. To investigate the effects of dietary lipid levels on the growth, antioxidant capacity, immunity, and stress resistance of zoea larvae from the giant freshwater prawn (
Macrobrachium rosenbergii), this experiment randomly assigned zoea larvae (initial body weight: 0.19±0.05 mg) produced by a single batch of
M. rosenbergii broodstocks into aquaculture tanks. The study was divided into five groups, each comprising six replicates with 5000 larvae per replicate. During the first week, larvae were fed
Artemia nauplii; from the second week onward, they received experimental diets containing crude protein at 52.25% but differing in lipid content-specially at levels of 6%, 8%, 10%, 12%, and 14%. After six weeks of feeding, whole-body samples were conducted to analyze the growth, antioxidant capacity, and immune performance of the larvae. Additionally, 30 post-larval prawns from each parallel were used for air exposure experiments to analyze stress resistance ability. The results showed that when the dietary lipid level exceeded 6%, the survival rate (SR) of the larvae significantly decreased (
P<0.05); the metamorphosis rate peaking in the prawns fed a 10%—12% lipid-level diets, which was significantly higher than that of the other groups (
P<0.05). The final weight, weight gain rate (WGR), and specific growth rate (SGR) first increased and then decreased, reaching a maximum at a lipid level of 12% diet (
P<0.05). The proportions of C18:2n-6 and n-6 HUFA in larvae significantly increased with the elevation of the corresponding fatty acid proportions in the diet. The group with a lipid level of 10%-14% exhibited significantly higher proportions than the group with a lipid level of 6%—8% (
P<0.05). Conversely, the proportion of C20:4n-6 in the larvae significantly increased as the corresponding fatty acid proportion in the diet decreased, with the groups having lipid levels of 8%-14% exhibiting significantly higher proportions than the group with a lipid level of 6%. The proportion of DHA in larvae exhibits a decreasing trend as the proportion of DHA in the diet increases, with a significant reduction observed when the lipid level exceeds 12%. (
P<0.05). The total antioxidant capacity (T-AOC) activity of the larvae was significantly higher at dietary lipid levels of 8%—10% compared to the other groups (
P<0.05). Glutathione peroxidase (GSH-Px) activity peaked at 10% group (
P<0.05). SOD activity was significantly higher at lipid levels of 8%—12% than that in the other groups (
P<0.05), while malondialdehyde (MDA) content was significantly lower at 10%—12% groups (
P<0.05). Dietary lipid levels had no significant effect on acid phosphatase (ACP) activity, but alkaline phosphatase (AKP) activity was significantly higher in larvae fed 10% lipid-level diets compared to the other groups (
P<0.05). Furthermore, in the air exposure experiments, the survival rate of the larvae was significantly higher at a dietary lipid level of 12% compared to the 6%, 8%, and 14% groups (
P<0.05). Therefore, to optimize the growth and health status of
M. rosenbergii zoea larvae in practical production, it is recommended to control the dietary lipid level within 10%—12%.