Dietary protein requirements of kuruma shrimp Marsupenaeus japonicas in recirculating aquaculture system

The farming of Marsupenaeus japonicas in recirculating aquaculture system (RAS) is relatively recent; consequently, knowledge of their dietary protein requirements is still insufficient. Due to the specific ecological conditions of RAS, these systems may affect the nutritional requirements of shrimp. Therefore, this study aimed at assessing the optimal protein requirement of M. japonicas in RAS. Six experimental diets were devised to contain 35%, 40%, 45%, 50%, 55%, and 60% crude protein (P35, P40, P45, P50, P55, and P60, respectively) and were fed in triplicate groups of 20 shrimp (initial body weight 1.86 ± 0.01 g) at a feeding rate of 3.0% body weight per day for 56 days. At the end of the feeding period, the optimal protein requirement was estimated at 46.13% for weight gain rate, and specific growth rate with all groups exhibited high survival rates. The P45 diet increased the digestive enzyme activities, antioxidant indices, and improved intestinal morphology, while the P50 diet showed the highest intestinal microbiome diversity. The experimental results showed that diets containing higher protein seemed to have compromised the antioxidant status of shrimp and did not necessarily result in better growth. Hence, results from this study suggested that the optimal protein requirement of M. japonicas fed in RAS was determined to be 46.13%, but protein levels up to 50% can be beneficial to the intestinal microbiome diversity.