Effects of different water temperature and dietary phosphorus levels on the production performance, tissue and water phosphorus content of Macrobrachium nipponense

Water temperature and dietary phosphorus levels are crucial for the growth of crustaceans. However, the interactions between both factors are still poorly understood in crustacean culture, which brings difficulties in advancing the feed utilization. This experiment was conducted to explore the effects of different temperature and dietary phosphorus levels on the production performance, tissue and water phosphorus content of M. nipponense. Using a 3×3 factorial design, nine groups (respectively named 20/1.1, 20/1.5, 20/1.9, 25/1.1, 25/1.5, 25/1.9, 30/1.1, 30/1.5, 30/1.9) were formed, including three water temperature (20, 25 and 30 °C) and three dietary phosphorus levels (1.1%, 1.5% and 1.9%). Each diet was tested by 4 replicates. Prawns were reared in the indoor circulation systems for 8 weeks. The results showed that, in terms of water temperature, the final body weight (FBW), specific growth rate (SGR) and weight gain rate (WGR) of the 30 °C group were all significantly higher than those of the 20 °C, but showed no statistical difference with those of the 25 °C. However, the opposite was true for feed intake and feed conversion rate (FCR). In addition, the phosphorus retention efficiency (PRE) and hemolymph phosphorus levels of the 30 °C group were both significantly higher than those of the other two groups, meanwhile the hemolymph phosphorus level of this group was significantly higher than that of the 25 °C group, but showed no significant difference with the 20 °C group. In terms of dietary phosphorus levels, the FBW, WGR, PRE and hemolymph calcium level of the 1.9% phosphorus level group were all significantly lower than those of the other groups, while phosphorus intake and FCR showed the opposite trend. The SGR of the 1.9%phosphorus level group was significantly lower than that of the 1.5% group, but showed no statistical difference with that of the 1.1% group. Besides, the whole-body phosphorus contents of the 1.1% group was significantly lower than that of the other groups, and the hemolymph calcium content of this group was significantly higher than that of the 1.9% group, but there was no significant difference with the 1.5% group. Serum alkaline phosphatase (AKP) activities of the 1.5% group was significantly higher than that of the 1.1% group, but showed no statistical difference with those of the1.9% group. Furthermore, feed intake, phosphorus intake, PRE, hemolymph phosphorus level and AKP activities were all significantly affected by the interaction between water temperature and dietary phosphorus level with the maximized values observed in the 20/1.1, 25/1.9 and 30/1.9, 30/1.1, 30/1.9, 25/1.5 group, respectively. Additionally, water phosphorus levels increased significantly with increasing sampling time, while the water phosphorus level of the 20/1.5 group was significantly higher than those of the 25/1.1 and 30/1.1 groups. Overall, M. nipponense in the 30/1.1 group obtained the best growth performance and feed efficiency coupled with low phosphorus emission.