Nitrogen and phosphorus budgets of the bullfrog (Aquarana catesbeiana) in different body weights

Abstract

Aquaculture water eutrophication is primarily driven by nitrogen (N) and phosphorus (P), partly derived from animal excretions. Understanding the N and P metabolism is crucial for mitigating environmental pollution caused by aquaculture. This study investigated N and P budgets in bullfrogs (Aquarana catesbeiana) of varying body weights: 52.63 ± 0.33 (50 g), 98.64 ± 0.55 (100 g), 159.97 ± 0.58 (150 g) and 250.01 ± 2.61 (250 g). Our findings highlighted the significant influence of body size on N and P budgets in bullfrogs. As body weight increased, feed intake rate, N and P intake rates, growth rate, N and P growth rates, N and P metabolism rates, feces rate, while the N and P feces rates all decreased. The relationship between each index and body weight was expressed as a power function (Y = aWb). The N and P budget equations for bullfrogs were established as follows: 100 Intake N (IN) = 30.75 Growth N (GN) + 62.48 Metabolism N (MN) + 2.10 Feces N (FN) + 4.67 Others (ON), and 100 P Intake P (IP) = 74.16 Growth P (GP) + 4.18 Metabolism P (MP) + 7.92 Feces P (FP) + 13.75 Others (OP). In conclusion, daily feeding per body weight of bullfrog should be reduced as their body weight increased. Consequently, the dietary protein should be progressively lowered to minimize nitrogen waste, while bullfrogs demonstrated effective utilization of P in the soybean meal diet.