Dietary phosphorus requirement of bullfrog Aquaranacatesbeiana

Abstract

This experiment investigated the dietary phosphorus (P) requirement of bullfrogs Aquaranacatesbeiana. Six diets containing available P (AP) levels of 0.29% (the control group), 0.47%, 0.65%, 0.88%, 1.06% and 1.24% were formulated and fed to bullfrogs for 56 days. As dietary AP level increased from 0.29% to 1.24%, weight gain rate increased and then decreased, reaching the highest at the AP level of 0.88% (P < 0.05). Compared to the control group, content of crude protein in the whole-body was significantly increased in bullfrogs fed the 0.88% AP diet (P < 0.05). Content of crude lipid in the whole-body was significantly decreased in bullfrogs fed the 0.65%, 0.88%, 1.06% and 1.24% AP diets compared to those fed the 0.29% and 0.47% AP diets (P < 0.05). Bullfrogs fed the 0.65%, 0.88%, 1.06%, and 1.24% AP diets had higher content of serum P than those fed the 0.29% and 0.47% AP diets (P < 0.05). Activity of glutamic pyruvic transaminase in the serum was significantly decreased in bullfrogs fed the 0.88%, 1.06% and 1.24% AP diets compared to those fed the 0.29% and 0.47% AP diets (P < 0.05). Bullfrogs fed the 0.65%, 0.88%, 1.06% and 1.24% AP diets had lower contents of total cholesterol in the liver and triglycerides in the serum than the control group (P < 0.05). Meanwhile, bullfrogs fed the 0.47%, 0.65%, 0.88% and 1.06% AP diets had higher total antioxidant capacity in the serum than the control group (P < 0.05). Compared to the control group, contents of P and calcium in the whole-body were significantly increased in bullfrogs fed the 0.65%, 0.88%, 1.06% and 1.24% AP diets (P < 0.05). Compared to the control group, bullfrogs fed the 0.88%, 1.06% and 1.24% AP diets had lower expression of sodium-dependent phosphate transporter in the intestine and kidney, and higher expression of hormone-sensitive triglyceride lipase in the liver (P < 0.05). Bullfrogs fed the 0.88% and 1.06% AP diets had higher the mucosal fold height than those fed the 0.29% and 1.24% AP diets (P < 0.05). Compared to those fed the 0.29% and 1.24% AP diets, the abundance of potentially pathogenic bacteria Serratia and Acinetobacter in the intestine was decreased in bullfrogs fed the 0.88% AP diet. Using the weight gain rate, feed efficiency, whole-body and serum P content as evaluation indicators, the AP requirements of bullfrogs was 0.82% to 0.89%.