Dietary protein requirement of juvenile giant salamander (Andrias davidianus)

In order to determine the dietary protein requirement of juvenile giant salamander, 6 isolipidic diets were formulated to contain graded levels of D1(43.7%), D2(47.1%), D3(51.3%), D4(55.7%), D5(59.9%) and D6(64.4%) crude protein(dry matter) to feed juvenile giant salamander with initial weight (20.99±0.15)g for 92 days. The results show that: ① Dietary protein levels had significant effects on weight gain rate of giant salamander, and it reached the highest in the D4 group, which is 276.4% higher than group D1, and the whole body protein deposition rate and muscle RNA, RNA/DNA ratio, pepsin, H⁺-K⁺- ATPase in stomach, trypsin, lipase and Na⁺-K⁺- ATPase in intestine, liver superoxide dismutase (SOD) reached the best in the group D4, and the malondialdehyde (MDA) in liver and intestine were both the lowest in group D4. ② The content of muscle crude protein increased linearly with the increase of dietary protein level, while the fat content in giant salamanders declined linearly, and there was no significant difference in moisture and crude ash of whole body between different groups, and whole body crude protein increased first and then tended to be stable, reached the highest in the group D4. ③ The skin collagen content in group D4 reached the highest, increasing by 27.8% compared with D1. With weight gain rate, muscle RNA/DNA ratio, protein deposition rate, and skin collagen content as evaluation indexes, the optimum dietary protein level of the giant salamander was 55.9%-58.3%(based on dry mater), and this dietary protein level can significantly improve gastric acid secretion, the digestion and absorption, and antioxidant capacity, and increase the nutrient deposition, thus promote growth and feed conversion; While low protein level diet significantly inhibited the growth of A. davidianus.