Growth, serum biochemical parameters, salinity tolerance and antioxidant enzyme activity of rainbow trout ( Oncorhynchus mykiss ) in response to dietary taurine levels.

This study evaluated the effect of dietary taurine levels on growth, serum biochemical parameters, salinity adaptability, and antioxidant activity of rainbow trout ( Oncorhynchus mykiss ). Four diets were formulated with taurine supplements at 0, 0.5, 1, and 2% w/v (abbreviated as T ₀ , T _0.5 , T ₁ , and T ₂ , respectively). Rainbow trouts (initial weight of 80.09 ± 4.72 g) were stocked in tanks (180 L capacity), and were fed these diets for six weeks and subsequently underwent salinity acclimation. Physiological indicators were determined before salinity acclimation at 1, 4, 7, and 14 days afterwards. Results showed that there were no significant differences in growth performance (final mean weight ranged from 182.35 g to 198.48 g; percent weight gain was between 127.68% and 147.92%) of rainbow trout in freshwater stage, but dietary taurine supplement significantly increased serum-free taurine content. After entering seawater, the Na ⁺ -K ⁺ -ATPase activity of T ₂ group returned to its freshwater levels, and the serum cortisol content was significantly higher than T ₀ and T _0.5 groups. At the end of this experiment, the liver superoxide dismutase activity in the T ₀ and T _0.5 groups was significantly lower than in the T ₁ and T ₂ groups, and the liver catalase in the T ₀ group was the lowest whereas that in the T ₂ group was the highest. Muscle malondialdehyde content was the highest in the T ₀ group, and the lowest in the T ₂ group. Based on the results of this study, supplement of dietary taurine (0.5-2%) enhanced the salinity tolerance in rainbow trout, which increased with the higher taurine concentration.
Competing Interests: Conflicts of interestThe authors declare that there is no conflict of interest.
(© Ocean University of China 2021.)