Pyridoxine (B6 ) is a water-soluble vitamin and involved in amino acid metabolism. Since pyridoxine acts as a coenzyme in protein metabolism, its dietary requirement varies depending on the dietary protein levels . This study was conducted to verify the interacting effects of dietary protein and pyridoxine levels on the growth, innate immunity, antioxidant capacity and digestive enzyme activity of Pacific white shrimp.
Pyridoxine was supplemented at 0, 40, 80 and 120 mg/kg in a low protein (LP, 31.7% ) and a high protein (HP, 42.6%) diets (designated as LP0, LP40, LP80, LP120, HP0, HP40, HP80 and HP120, respectively) . Total 408 shrimp ( 6.44 ± 0.03 g) were distributed in 24 tanks (240 L). T hree replicate groups of shrimp were fed one of the diets six times daily for 42 days.
In LP group, the growth performance (final body weight, weight gain and specific growth rate ) was significantly higher in the pyridoxine– supplemented groups than in LP0 group . In HP group, there was no significant difference in the growth performance among all groups. T rypsin activity was significantly improved in the pyridoxine–supplemented groups ( except for LP40 ) compared to that in LP0 and HP0 groups. C hymotrypsin activity was not significantly different in LP and HP groups. Lipase activity was significantly improved in pyridoxin–supplemented groups regardless of protein levels . LP120 group showed significantly higher antioxidant capacity ( glutathione peroxidase, catalase and total antioxidant capacity) than LP0 group . C atalase activity was significantly higher in LP80 group than in LP0 group. In the HP groups, pyridoxine–supplemented groups showed significantly higher antioxidant capacity than HP0 group.
The optimum dietary pyridoxine level in LP diet and HP diet was established to 115.5 mg/kg and 59.4 mg/kg, respectively. Dietary pyridoxine requirement for the shrimp seems related to the dietary protein levels. The results on innate immunity and gene expressions will be further discussed in details. Our results suggest optimal levels of pyridoxine for different dietary protein levels, leading to improved growth, health and cost-effective feeding of Pacific white shrimp.