a Met requirements of channel catfish (NRC, 2011). b All diets were supplemented with 0.2 mg g−1 Stay-C© 35 (DSM Nutritional
Products, Basel, Switzerland), which provided an active vitamin C level ≥50 mg kg−1
in finished diets. c Sprayed on finished diets. d Digestible energy in kilojoules per gram of dietary protein. e Based on 90% dry matter. f Nitrogen-free extract (NFE) was calculated by difference.
g Lutein and zeaxanthin.