Bioavailability of arginine from Indian mustard protein concentrate and meal compared with that of a soy protein concentrate in rainbow trout (Oncorhynchys mykiss)

Relative bioavailability (RBV) of arginine (Arg) from Indian mustard protein concentrate (IMC, 62% crude protein) and Indian mustard meal (IMM, 42% crude protein), and a commercially available soy protein concentrate (SPC, 57% crude protein) was compared with that of crystalline L‐arginine (L‐Arg) in rainbow trout. A basal diet highly deficient in Arg (1.23%) was formulated. Eight other isoproteic and isoenergetic diets were formulated to contain ~1.35% and ~1.5% Arg by adding increasing amount of IMC, IMM, SPC and L‐Arg. The experimental diets were fed for 16 weeks using a standard protocol. Growth rate, weight gain (g fish^?1) and protein (PD, g fish^?1) and lipid (LD, g fish^?1) deposition were increased linearly with increasing level of Arg from all ingredients. Arg availability from protein‐bound sources were equal or higher than those from L‐Arg. RBV of Arg from IMC, IMM and SPC were ranged from 100% and 123% than that from L‐Arg (assumed as 100% bio‐available). Among the ingredients, only the RBV of Arg from IMC was significantly higher than those from SPC (P < 0.05). The findings suggest that the RBV of Arg from IMC and IMM are very good and comparable to that of the commercial SPC used in this study.