Chromium polynicotinate inclusion in the diet affects growth, feed utilization, and chromium retention in Japanese seabass Lateolabrax japonicas fed a low protein starch-based diet

Abstract

Chromium (Cr) has been reported to enhance carbohydrate utilization in animals. This study investigated the effects of supplementation with dietary chromium polynicotinate (Cr-Nic) on the growth, tissue chromium retention, and feed utilization in juvenile Japanese seabass Lateolabrax japonicus. Six diets containing 42% crude protein (CP) were supplemented with 0 (42%CP-control), 5, 10, 20, 40, or 80 mg Cr-Nic kg−1 diet; another diet containing 45% crude protein with no Cr-Nic supplementation (45%CP-control) was also formulated to test whether the dietary protein level can be lowered through Cr-Nic supplementation. Wheat starch was used as the carbohydrate source for all diets. Each diet was fed for 10 weeks to triplicate groups of seabass with an initial body weight of 9.35 ± 0.79 g. Fish fed diets supplemented with 5 and 10 mg kg−1 Cr-Nic had a significantly greater specific growth rate (SGR) compared with fish fed all other diets other than those fed a diet with 20 mg kg−1 Cr-Nic. Fish fed 5 or 10 mg Cr-Nic kg−1 diets had a significantly higher feed efficiency (FE) and protein efficiency ratio, but significantly lower feed intake compared with fish fed a 42%CP-control diet. Tissue Cr concentrations were significantly and positively correlated, whereas Cr-Nic retention efficiency was negatively correlated, with dietary Cr-Nic supplementation. Analysis of SGR and FE by second-order regression indicated that the optimal level of Cr-Nic supplementation for L. japonicas was 6.4–9.5 mg kg−1 diet. Thus, dietary supplementation with Cr-Nic enabled a reduction in dietary protein content of at least 3% without negatively impacting seabass growth.