Effects of dietary fishmeal replacement with Spirulina platensis on the growth, feed utilization, digestion and physiological parameters in juvenile gibel carp (Carassis auratus gibelio var. CAS III)

A 60-day growth experiment was conducted to investigate the effect of dietary replacement of fishmeal by Spirulina platensis on growth performance, digestion and physiological parameters in juvenile gibel carp (5.0 +/- 1.0g). Four diets were formulated to replace 0 (SP0), 50% (SP50), 75% (SP75) and 100% (SP100) of dietary fishmeal protein by S.platensis respectively. Other two diets based on SP100 were supplemented with 2% dicalcium phosphate (SP100+P) or 0.28% coated lysine (SP100+Lys). The results showed that no significant differences of specific growth rate (SGR), feed efficiency (FE), feeding rate (FR) and protein efficiency ratio (PER) were observed between SP0 group and the replacement groups (SP50, SP75 and SP100). FE and PER of fish-fed SP100+Lys diet were significantly higher than the fish-fed SP100 diet (p<.05). Apparent digestibility coefficients (ADCs) of dry matter, protein, energy and phosphorus increased significantly with the increasing S.platensis inclusion. Meanwhile, fish from SP100+P or SP100+Lys group had higher ADCs of nutrients compared to the SP100 group (p<.05). Compared with SP0 diet, fish-fed S.platensis diets had higher activities of plasma superoxide dismutase, hepatopancreas total antioxidant capacity, plasma alkaline phosphatase and plasma lysozyme, as well as the lower content of plasma malondialdehyde. The present results indicated that dietary fishmeal could be fully replaced by S.platensis without any negative effects on growth performance of gibel carp. Supplementation of lysine in the S.platensis replacement diet could further improve the feed utilization of gibel carp