Influences of replacing dietary fish meal by Antarctic krill meal on growth performance, immunity and muscle quality of white shrimp Litopenaeus vannamei

The present study was conducted to investigate the effects of Antarctic krill Euphausia superba meal replacing dietary fish meal on the growth performance, immunity and muscle quality of white shrimp Litopenaeus vannamei (initial body weight: 4.080 ± 0.143 g, mean±SD). The replacement levels were designed as 0%, 5%, 15%, 30%, 45%, 60%, 75% and 100%, respectively. After a 52-day feeding trial, results showed that the specific growth rate (P = 0.129) and feed intake (P = 0.217) of shrimp were not significantly affected. Feed conversion ratio (FCR, P = 0.000), protein efficiency ratio (PER, P = 0.000) and protein retention (PR, P = 0.000) were significantly affected with a quadratic positive trend for FCR, a linear and quadratic negative trend for PER and a quadratic negative trend for PR. The total haemocyte count (P = 0.307), respiratory burst (P = 0.168), activities of superoxide dismutase (P = 0.221) and glutathione reductase (P = 0.170) in serum were not significantly affected. While, malondialdehyde content (P = 0.000), acid phosphatase (P = 0.000) and alkaline phosphatase activity (P = 0.000) in serum were significantly decreased both in linear and quadratic trend. The carotenoid content in exoskeleton (P = 0.019) and pH in muscle (P = 0.000) were linearly increased. With the increasing replacement levels, n-3 PUFA content (P = 0.001) in muscle significantly decreased and n-6 PUFA (P = 0.000) increased. The ratio of essential amino acid to total amino acid (P = 0.000) and the inosinic acid content in muscle (P = 0.002) were significantly increased with the dietary replacement levels in a linear trend. In conclusion, Antarctic krill meal can totally replace dietary fish meal without negative impact on the growth of L. vannamei. From the perspective of feed utilization, after the quadratic regression analysis of FCR, PER and PR, the appropriate replacement level of dietary fish meal by krill meal for L. vannamei was 52.78%, 68.50% and 47.41%, respectively (i.e., dietary krill meal level was 13.27%, 17.22%, and 11.92%, respectively).