Dietary ß-Hydroxy-ß-Methylbutyrate Supplementation Affects Growth Performance, Digestion, TOR Pathway, and Muscle Quality in Kuruma Shrimp (Marsupenaeus japonicas) Fed a Low Protein Diet.

An 8-week feeding trial was performed to evaluate the effects of dietary ß-hydroxy-ß-methylbutyrate (HMB) supplementation on growth performance and muscle quality of kuruma shrimp (Marsupenaeus japonicas) (initial weight: 2.00 ± 0.01 g) fed a low protein diet. The positive control diet (HP) with 490 g/kg protein and negative control diet (LP) with 440 g/kg protein were formulated. Based on the LP, 0.25, 0.5, 1, 2 and 4 g/kg ß-hydroxy-ß-methylbutyrate calcium were supplemented to design the other five diets named as HMB0.25, HMB0.5, HMB1, HMB2 and HMB4, respectively. Results showed that compared with the shrimp fed LP, the HP, HMB1 and HMB2 groups had significantly higher weight gain and specific growth rate, while significantly lower feed conversion ratio (p < 0.05). Meanwhile, intestinal trypsin activity was significantly elevated in the above three groups than that of the LP group. Higher dietary protein level and HMB inclusion upregulated the expressions of target of rapamycin, ribosomal protein S6 kinase, phosphatidylinositol 3-kinase, and serine/threonine-protein kinase in shrimp muscle, accompanied by the increases in most muscle free amino acids contents. Supplementation of 2 g/kg HMB in a low protein diet improved muscle hardness and water holding capacity of shrimp. Total collagen content in shrimp muscle increased with increasing dietary HMB inclusion. Additionally, dietary inclusion of 2 g/kg HMB significantly elevated myofiber density and sarcomere length, while reduced myofiber diameter. In conclusion, supplementation of 1-2 g/kg HMB in a low protein diet improved the growth performance and muscle quality of kuruma shrimp, which may be ascribed to the increased trypsin activity and activated TOR pathway, as well as elevated muscle collagen content and changed myofiber morphology caused by dietary HMB.

Impacts of replacement of dietary fish oil by vegetable oils on growth performance, anti-oxidative capacity, and inflammatory response in large yellow croaker Larimichthys crocea.

A 12-week feeding trial was conducted to evaluate the effects of replacement of dietary fish oil by palm and linseed oils on the growth performance, anti-oxidative capacity, and inflammatory responses of large yellow croaker (initial body weight: 36.82 ± 0.29 g). The control diet was designed to contain 6.5% of fish oil, and named as FO. On the basis of the control diet, the fish oil was 100% replaced by palm and linseed oils, and these two diets were named as PO and LO, respectively. Results showed that the specific growth rate significantly reduced in the PO and LO groups. Crude lipid content in liver of fish fed FO was significantly lower than that in the PO and LO groups. Fatty acid composition in liver reflected the dietary input. Compared with the FO group, palm oil inclusion significantly decreased expressions of superoxide dismutase 1, catalase, and nuclear factor erythroid 2-related factor 2 in liver, while linseed oil inclusion significantly increased expressions of above genes. However, both of the PO and LO groups had a significantly lower total anti-oxidative capacity in liver than the fish fed FO. Dietary palm and linseed oils significantly decreased expressions of arginase I and interleukin 10, and increased expressions of tumor necrosis factor α, interleukin 1ß, toll-like receptor 22, and myeloid differentiation factor 88 in liver. In conclusion, total replacement of dietary fish oil by palm and linseed oils could suppress growth performance and liver anti-oxidative capacity, and induce inflammatory responses of large yellow croaker.