Myosin heavy chain mRNA expression correlates higher with muscle protein accretion than growth in Atlantic salmon, Salmo salar

In order to link growth and protein accretion in Atlantic salmon the mRNA expression of muscle myosin heavy chain (MyHC) was analysed. MyHC gene is expressed throughout muscle development and is consistent with the hypertropic growth in fish. Total RNA was isolated from white muscle tissues (N = 32) from salmon fed a fish meal based diet with three levels of solubilised protein incorporated as fish protein hydrolysate (FPH) control (0 g kg− 1), medium (180 g kg− 1) and high (300 g kg− 1) FPH inclusion. The salmon were PIT-tagged and fed the experimental diets for a period of 68 days. A high level of dietary FPH resulted in significant up-regulation of MyHC by a factor of 2.4 compared to fish fed the medium FPH inclusion. The fish with highest MyHC expression also contained significant higher levels of muscle protein. MyHC expression correlated higher with protein accretion than individual specific growth rate (SGR) in salmon. These observations indicate that MyHC mRNA expression can be a useful marker for understanding of growth and protein accretion in Atlantic salmon.