The influence of the ratio of protein energy to total energy in the feed on the activity of protein synthesis in vitro, the level of ribosomal RNA and the RNA-DNA ratio in white trunk muscle of Atlantic cod (Gadus morhua)

1. 1. Cod ( Gadus morhua ) were fed diets containing protein energy to total energy levels (PE/TE) of 10.0, 20.6, 29.6, 38.4, 56.2 and 74.1% for 21 days. 2. 2. Ribosomes were isolated from the white trunk muscle tissue, the capacity for protein synthesis in vitro determined and related to muscle tissue wet weight, rRNA and DNA. 3. 3. Protein concentrations of less than 47.4% PE/TE in the diets reduce the ribosomal capacity for protein synthesis per g wet weight and per mg DNA, and the tissue contents of rRNA and ratio of rRNA/DNA. 4. 4. The capacity for muscle protein synthesis in vitro is a significant and sensitive parameter of protein inadequacy in fish diets.