Identification of target muscle-proteins using Western blotting and high-resolution mass spectrometry as early quality indicators of nutrient supply practices in rainbow trout (Oncorhynchus mykiss)

Using Western blotting and mass spectrometry we investigated the changes in trout muscle proteins as affected by pre-slaughter nutrient supply practices, including starvation and feed restriction, in comparison to full feeding. A number of fillet quality attributes were also analyzed. During cold storage, fillet firmness was not influenced by the feeding practices, while the initial pH was higher in the treated trout. The early appearance of an alpha-actin 26 kDa-fragment and the detection of enigma protein were both signs of impaired muscle integrity, observed only in the restricted conditions, where water holding capacity was initially lower. The detection of reticulon involved in authophagy and the early finding of apolipoprotein A-I-1 fragments in these restricted samples was consistent with their early degradation in comparison to full ration controls. Since specific protein changes reflected differences in feed management, the use of selected muscle proteins as sensitive indicators of fillet quality is proposed.