Vitamin K₃, as either menadione nicotinamide bisulfite [MNB] or menadione sodium bisulphite [MSB], is safe for all animal species and authorized for use as a nutritional additive without time limit or maximum content under Council Directive 70/524/EEC. However, both MSB and MNB are sensitive to light and heat and considerable loss can occur in feed manufacture. The inclusion of MNB or MSB in fish diets in a way where their viability and stability is optimized will facilitate greater opportunity for uptake into fish tissue. Studies have shown that MSB may be toxic in mammals and one study found that Atlantic salmon fed MSB (at a concentration of 30 mg/kg) showed reduced performance. In contrast, MNB has been shown to be relatively well tolerated at high concentrations in rainbow trout. As a result of these studies, MNB is the more commonly used form of vitamin K₃ added to fish feeds and will be used in this trial.

Thus, OKIN aims to examine the effect of fortifying salmon diets with different levels of vitamin K₃ on the concentration of vitamin K in the resulting fillet and identification of the optimized level of inclusion in the diet.