Advances in the proof of concept of feed restriction as a strategy to improve Arctic charr cultivation: insights on the role of dietary nucleotides and digestive plasticity in supporting growth

The natural predispositions of Arctic charr ( Salvelinus alpinus (Linnaeus, 1758)), a species associated to the Holarctic realm, to sustain and recover from extended periods of feed restriction and growth depression during the winter were cautiously explored in an aquaculture context. The degree to which a growth recovery is achieved upon refeeding is governed by the timing and the intensity of the restriction and the coping mechanisms occurring under the rearing conditions provided. Advantages for aquaculture are reduced labor, feed, and phosphorus load. We investigated the effect of (1) a pilot-scale cyclical restriction-refeeding sequence over three size classes (Pre-experiment) and (2) the inclusion of dietary nucleotides during recovery on growth and feeding metrics, and sustainable profitability value (Experiment). Despite a feed reduction of ∼30%, no clear effects on growth were observed, translating in savings of 1.84 CAD per kg of produced fish. Incorporation of dietary nucleotides during the recovery phase resulted in improved growth and feed conversion efficiency and created an upward shift of digestive organs allometries. Nucleotides exclusion after 60 days subsided all the above. Overall, feed restriction induced net positive outcomes that increased the sustainable profitability value of the feeding strategy. We suggest that severe restriction leading to low adiposity and nucleotide supplementation are required for the full expression of compensatory growth in Arctic charr.