4. Discussion
In the present study, crude fiber has been applied as a marker for
monitoring digestibility of fat and protein in salmon feed in use at commercial
salmon farms along the coast of Norway. Mean apparent fat and
protein digestibility was high, indicating that both protein and fat were
readily digested and available for growth, and there was a trend for increased
fat digestibility over the study period. Factors related to feed
and environment influenced digestibility significantly. Based on the
apparent digestibility of fat and protein, the DE and DP of the feed
were realized and compared to the optimized DE and DP given by the
feed producers. DP was overall marginally (−0.28 units) below optimized
values, while DE was 0.58 MJ/kg below with significant differences
between feed companies.