Pre-hydrolysis improves utilisation of dietary protein in the larval teleost Atlantic halibut (Hippoglossus hippoglossus L.)

Larval age and size did not influence the absorption and utilisation of the hydrolysed protein preparations. This was different from the intact protein, as significantly higher fractions of the intact protein were absorbed by the larvae at 31 days past first feeding (dpff) than by larvae at 25 dpff. Analysis of the faecal evacuation suggested that the poor protein utilisation in the younger larvae was due to enhanced faecal evacuation, which in some larvae was more than 50% only 4 h post diet administration, at a time when the process of digestion and absorption was far from complete. This indicated that faecal evacuation is a critical factor in the utilisation of slowly digested and absorbed feed components, such as intact proteins, by fish larvae.