The effects of pre-digested protein sources on the performance of early–mid stage Panulirus ornatus phyllosoma

•Spiny lobster phyllosoma were fed formulated diets containing pre-digested protein sources.•Phyllosoma fed hydrolysed fish meal were significantly larger than all other treatments.•This superior growth is likely attributable to the greater availability of short chain peptides.

Phyllosoma of the tropical spiny rock lobster, Panulirus ornatus, possess a rudimentary digestive system with a limited capacity to digest large protein molecules. As such, to foster the successful aquaculture of this species, research into dietary requirements should place a focus on feed ingredients aligned with digestive capacity. Thus, the aim of the present study was to assess the effects of two protein pre-digestion treatments: acid denaturation and enzyme hydrolysis, on a regular fishmeal ingredient in a novel formulated diet for early–mid stage P. ornatus phyllosoma (Stages III–VIII). Three iso-nitrogenous, iso-lipidic and iso-energetic diets were formulated with 100% of protein originating from intact fishmeal (IFM), acid-denatured fishmeal (DFM) or enzyme hydrolysed fishmeal (HFM) and fed to early–mid stage phyllosoma for a period of 35-days. Growth performance metrics were all significantly higher in phyllosoma receiving the HFM treatment compared to the DFM and IFM treatments. Phyllosoma fed the HFM diet also had the most advanced development stages, with a significantly greater proportion of individuals reaching Stage VII (2). No significant differences were detectable in either the protein-bound or FAA composition of phyllosoma across all treatments, suggesting that the superior growth performance of the HFM fed phyllosoma was the result of an increased abundance of intermediate, shorter chain dietary peptides. The present study suggests that enzyme hydrolysed fishmeal is a superior protein ingredient for artificial diets and most closely resembles the requisite dietary protein format for P. ornatus phyllosoma.