Each year ~16M tonnes of wild caught fish are converted into 5M tonnes of fishmeal (FM); a quantity which has been relatively constant for the past decade. Approximately 70% of this FM is used in aquafeeds. The global aquaculture industry is rapidly expanding and in 2020 production of finfish reached 55.5 M tonnes, doubled since 2010. If aquaculture is to maintain this growth in the face of a stable supply of FM, more sustainable protein ingredients must be identified to enable the expansion of the industry.
Our recent studies have investigated the use of novel alternative proteins in diets for marine yellowtail kingfish (YTK) (Seriola lalandi) and barramundi (Lates calcarifer). The proteins trialled have included black soldier fly (BSF, Hermetia illucens) larvae meal and single cell proteins (SCP) derived from Methylococcus capsulatus (StringBio Pty. Ltd.) and Cupriavidus necator (Kiverdi Inc.) as replacements for FM. The studies conducted in YTK have found digestibility and FCR of BSF and Methylococcus capsulatus proteins were equal to or better than control FM diets. However, YTK showed reduced feed intake when FM was replaced at high inclusion levels with these proteins. Improved palatability would be highly beneficial in achieving FM-free diets for YTK.
Barramundi do not appear to have the same palatability issues as YTK, and this species demonstrates the path forward for a zero FM diet. A 56-day study investigated the effects of gradual replacement of FM with SCP derived from either Methylococcus capsulatus (MC) or Cupriavidus necator (CN) on the growth performance, feed utilization and fish health in barramundi. The treatment diets included a control containing 15% FM and three diets for each SCP at inclusions of 10%, 20% and 30% (corresponding to 33%, 66 and 100% FM replacement). The feed consumption across all treatments was uniform with no effect of either SCP or inclusion level. Weight gain increased significantly in barramundi fed the diets containing CN at 30% inclusion compared to the control diet (P > 0.05). The improved growth in barramundi fed CN at 30% resulted from an improved FCR compared to the control diet (Table 1).