From waste to feed: the Black Soldier fly (Hermetia illucens) as a novel feed source for monosex tilapia (Oreochromis niloticus)

Abstract

The aquafeed industry is highly dependent on fishmeal (FM) and high-protein plant substitutes. Rising costs and sustainability concerns are fueling the search for novel alternatives. Black Soldier Fly (BSF) larvae (Hermetia illucens) have been demonstrated to be a potential new source of sustainable protein. While they can be grown on a wide range of waste-substrates, have a short life-cycle, and a favourable nutritional profile, they can be seen as a credible candidate. In this thesis, we focused on the selection of a potential substrate in a local context, and the type of larval stage to harvest in order to optimise both production and quality of the maggot meal (MM). From these preliminary studies fruit waste were selected to grow the larvae, harvested at the “white larvae” stage to produce the MM. As the availability of MM is yet –far- from being sufficient to cover the ever-growing demand for aquafeed, a strategic use was decided in contextualised and commercially-relevant researches. In large-scale tilapia farm, all-male production is desired to optimise the production as they grow bigger and faster than females. To do so 17α-methyltestosterone is added to the feed during the first 21 days of the fry. To maximize the ingestion, low quantities but high quality feed are required. In this context, the MM was used as a feed-hormone carrier for tilapia fry (Oreochromis niloticus) in two experiments. Whereby the first was based on simple substitution of fish meal (FM) and commercial feed with MM (Chapter 5), the second compared 12 isoenergetic and isoproteic formulated feeds based on a prior MM digestibility analysis (Chapter 6). Results indicated that different dietary inclusions of MM did not significantly affect sex reversal rates nor fish production performance, suggesting that MM offers potential as a locally sourced feed ingredient for tilapia hatchery. This strategic application is further enhanced by the potential to co-located MM and fry-production offering producers’ greater ability to manage quality assurance.