By supplying nutrients in far greater amounts than natural ecosystems do, formulated feeds allow farmed fish to grow rapidly. The conversion of absorbed dietary proteins into muscle fibres is the main driver of fish growth. However, fish also utilise dietary proteins as a source of energy, which results in the release of nitrogen in the form of ammonia. Ammonia accumulation may compromise natural water bodies equilibriums (e.g. eutrophication). Thus, efficient conversion of dietary nutrients into fish growth is key to the sustainability of farmed fish production (aquaculture).
The freshwater Nile tilapia is the third most farmed fish species worldwide. In this thesis, we tested if the protein and energy content of tilapia feeds can be optimised to maximise growth and feed conversion efficiency. Moreover, we tested if contrasts in muscle fibre recruitment induced during early life affect the growth capacity and dietary protein-to-energy dietary requirements of Nile tilapia later in life.
We found that as far as protein utilisation efficiency and growth are concerned, there is no single optimal dietary P:E for Nile tilapia. Moreover, our results indicate that white muscle fibre recruitment persists in Nile tilapia as heavy as 700 grams, while its rate does not affect fish protein gain capacity.