Ingestion, assimilation and utilization of raw Spirulina by larval tilapia Oreochromis niloticus during larval development

Ingestion, assimilation and utilization of raw Spirulina by larval tilapia of varying sizes were examined to elucidate the effect of Spirulina on larval tilapia at different growing stages during the development. High initial concentration of 14C-labeled Spirulina was offered to larval tilapia from the onset of exogenous feeding to 3.8 cm SL to ensure ad lib feeding during 1 h feeding period. Ingestion efficiency (IE, %), assimilation efficiency (AE, %), utilization efficiency (UE, %), and metabolism efficiency (ME, %) were investigated by monitoring the fate of labeled food. IE increased with the development of larvae. Larval tilapia could ingest 2.6% to 90.0% of the available Spirulina biomass with larvae growing from the onset of exogenous feeding (0.8 cm SL) to 3.8 cm SL, and sharp increments of IE appeared at around 1.2 and 2.8 cm SL. However, the same pattern was not shown in AE and UE. Except for the rapid improvement in early stage larvae (0.8 to 1.2 cm SL), AE and UE did not show any significant increase with development of larvae. ME appeared independent of the larval development. These results demonstrate that ingestion rather than assimilation affected the acceptability of Spirulina in larval tilapia. Larval tilapia could efficiently assimilate and utilize the ingested Spirulina from onset of exogenous feeding. The so-called transition of feeding habit is the feeding strategy of the larval and early stage juvenile tilapia.