The effect of binder composition on ingestion and assimilation of microbound diets (MBD) by barramundi Lates calcarifer Bloch larvae

Using ₁₄C-labelled microbound diets (MBD), five different binders were assessed for ingestion, assimilation and assimilation efficiency (AE) when fed to 18 day-old barramundi Lates calcarifer Bloch larvae. MBD bound with alginate and zein were ingested to the highest degree; however, the AE of these two diets was low. Diets bound with gelatin and carrageenan exhibited high AE, although ingestion was significantly lower than for alginate- and zein-bound diets. Combining two binders with different ingestion and assimilation characteristics was investigated as a means of improving diet performance. A diet bound with a 1:1 ratio of gelatin and alginate resulted in greater ingestion than MBD bound with gelatin alone and a higher AE than MBD bound with alginate alone. A third experiment investigated the effects of decreasing binder concentration on ingestion, assimilation and nutrient leaching. Alginate and gelatin were tested at concentrations of 1%, 2% and 3% of the dry weight of the MBD. No significant differences were detected in the ingestion or assimilation rates of the diets bound with different binder concentrations. Leaching losses from MBD containing 1% binder were significantly higher than those bound with 2% or 3% binder. It was concluded that either gelatin or carrageenan at 2-3% inclusion would be a suitable binder in weaning diets for barramundi larvae.