Effect of dietary supplementation of crude microalgal extracts on growth performance, survival and disease resistance of Lates calcarifer (Bloch, 1790) larvae

The present study aimed to assess growth performance and health status of Lates calcarifer larvae fed with crude microalgal extracts. Larvae weighing 5.96 ± 0.39 mg were randomly divided into four experimental groups in triplicates, with each replicate having 35 larvae. Four diets formulated to contain 55% protein and 12% lipid, were prepared with pigment rich microalgal extracts at 0% (T1) and 1% each of crude phycocyanin (T2), chlorophyll (T3) and astaxanthin (T4) extracts. The experiment was carried out in 30 l plastic tanks by feeding experimental diets to satiation. There was no significant difference (p<0.05) in growth performance in larval groups fed different experimental diets. Percentage survival during the feeding experiment was significantly higher in the astaxanthin fed group (77.14±1.65) and lower in chlorophyll fed group (36.19±0.95) compared to control group. Cannibalism (%) was significantly reduced in the treatments fed astaxanthin (7.61±0.95) and phycocyanin (8.57±0.3) pigmented diets compared to chlorophyll fed group (13.33±0.95) and control group. Bacterial challenge with pathogenic Vibrio alginolyticus revealed highest resistance in astaxanthin and phycocyanin fed larvae. The study confirms that astaxanthin and phycocyanin at 1% dietary levels improve survival and disease resistance in Asian seabass larvae but do not affect growth performance.