An evaluation of the growth and immunity of New Zealand black-footed abalone (Haliotis iris) treated with encapsulated feed and probiotics

Encapsulation technology has been applied in aquaculture for developing more efficient delivery systems of nutrients and probiotics to various species. This study aims to investigate the effect of an encapsulated probiotics feed on the growth and health of New Zealand black-footed abalone (Haliotis iris). Juvenile abalone were fed with four different dietary treatments, including commercial pellets, commercial feed sprayed with probiotics, combination of commercial feed and chitosan-coated alginate (CCALG) beads containing probiotics and CCALG beads containing both probiotics and nutrients. A multi-technique approach was used to evaluate the growth performance and health parameters of the experimental animals after 57 days in feeding trial. The results showed a significantly higher growth rate (p < 0.05) in shell length (50.06 +/- 5.91 mu m/day) and weight (25.55 +/- 2.55 mg/day) of abalone fed with CCALG beads containing both probiotics and nutrients (optimal diet) compared to the other groups. The feed conversion rate (FCR) for abalone fed with the optimal diet (1.04 +/- 0.06) was significantly (p < 0.05) lower than the other experimental diets. Furthermore, a low level of haemocytes with reactive oxygen species (ROS) was found associated with the optimal diet (13.24 +/- 4.2%). A total of 31 differently regulated metabolites across the four treatments were revealed with a characteristic enhancement of free amino acids in the samples obtained from abalone fed with the optimal diet. The combined results from the growth parameters, flowcytometry and metabolomics indicate that CCALG beads encapsulating probiotics and nutrients can efficiently improve the growth and immunity of juvenile abalone.