Dietary replacement of Undaria pinnatifida by Sargassum horneri in feed formulation for abalone Haliotis discus hannai: Effect on growth, gut microbiota, and taste sensory profile

The necessity for additional macroalgal biomass is warranted amid the ongoing expansion of abalone aquaculture. In the current study, an in-depth investigation of the food value of Sargassum horneri as a replacement for Undaria pinnatifida on growth, body composition, body histology, gut microbiota, and the taste sensory profile of abalone Haliotis discus hannai was carried out. After a 12-week feeding trial, the results indicated that 25% replacement (SH25) induced the highest shell-growth performance and best feed utilization values, although there was no significant difference in weight-related growth parameters with the basal (no inclusion of S. horneri) and 50% replacement (SH50) diets. Interestingly, the highest protein content was detected in abalone fed the basal diet followed by SH25 and SH50. The high replacement of S. horneri in the diet showed signs of structural integrity loss in the digestive gland. The results from the pyrosequencing of the genomic DNA from the gut of the abalone indicated an insignificant difference in α-diversity parameters and only a clear boundary was observed between SH0 and SH100 diets based on principal coordinate analysis. The bacterial genera Psychrilobacter, Vibrio, and Mycoplasma predominantly occupied the gut of the abalone, although there is a difference in their relative abundance. The taste screening experiment through the use of an electronic tongue showed a comparable taste profile of the abalone and is independent of the diets given. The findings of the present study showed that S. horneri, up to 50% replacement of macroalgal ingredients, can be utilized in feed formulation for H. discus hannai. These, in turn, contribute to the expanding knowledge on the utilization of biofouling and non-traditional macroalgae for sustainable abalone aquaculture practices.