Nutritional Impacts of Arthrospira platensis Nanoparticles on Growth, Intestinal and Liver Histology, Antioxidant Status, and Immunological Response in Mullet (Mugil cephalus).

This study investigates the impact of dietary supplementation with nanoparticles of Arthrospira platensis (previously known as Spirulina platensis) on the performance of the mullet Mugil cephalus during a 63-day feeding trial. Fish (14.75 ± 0.23 g/fish) were randomly distributed into five groups of 30 fish per hapa, with three replicates per group. Five experimental diets were prepared to assess nano-A. platensis supplementation at three inclusion levels: 0.5, 5, and 10 g/kg (SN0.05%, SN0.5%, and SN1%). Two control groups were included for comparison: a negative control without additives (S0%) and a positive control with 1% non-nanoform A. platensis (S1%). Among all SN groups, the fish fed the SN0.05% diet showed significant (p ≤ 0.05) values for final weight (FW), specific growth rate (SGR), weight gain (WG), feed conversion ratio (FCR), protein efficiency ratio (PER), and feed efficiency ratio (FER). Also, the middle intestine showed marked improvements (p ≤ 0.05) in villus height and width, muscularis mucosa thickness, and the number of goblet cells when fish were fed the various SN levels or the S1% diet. Moreover, fish treated with A. platensis nanoparticles showed a noticeable enhancement in hepatic histomorphology, with the SN0.05% group exhibiting the most intact hepatic structure. However, the S0% diet had the highest alanine aminotransferase (ALT) and aspartate aminotransferase (AST) compared to other diets supplemented with different A. platensis levels. No significant difference (p > 0.05) in albumin levels was observed. Non-nano A. platensis improved immunoglobulin M (IgM) activity compared with the control (S0%). The nanoform diets resulted in the highest lysozyme (LYZ) activity, with the SN0.05% treatment showing the highest values of all groups. Fish fed A. platensis, either as nanoparticles or in its non-nano form, showed significantly lower triglyceride and cholesterol levels (p ≤ 0.05) than those that were fed the control diet (S0%). Additionally, all diets containing either nano- or non-nanoform A. platensis (SN0.05%, SN0.5%, SN1%, and S1%) resulted in increased activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), alongside decreased malondialdehyde (MDA) levels, in comparison to S0%. In general, our findings showed that A. platensis nanoparticles improve M. cephalus growth performance, intestinal and hepatic histomorphology, immune response, feed utilization, and antioxidant enzyme activity. Therefore, nano-A. platensis could be an efficient feed additive for M. cephalus, making mullet farming more environmentally friendly and cost-effective.