Organic manganese as a functional micronutrient: Promoting metabolic health and sustainable growth in Litopenaeus vannamei

Abstract

This study evaluated the effects of five manganese (Mn) sources on Pacific white shrimp (Litopenaeus vannamei). Five Mn sources include Mn sulfate (MnSO4·H2O), Mn dioxide (MnO2), Mn dioxide nanoparticles (MnO2NPs), Mn glycine chelate (Mn-Gly), and Mn chelate of hydroxy analogue of methionine (Mn-MHA). During a 56-d feeding trial, 450 shrimp (1.03 ± 0.02 g) were randomly distributed among five dietary treatments, with each having three replicates. Growth performance and feed utilisation were not observed to be significantly affected by Mn sources (P > 0.05). However, organic Mn sources (Mn−Gly and Mn−MHA) significantly enhanced Mn deposition (P = 0.002) and upregulated a key Mn transporter (zip14, tmem165, and fpn1) in the hepatopancreas when compared with inorganic MnO2 source (P < 0.05). Moreover, dietary organic Mn-MHA significantly enhanced systemic antioxidant capacity (T-AOC and GSH-Px) and innate immune response, as evidenced by increased activities of relevant enzymes (AKP, ACP, and NOS) and upregulation of associated genes (gpx, cat, sod, nos, and akp) when compared with MnO2 (P < 0.05). Furthermore, the organic Mn sources significantly downregulated genes related to endoplasmic reticulum stress (perk, atf4, atf6, and eif2α), inflammation (spz-5, il-16, and rab6a), and apoptosis (caspase8, p53, and caspase3), while significantly upregulating the anti-apoptotic gene (bl-1) when compared with MnO2 (P < 0.05). Notably, Mn−MHA supplementation significantly reduced hepatopancreatic lipid content (P = 0.002) by modulating the expression of genes involved in lipid synthesis (fas and acc) and lipolysis (aco and cpt) (P < 0.05). In summary, although growth remained unaffected, organic Mn sources, particularly Mn−Gly and Mn−MHA, demonstrated superior bioavailability by enhancing antioxidant status, immune function, and hepatopancreas health as well as by regulating lipid metabolism.