The Assessment of Dietary Organic Zinc on Zinc Homeostasis, Antioxidant Capacity, Immune Response, Glycolysis and Intestinal Microbiota in White Shrimp (Litopenaeus vannamei Boone, 1931)

Abstract

This study aimed to assess dietary organic zinc on zinc homeostasis, antioxidant capacity, immune response, glycolysis and intestinal microbiota in white shrimp (Litopenaeus vannamei Boone, 1931). Six experimental diets were formulated: Control, zinc free; S120, 120 mg·kg^-1 zinc from ZnSO₄·7H₂O added into control diet; O30, O60, O90 and O120, 30, 60, 90 and 120 mg·kg^-1 zinc from Zn-proteinate added into control diet, respectively. The results showed that organic zinc significantly promoted zinc content and gene expression of ZnT1, ZIP11 and MT in the hepatopancreas and enhanced antioxidant capacity and immunity (in terms of increased activities of T-SOD, Cu/Zn SOD, PO, LZM, decreased content of MDA, upregulated expressions of GST, G6PDH, ProPO, LZM and Hemo, and increased resistance to Vibrio parahaemolyticus). Organic zinc significantly upregulated GluT1 expression in the intestine, increased glucose content of plasma and GCK, PFK and PDH activities of hepatopancreas, and decreased pyruvate content of hepatopancreas. Organic zinc improved intestinal microbiota communities, increased the abundance of potentially beneficial bacteria and decreased the abundance of potential pathogens. Inorganic zinc (S120) also had positive effects, but organic zinc (as low as O60) could achieve better effects. Overall, organic zinc had a higher bioavailability and was a more beneficial zinc resource than inorganic zinc in shrimp feeds.

Keywords: Litopenaeus vannamei Boone, 1931; antioxidants; glycolysis; immunity; intestinal microbiota; organic zinc; zinc homeostasis.

Figure 1

Effects of organic and inorganic zinc on zinc accumulation of Litopenaeus vannamei Boone, 1931 tissues (A) and gene expressions of zinc transport in hepatopancreas of L. vannamei (B). ZnT1, zinc transporter 1; ZIP11, zinc transporter ZIP11, MT, metallothionein. Values represented are means ± S.E. of 4 replicate tanks. ^a,b,c,d Value bars not sharing the same superscript letter are significantly different (p < 0.05).

Figure 2

Effects of organic and inorganic zinc on antioxidant capacity of L. vannamei. (A) enzyme activities of plasma; (B) enzyme activities of hepatopancreas; (C) gene expressions of hepatopancreas. SOD, super dismutase; CAT, catalase; T-AOC, total antioxidant capacity; MDA, malondialdehyde; Gpx, glutathione peroxidase; GST, glutathione S-transferase; G6PDH, glucose-6-phosphate dehydrogenase. Values represented are means ± S.E. of 4 replicate tanks. ^a,b,c,d,e Value bars not sharing the same superscript letter are significantly different (p < 0.05).

Figure 3

Effects of organic and inorganic zinc on immunity of L. vannamei. (A) enzyme activities of plasma; (B) gene expressions of hepatopancreas. (C) Vibrio parahaemolyticus challenge test of shrimp. ACP, acid phosphatase; AKP, alkaline phosphatase; PO, phenoloxidase; LZM: lysozyme; ProPO, pro-phenoloxidase; Hemo, hemocyanin. Values represented by A and B are means ± S.E. of 4 replicate tanks. Values represented by C are means ± S.E. of 3 replicate tanks. ^a,b,c,d Value bars not sharing the same superscript letter are significantly different (p < 0.05).

Figure 4

Effects of organic and inorganic zinc on transport and glycolysis of L. vannamei. (A) GluT1 expression of intestine; (B) Glu content of plasma; (C) enzyme activities of hepatopancreas. Glu, glucose; GluT1, glucose transporter 1; GCK, glucokinase; PFK, phosphofructokinase; PDH, pyruvate dehydrogenase. Values represented are means ± S.E. of 4 replicate tanks. ^a,b,c,d Value bars not sharing the same superscript letter are significantly different (p < 0.05).

Figure 5

Effects of organic and inorganic zinc on intestinal microbiota of L. vannamei. Taxonomy classification of reads at phylum (A) and genus (B) levels. Only top 10 most abundant (based on relative abundance) bacterial phyla and genera were shown in the figures, other phyla and genera were all assigned as ‘Others’. Flower diagram of intestinal microbiota among all groups (C). UPGMA clustering trees in groups (D) and principal coordinate analysis (PCoA) plot in samples (E) based on unweighted UniFrac distances among all groups.

Figure 5

Effects of organic and inorganic zinc on intestinal microbiota of L. vannamei. Taxonomy classification of reads at phylum (A) and genus (B) levels. Only top 10 most abundant (based on relative abundance) bacterial phyla and genera were shown in the figures, other phyla and genera were all assigned as ‘Others’. Flower diagram of intestinal microbiota among all groups (C). UPGMA clustering trees in groups (D) and principal coordinate analysis (PCoA) plot in samples (E) based on unweighted UniFrac distances among all groups.

Figure 6

MetaStat analysis of intestinal microbiota communities at genus level of shrimp among control, S120, O60 and O120 groups. (A–D) potentially beneficial bacteria of shrimp intestine; (E–H) potentially pathogens of shrimp intestine. ^a,b,c Value bars not sharing the same superscript letter are significantly different (Q < 0.05). “N” means the abundance of genus is too low to get a value at a certain number or the genus does not exist.

Figure 6

MetaStat analysis of intestinal microbiota communities at genus level of shrimp among control, S120, O60 and O120 groups. (A–D) potentially beneficial bacteria of shrimp intestine; (E–H) potentially pathogens of shrimp intestine. ^a,b,c Value bars not sharing the same superscript letter are significantly different (Q < 0.05). “N” means the abundance of genus is too low to get a value at a certain number or the genus does not exist.