Zinc has been extensively studied in aquafeeds and some studies suggested that it may be a promising candidate additive in shrimp feed to improve immunity and antioxidant capacity.
Zinpro, together with British and Chinese researchers, conducted an eight-week feeding trial to evaluate the effects of dietary organic zinc (zinc amino acid chelate) on growth performance, mineral bioaccumulation in the whole body, hepatopancreas and carapace, innate immune response and antioxidant capacity of juvenile Pacific white shrimp Litopenaeus vannamei. Five isonitrogenous and isolipidic diets were formulated to contain different zinc levels of 46.4 (basal diet), 65.5, 85.9, 108.4 and 130.6 mg kg−1.
Dietary zinc levels significantly influenced growth and feed utilization, with the lowest weight gain and highest feed conversion ratio observed in shrimp fed the basal diet. The study estimates that the optimal dietary zinc requirement is 104.8 mg kg-1 for juvenile Pacific white shrimp. Shrimp fed the diet containing 130.6 mg kg−1 Zn had the highest zinc concentration in hepatopancreas and carapace, but there were no significant differences in calcium or phosphorus concentration in tissues.
Dietary Zn increased the activities of lysozyme, alkaline phosphatase and polyphenol oxidase in hepatopancreas. Shrimp fed the diets supplemented with zinc had significantly higher activity of Cu/Zn SOD and lower content of malondialdehyde in hepatopancreas. The expression levels of toll, imd, lzm, proPO and alp involved in immunity and Cu/Zn sod related to oxidation resistance were up-regulated. Zinc also promoted the expression levels of mt and mtf-1, and up-regulated the expression of SLC39 family genes (zip3, zip9, zip11, zip14) in the hepatopancreas.
“The optimal zinc requirement was estimated to be 104.8 mg kg−1 (∼10.5 μg g−1 body weight) for juvenile Pacific white shrimp. Feeding diets with 108.4-130.6 mg kg−1 Zn could maintain normal immune responses and antioxidant ability,” researchers concluded. “These data provided novel insights in the potential mechanism of organic zinc-induced enhancement of immunity and antioxidant capacity in Pacific white shrimp.”
Read the study here.
