Effects of dietary licorice extract on serum Biochemical index, tissues antioxidant capacity and immunity function of weaned piglets

Abstract Background: This study investigated the effects of dietary licorice extract (LE) on antioxidant capacity and immunity in weaned piglets. A total of 96 DLY (Duroc × Landrace × Yorkshire) weaned piglets were randomly assigned to four treatments. The control group were fed a corn–soybean meal-based diet (basal diet, BD), and three LE level groups were fed on BD supplied with 50、150 and 250 mg/kg LE. The trial lasted 5 weeks. At day 35, six piglets per treatment were killed and blood, liver, spleen, and thymus were collected.Results: The result showed that: 1)Dietary LE increased (P < 0.05) activity of the alkaline phosphatase (ALP) and reduced (P < 0.05) the activity of glutamic oxalacetic transaminase (AST), 50 mg / kg LE reduced (P < 0.05) total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) in serum. 2) The addition of 150 and 250 mg / kg LE increased (P < 0.05) glutathion peroxidase (GSH-Px) activity in liver and spleen, increased (P < 0.05) the total antioxidant capacity (T-AOC) in serum and spleen . 50 mg / kg LE increased (P < 0.05) the total superoxide dismutase (T-SOD) activity in serum. Three doses of LE reduced (P < 0.05) serum malondialdehyde content (MDA). 3) 150 mg / kg LE increased (P < 0.05) serum IgG level. 4) Dietary LE down-regulated (P < 0.05) the mRNA levels of 7 immune-related genes (IL-6, IL-8, IL-10, IL-1β, TNF-α, MCP-1, ICAM-1) in the thymus; 50 mg / kg LE and 150 mg / kg LE down-regulated (P < 0.05) the mRNA levels of TNF-α, while 250 mg / kg LE up-regulated the mRNA levels of 2 inflammatory genes (IL-1β, and ICAM-1) in the spleen; three levels of LE down-regulated (P < 0.05 the mRNA levels of 3 inflammatory genes (IL-6, TNF-α, ICAM-1) in the liver.Conclusions: In summary, LE supplementation regulates the activity of serum biochemical enzyme, improves the antioxidant capacity and immune function of in serum, liver, spleen and thymus, those improvement may contributes to the promotion of growth performance of weaned piglets. In general, 150 mg / kg LE exhibits better effect.