Dietary Laminaria japonica Polysaccharide Regulates Systemic Defence Property of Weaned Piglets Improving Growth Performance under High Temperature Condition

Background: This study was conducted to evaluate the effect of dietary LJP supplementation on growth performance, heat stress resistance and immune status of weaned piglets raised in a high-temperature environment (34 ± 3°C).Methods: A total of 72 Barkshire × Licha Black crossbred piglets were weaned at 30 days of age (BW, 5.88 ± 0.16 kg) and fed either without or with 100, 200 or 400 mg/kg LJP in a completely randomized design, with 3 pens per diet (6 pigs per pen). On day 21, a total of 12 piglets were selected to collect blood samples.Result: The results showed that 200 and 400 mg/kg LJP supplementation decreased the feed conversion ratio (FCR) of piglets compared to the control group (P = 0.037) and dietary LJP linearly increased average daily gain and decreased FCR of piglets (P = 0.037 and 0.011, respectively). In addition, adding 100, 200 and 400 mg/kg LJP reduced the serum HSP70 content compared to the control group (P = 0.019) and dietary LJP linearly and quadratically decreased the serum HSP70 content of piglets (P = 0.030 and 0.011, respectively). Moreover, supplementation of 200 mg/kg and 400 mg/kg LJP increased the serum (NO) and nitric oxide acid phosphatase (ACP) content compared to the control group (P = 0.019; P = 0.003) and dietary LJP linearly increased the serum lysozyme, NO and ACP contents (P = 0.039; P = 0.005; P = 0.001). In conclusion, dietary LJP has potential to regulate systemic defence property of weaned piglets raised in a high temperature condition, accompanied by increased growth performance.