Alginic acid oligosaccharide accelerates weaned pig growth through regulating antioxidant capacity, immunity and intestinal development

Alginic acid oligosaccharide (ALGO) is the lyase–lysate of alginic acid, which is a naturally occurring anionic polysaccharide isolated from the cell walls of seaweed. In the present study, we fully characterised the effects of dietary ALGO supplementation on certain parameters of weaned pigs. In a 21-day experiment, 16 Landrace × Yorkshire weaned pigs were divided into two groups (n = 8) and fed either with a corn–soybean basal diet (CON) or a basal diet supplemented with 100 mg kg⁻¹ ALGO. We show that dietary ALGO supplementation markedly enhanced (P < 0.05) the average daily body weight gain (ADG) of weaned pigs over the experimental periods. ALGO supplementation not only elevated (P < 0.05) the concentrations of IL-10, IgG and IgA but also increased (P < 0.05) the activities of superoxide dismutase (SOD), catalase (CAT) and total antioxidant capacity (T-AOC) in the serum. Moreover, the concentration of serum malonic dialdehyde (MDA) was lower (P < 0.05) in the ALGO group than in the CON group. ALGO supplementation also significantly enhanced (P < 0.05) secretory immunoglobulin A (sIgA) content, villus height and disaccharidase activities (lactase and sucrase) in the small intestine. Interestingly, dietary ALGO supplementation up-regulated (P < 0.05) the expression levels of tight junction protein occludin (OCLN) and zonula occludens 1 (ZO-1) in the small intestine. Importantly, ALGO not only increased (P < 0.05) the populations of Bifidobacterium and Lactobacillus but also decreased (P < 0.05) the populations of total bacteria and Escherichia coli in the intestine. Overall, the positive effects of ALGO on the growth performance, antioxidant capacity, immunity and intestinal development in weaned pigs suggest that ALGO could serve as an attractive bioactive feed additive in the pig industry, which may be beneficial to human health.