Chitosan oligosaccharide (COS), an oligomer of D-glucosamine, is a vital growth stimulant in the pig industry. However, the mechanisms by which COS mediates pig growth are not fully understood. Therefore, we further investigated how COS supplementation affects pig growth. A total of 32 Landrace × Yorkshire weaned pigs were randomly divided into a control group (basal diet without COS supplementation) and a COS group (100 mg COS per kg basal diet). The pigs that ingested COS for 21 days were associated with a higher (P < 0.05) average daily body weight gain compared to those in the control group. Relative to the control group, the apparent digestibility of crude protein, ash, fat, dry matter and gross energy were markedly elevated (P < 0.05) upon COS supplementation. COS supplementation not only increased (P < 0.05) the activities of superoxide dismutase, catalase and total antioxidant capacity but also elevated (P < 0.05) interleukin-6, tumour necrosis factor-α and immunoglobulin G concentrations in the serum. Moreover, the serum malondialdehyde concentration was decreased (P < 0.05) 26.59% by COS ingestion. COS supplementation also significantly enhanced (P < 0.05) secretory immunoglobulin A content, villus height and digestive enzyme activities (maltase, lactase and sucrase) in the small intestine. Intriguingly, dietary COS supplementation up-regulated (P < 0.05) the tight junction protein claudin-1 (CLDN-1) and occludin (OCLN) mRNA abundance, as well as the Na⁺–glucose co-transporter 1 (SGLT1) mRNA abundance in the jejunum. Importantly, COS not only increased (P < 0.05) the Bifidobacterium populations in the ileum but also decreased (P < 0.05) the total bacteria and Escherichia coli populations in the caecum and colon. Together, these results suggest that COS supplementation can accelerate weaned pig growth through enhancing antioxidant and immune properties, as well as intestinal development.

Alginate oligosaccharide (AOS), produced from alginate by alginate lyase-mediated depolymerisation, is a potential substitute for antibiotics and possesses growth-enhancing effects. Nevertheless, the mechanisms by which AOS regulates porcine growth remain to be elucidated. Therefore, we investigated the AOS-mediated changes in the growth performance of weaned pigs by determining the intestinal morphology, barrier function, as well as epithelium apoptosis. Twenty-four weaned pigs were distributed into two groups (n = 12) and received either a basal diet (control group) or the same diet supplemented with 100 mg/kg AOS. On d 15, D-xylose (0.1 g/kg body weight) was orally administrated to eight randomly selected pigs per treatment, and their serum and intestinal mucosa samples were collected 1 h later. Our results showed that inclusion of AOS in the diet for 2 wk increased (P < 0.05) the average daily body weight gain in weaned pigs. Notably, AOS supplementation ameliorated the intestinal morphology and barrier function, as suggested by the enhanced (P < 0.05) intestinal villus height, secretory immunoglobulin A content and goblet cell counts. Compared to the control group, AOS ingestion both decreased (P < 0.05) the total apoptotic percentage and increased (P < 0.05) the proportion of S phase in the intestinal epithelial cells. Furthermore, AOS not only up-regulated (P < 0.05) the B-cell lymphoma-2 (BCL2) transcriptional level but also down-regulated (P < 0.05) the B-cell lymphoma-2-associated X protein (BAX), cysteinyl aspartate-specific proteinase-3 (caspase-3) and caspase-9 transcriptional levels in the small intestine. In summary, this study provides evidence that supplemental AOS beneficially affects the growth performance of weaned pigs, which may result from the improved intestinal morphology and barrier function, as well as the inhibited enterocyte death, through reducing apoptosis via mitochondria-dependent apoptosis.

Alginate oligosaccharide (AOS), prepared from depolymerised alginate, a natural polysaccharide occurring in the cell walls of brown algae, provides beneficial effects for intestinal health. However, the underlying mechanisms by which AOS supplementation maintains the intestinal integrity of weaned pigs remain obscure. Here, we aimed to determine how AOS modulates the intestinal integrity of weaned pigs. Twenty-four weaned pigs were assigned to two treatments: a control group (basal diet) and an AOS group (the basal diet supplemented with 100 mg kg⁻¹ AOS). On day 15, eight pigs per treatment were randomly selected and sacrificed for serum and intestinal samples. We observed that AOS supplementation enhanced the intestinal integrity, as evidenced by the increased (P < 0.05) intestinal occludin protein abundance. Compared to the control group, AOS ingestion both elevated (P < 0.05) the jejunal and ileal catalase activity and decreased (P < 0.05) the duodenal and jejunal tumour necrosis factor-α concentration and mast cell tryptase expression. Furthermore, AOS down-regulated (P < 0.05) the duodenal toll-like receptor 4 (TLR4) and its down-stream signals, myeloid differentiation factor 88 (MyD88), interleukin-1 receptor-associated kinase 1 (IRAK1) and tumour necrosis factor receptor-associated factor 6 (TRAF6) mRNA levels, as well as jejunal nucleotide-binding oligomerisation domain protein 1 (NOD1) and its adaptor molecule, receptor-interacting serine/threonine-protein kinase 2 (RIPK2), mRNA levels. Additionally, phospho-nuclear factor-κB (p-NF-κB) p65 protein abundance in the duodenum and jejunum was down-regulated (P < 0.05) following AOS supplementation. According to the above results, the enhanced intestinal integrity in AOS-supplemented pigs appears to be associated with the elevated antioxidant capacity and the reduced mast cell degranulation, as well as the inhibited pro-inflammatory cytokines production via inhibiting the TLR4/NF-κB and NOD1/NF-κB signalling pathways.

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.