Abstract: The aim of this study was to investigate the effects of dietary L-malic acid supplementation on intestinal health and inflammatory response of weaned piglets. A total of 192 healthy 28-day-old crossbred (Duroc×Landrace×Yorkshire) weaned piglets (initial body weight (9.12±0.52) kg) were randomly divided into 4 treatments, with 6 replicates per treatment and 8 piglets per replicate. The control group was fed a corn-soybean meal based diet, and the three treatment groups were fed the basal diet supplemented with 0.25%, 0.5% and 1% L-malic acid products (containing 20% L-malic acid and 80% carrier) for 28 days, respectively. Levels of circulating inflammatory factors were detected on days 14 and 28. Moreover, the inflammatory response, antioxidant capacity and jejunum morphology of piglets were measured after slaughter, and protein expression levels related to barrier function in jejunum were analyzed as well. The results showed as follows: 1) Compared with the control group, diet supplemented with 1% L-malate products significantly decreased the levels of pro-inflammatory factors tumor necrosis factor -α (TNF-α) and interleukin-6 (IL-6) in plasma of piglets on day 14 (P<0.01), and significantly increased the level of anti-inflammatory factor interleukin-10 (IL-10) (P<0.01). Plasma IL-6 level was significantly decreased (P<0.01) and plasma IL-10 level was significantly increased (P<0.01) on the 28th day of the experiment. This suggests that dietary supplementation with 1% L-malate product alleviates the inflammatory response of weaned piglets. 2) Dietary 1% L-malic acid product significantly decreased the levels of TNF-α, interferon-γ (IFN-γ) and IL-6 in jejunum mucosa (P<0.05 or P<0.01), and significantly increased the level of IL-10 (P<0.01). Meanwhile, L-malic acid product markedly increased the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) and the level of total antioxidant capacity (T-AOC) in jejunum mucosa (P<0.05 or P<0.01), and also decreased the malondialdehyde (MDA) level significantly (P<0.05). 3) L-malic acid supplementation significantly increased the villus height of jejunum (P<0.01) and thus elevated the ratio of villus height to crypt depth (P<0.05). 4) Compared with the control group, L-malic acid supplementation tended to increase the protein expression level of Occludin (P=0.07) and decreased the protein expression level of Claudin-3 significantly (P<0.01). In conclusion, dietary supplementation of 1% L-malic acid product can improve the anti-inflammatory capacity of weaned piglets. Importantly, 1% L-malic acid supplementation can improve the anti-inflammatory and antioxidant capacity of jejunum, improve digestion and absorption function, and thus improve intestinal health, but the effect on intestinal barrier function needs further research.

Key words: L-malic acid, weaned piglets, inflammatory response, antioxidant capaticy, barrier function, jejunum