Dietary 25-hydroxyvitamin D improves productive performance and intestinal health of laying hens under Escherichia coli lipopolysaccharide challenge

The effect of 25-hydroxyvitamin D (25OHD) on the immune response of laying hens is not well elucidated. This study investigated the effects of 25OHD on egg production, egg quality, immune response, and intestinal health of laying hens challenged with Escherichia coli lipopolysaccharide (LPS). One hundred and sixty laying hens at 45 wk of age were randomly divided into 4 dietary treatments with 10 replicates of 4 birds. Hens were fed the corn-soybean based diets contained either 0 or 80 µg/kg 25OHD for 8 wks. At wk of 53 wk, birds of each dietary treatment were injected into the abdomen with 1.5 mg/kg body weight of either LPS or saline a day at 24-h intervals for continuous 7 d. LPS injection significantly decreased (P(LPS) < 0.05) egg laying rate, feed intake and feed efficiency; while the supplementation of 25OHD increased (P(Interaction) < 0.05) egg laying rate, feed efficiency and decreased (P(Interaction) < 0.05) the broken egg rate in layers under LPS injection. LPS challenge decreased (P(LPS) < 0.05) eggshell strength, eggshell thickness, albumen height and Haugh unit, while dietary 25OHD supplementation increased eggshell strength and eggshell thickness (P(25OHD) < 0.05). The serum proinflammatory factors [tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6)], endotoxin and diamine oxidase (DAO) levels were higher in layers under LPS challenge (P(LPS) < 0.05); whereas the dietary addition of 25OHD were shown to decrease (P(25OHD) < 0.05) serum IL-1β and IL-6 concentration irrespective of LPS challenge and led to a higher serum 25OHD level and a reduction in endotoxin concentration in layers under LPS challenge (P(Interaction) < 0.05). The layers under LPS challenge had higher crypt depth and lower villus height/crypt depth (V/C) ratio in duodenum and jejunum (P(LPS) < 0.05), while feeding 25OHD were shown to have decreasing effect on crypt depth and increasing effect V/C ratio in layers under LPS challenge (P(Interaction) < 0.05). Layers under LPS challenge had lower mRNA expression of intestinal barrier associated proteins (claudin-1 and mucin-1) (P(LPS) < 0.05), while the addition of 25OHD up-regulated claudin-1 and mucin-1 expression (P(interaction) < 0.05). Lower antioxidant enzymes activities, including superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), glutathione peroxidase (GPx) and higher malondialdehyde (MDA) content in jejunum were found in layers challenged with LPS (P(25OHD) < 0.05). The effect of 25OHD reversed the effect of LPS on SOD, T-AOC, and MDA content (P(Interaction)< 0.05). These results suggest that supplementing 80 µg/kg 25OHD in diets may elevate laying performance and egg quality through the improvement of intestinal barrier function, antioxidant capacity, and decreased the proinflammatory cytokines levels in laying hens with Escherichia coli LPS challenge.