| The aim of this experiment is to study the effects of MOS dietary supplementation on growth performance, intestinal microflora and serum immunoglobulins in laying hens subjected to high density stress. Moreover, we investigate the supplementation potential and efficiency of MOS on the promotion of the intestinal microflora and immune function. A total of 864 12-week-old Hy-Line Brown were randomly allocated to 6 treatments with 12 replicates of 3 cages each. Every cage contained 3 to 5 laying hens. The test group L0 was reared under a low density and fed with basal diet. The H0 group is same than the L0 group but under high density. The experimental group L2 was a low density group fed on basal diet supplemented with 250 g/t MOS. The H2 group was a high density group fed on basal diet supplemented with 250 g/t MOS. The experimental group L5 was a low density group fed on basal diet supplemented with 500 g/t MOS and finally the H5 group was a high density group fed on basal diet supplemented with 500 g/t MOS. The experiment lasted for 40 weeks during which the welfare, drinking, feeding and feces of each laying hen were observed. After 16, 30 and 50 weeks, one laying hen from each group was randomly selected and blood, intestinal mucosa and intestinal digesta samples were collected. The results showed that, compared with the L0 control group, a change of feed intake, egg production rate, blood glucose was perceived for the high density control group, which indirectly demonstrates that high density causes stress response. The breeding density influenced feed intake as the low density group showed significantly higher feed intake than the high density group(P < 0.05). To some extent, adding MOS reduced the high density group feed intake. Indeed, an interaction between the density and dosage of MOS treatment was perceived for the feed intake parameter. However, breeding density and MOS had no significant influence on egg laying rate and feed egg ratio. Nevertheless, the high density group showed a significant decreased in GLU, UREA and TCHO serum levels after 30 weeks. MOS could significantly improve GLU serum level and decrease TG and VLDL levels to some extent. MOS enhanced serumIgA levels after immunization(P < 0.05) and significantly reduced the endotoxin level(P <0.05). It is worth emphasizing that the most appropriate dosage was 250 g/t. The stocking density had no significant effect on IgA and endotoxin levels(P > 0.05). MOS supplementation at 250 g/t did improve the levels of oestrogen and follicle stimulating hormone while breeding density did reduce the estrogen content even though the difference was not significant. MOS significantly decreased the Escherichia coli population and increased the lactobacilli levels in the jejunum and ileum(P < 0.05). Moreover, MOS supplementation increased the villus length and decreased crypt depth rising villus length and crypt depth ratio. However, the stocking density had little effect on the intestinal flora and intestinal villus length. Nevertheless, the stocking density promoted the expression of duodenal occludin and claudin-1(P < 0.05) as well as the expression of claudin-1 in ileum(P< 0.05) after 16 weeks. The stocking density also significantly reduced the content of TLR4 in duodenum and ileum, the content of TLR5 in ileum was also reduced although its effect on the expression of jejunum toll receptors and nutrient transport carriers in ileum at 30 weeks was no significant. Conclusion: MOS can promote the intestinal mucosal structure recovery and development through a well-balanced intestinal microflora, a decreased toxicity due to intestinal endotoxin, an increased immunoglobulin secretion, an improved body immunity, an appropriate reproductive hormone secretion and finally a reduced stress response caused by high breeding density. The recommended MOS supplementation dosage is 250g/t MOS. |
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