Effect Of Lipopolysaccharide And Dexamethasone Stress On Intestinal Mucosa Barrier Function In Broiler Chickens

This study was to evaluate the effect of bacterial lipopolysaccharide stress and dexamethasone stress on the growth performance, nutrient metabolism, development of organ and intestine, expression of intestinal gene and cecal microflora in broiler.128 AA broilers (1-day-old) were used and divided into four groups randomly, it included no immune group (NV), normal immune group (CV), immunosuppression group (DEX) and immune hyperthyroidism group (LPS), and there was 4 replicates in every groups and 8 broilers in one replicate. At 15 d,17 d,19 d, and 30 d,32 d,34 d,500 μg/kg BW LPS and 2.5 mg/kg-BW DEX were intramuscular injected for LPS and DEX groups, and saline was injected for NV and CV groups with the same volume. Broilers were slaughtered at 20 d,28 d,35 d and 42 d. Bursa of fabricius, spleen, thymus, liver and pancreas were collected to determine the organ index; duodenum, jejunum, ileum were sampled to observe the small intestine morphology; RT-PCR technology were conducted to determine the expression of TNF-α、TLR-4、ZO-2 and MUC-2; caecum contents in one side were gathered for bacteria count. The results showed that:average daily feed intake (ADFI) and average daily gain (ADG) were increased significantly (P<0.05) by LPS and DEX immunological stress, diets weight ratio was no significant difference (P>0.05) among groups; apparent metabolic rate of dry matter (DM), crude protein (CP), Ca and P were declined significantly (P<0.05) by LPS and DEX immunological stress, but it has no effect on organic matter (OM) apparent digestibility; wall thickness, mucosa thickness, villus height and the ratio of villus length to crypt depth were significant reduced by LPS and DEX immunological stress for 20 d and 35 d broiler; besides,35 d broiler liver index,20 d and 35 d bursa index and thymus index,20 d spleen index were all reduced significantly (P<0.05) by DEX treatment, and 28 d spleen index were promoted (P<0.05) by LPS treatment; in addition, expression of TNF-a and TLR-4 mRNA in broiler small intestinal mucosa were increased apparently (P<0.05), and expression of MUC2 and ZO-2 mRNA were declined significantly (P<0.05) by LPS and DEX immunological stress; the number of Escherichia coli (E) was increased significantly (P<0.05) and the number of Lactobacillus and Bifidobacterium (B) were reduced significantly (P<0.05) by LPS and DEX immunological stress, and the B/E value was declined simultaneously(P<0.05).In summary, LPS and DEX immunological stress has an important influence on the apparent digestibility of DM、CP、Ca and P. So, ADFI and ADG of broilers were declined because of the immune organs and the function of intestinal mucosal barrier were all damaged by LPS and DEX immunological stress.