| This experiment aimed to evaluate the effects of forage with different concentrate ratio on gastrointestinal tract health in 3-month-old male Dumong Lambs and to explore the mechanisms of gastrointestinal tract health of lambs with different dietary structure by detecting mucosal epithelial tissue morphology,epithelial inflammatory factors,expression levels of tight junction protein and expression levels of key enzymes in NF-κB/MAPK signaling pathway,which provide theoretical basis for lamb healthy breeding.A total of 30 Dumont male lambs(3-month-old)with body weight of(25±2.14)kg were randomly assigned to 3 treatments with 10 lambs each,which were offered basal diets with different concentrate ratio of 30:70(Group C30),50:50(Group C50)and70:30(Group C70)respectively.An acclimation period of 15 days were allowed for lamb adaptation to the pen,followed by a formal experimental session(d16-76).In the experimental period,Lambs were housed in a single column,to ensure a comfortable environment,and orderly cleaning for individual feeding to minimize stress responses,and fed with with mixed concentrate,coarse and the whole diet at 08:00 and 18:00.At the end of the experiment,5 lambs in each group were randomly selected for slaughter,the tissue samples from rumen abdominal bursa and duodenum,jejunum and ileum were collected for tissue sections.Epithelial tissues of the above gastrointestinal tract were also selected and gastrointestinal mucosa was separated for test detection.The test results show that:(1)Production performance results showed as follows,the final weight and average daily gain of C50 and C70 groups were significantly higher than those of C30 group(P <0.05),C50 group was slightly higher than C70 group;The average daily feed intake of C50 group was significantly higher than that of C30 and C70 groups(P < 0.05).The feed/gain in C50 and C70 groups was significantly lower than that in C30 group(P <0.05).The results of p H detection at different periods showed that rumen p H in C70 group was significantly lower than that in C30 group at 2 h,and p H showed a decreasing trend at the same time with the increase of concentrate proportion.(2)The gastrointestinal histological results showed that the papillary height of C70 group was significantly higher than that of C30 and C50 groups(P < 0.05),and the papillary area of the three groups showed a gradual increasing trend.The villus height of duodenum,jejunum and ileum in C70 group was significantly higher than that in C30 and C50 groups,and the crypt depth of duodenum and jejunum in C50 group was significantly higher than that in C30 and C50 groups(P < 0.05),and the crypt depth of jejunum and ileum in C70 group was significantly higher than that in C30 and C50groups(P < 0.05).The jejunum ratio in C70 group was significantly higher than that in C30 group(P < 0.05),but there was no significant difference between C50 group and C30 group,but the ileum ratio in C30 group and C50 group was significantly higher than that in C70 group(P < 0.05).The other indexes had no significant difference(P > 0.05).(3)The results showed that the m RNA expression levels and contents of IL-6,TNF-α and IFN-γ in C70 group were significantly higher than those in C30 and C50groups(P < 0.05).The m RNA expression level of IL-1β in C50 and C70 groups was significantly higher than that in C30 group(P < 0.05),the IL-1β content in C70 group was significantly higher than that in C50 group(P < 0.05),and the m RNA expression level and content of TNF-α in C70 group was significantly higher than that in C30 and C50 groups(P < 0.05).The m RNA expression level and content of IFN-γ in C70 group were significantly higher than those in C30 group(P < 0.05)and C50 group were not significantly different.The m RNA expression levels and contents of inflammatory cytokines in jejunum epithelium showed that IL-1β,IL-6 and INF-γ in C70 group were significantly higher than those in C30 and C50 groups(P < 0.05).The m RNA expression level and content of IL-1β,TNF-α and INF-γ in C70 group were significantly higher than those in C30 and C50 groups(P < 0.05),and the m RNA expression level and content of IL-10 in C70 group were significantly lower than those in C30 and C50 groups(P <0.05).(4)Gastrointestinal epithelial tight junction protein expression showed that the m RNA and protein expression level of Occludin in C70 group was significantly higher than that in C30 group(P < 0.05),and the m RNA and protein expression level of Claudin-1 in C50 group was significantly higher than that in C30 and C70 groups(P <0.05).The m RNA and protein expression levels of Occludin and ZO-1 in duodenal epithelium of lambs in C50 group were significantly higher than those in C70 group(P <0.05);The m RNA and protein expression of Occludin in C50 group was significantly higher than that in C30 and C70 groups(P < 0.05),and the ZO-1 m RNA and protein expression in C30 and C50 groups was significantly higher than that in C70 group(P <0.05).The m RNA and protein expression of Occludin in ileum in C70 group was significantly higher than that in C30 and C50 groups(P < 0.05),and the m RNA and protein expression of Claudin-1 in C50 group was significantly higher than that in C30 and C70 groups(P < 0.05).(5)The key enzymes of NF-κB signaling pathway showed that the phosphorylation levels of NF-κB p65 and IκB-α in rumen and duodenum of C70 group were significantly higher than those of C30 and C50 groups(P < 0.05).The phosphorylation level of IκB-αprotein in jejunum and ileum in C70 group was significantly higher than that in C30 and C50 groups(P < 0.05).Key enzymes of MAPK signaling pathway are shown as follows:The JNK protein phosphorylation level in rumen C70 group was significantly higher than that in C30 group(P < 0.05),the ERK and JNK protein phosphorylation levels in duodenum C70 group were significantly higher than those in C30 and C50 groups(P <0.05),and JNK protein phosphorylation levels in C50 group were significantly higher than those in C30 group(P < 0.05).The phosphorylation levels of p38 MAPK and JNK protein in jejunum C70 group were significantly higher than those in C30 and C50groups(P < 0.05).In conclusion,Dumeng lambs were fed with three different concentrate to forage ratios,and the 70:30 concentrate to forage ratio diet increased the expression levels of gastrointestinal morphology,epithelial inflammatory factors and key enzymes of NF-κB/MAPK signaling pathway.The expression of gastrointestinal epithelial tight junction protein gene and protein was better in the 50:50 concentrate to concentrate ratio diet,while the performance indexes of the 30:70 group were lower than those of the other two groups. |
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