| In modern intensive pig production system,the feeding mode of confinement can cause severe stress in pregnant sows.Because of the limited activity space of sows,sows cannot express some of the normal behaviors and cause frequent stereotyped behaviors,especially sham-chewing behavior.Many researches have also confirmed that the long-term confinement not only does harm for behaviors,physiology and immunity of pregnant sows,but also negatively affect s their emotion,even makes them have a depressive-like state and poor welfare of pregnant sows.Therefore,the purpose of this research was to study the behavioral,physiological,and immunological levels of pregnant sows with different characteristics of sham-chewing behavior under confined environment,as well as brain histomorphological change,IL-6?BDNF gene expression levels in brain tissue.In order to establish the internal relationship between the above indicators and sham-chewing behavior of sows.It builts a foundation for further revealing the physiological,immunological and brain nerve molecular mechanisms of sham-chewing behavior of sows,and provides an important theoretical basis for sham-chewing behavior as the evaluation of psychological negative state indicators of sows.Section 1:Relationship between sham-chewing behavior and other behaviors,physiology and immunity in pregnant sows under confined environmentAim to study the physiological and immunological mechanisms of sows sham-chewing behavior,this study selected 63 sows(Large-white × Landrace)with similar body conditions,and collected 24-hour behavioral data on the 21 st and 23 nd days of pregnancy period to get the high-incidence period of sham-chewing behavior.24 th and 25 th days of sham-chewing behavior data in peak period were grouped according to Analyse-Classify-Hierarchical cluster by SPSS 20.0 system.The groups were classified into three groups: sows sham-chewing behavior in the high frequency group(group H),the middle frequency group(group M)and the low frequency group(group L),respectively.Five pigs were randomly selected from the three different groups as the target sows.Collect and record behavioral data of target sows(pre-pregnancy(days 26-27),mid-pregnancy(days 61-62)and post-pregnancy(days 91-92),including general behavior(standing,sitting,ventral lying and lateral lying),and state behavior(sham-chewing behavior,bar-biting,trough-biting and rooting),blood samples were collected at one day after be havioral observation and serum physiological indicators(cortisol,Pig-MAP and CRP)and immunological indicators(Ig A,Ig G,IL-10,TNF-? and IFN-?)were detected by Enzyme-linked immunosorbent assay(ELISA).The results showed that with the increase of pre gnancy period,the standing in the group H and M decreased significantly(P=0.004;P=0.020),and group H and M were significantly lower than the post-pregnancy(P=0.040;P=0.002).Significantly lower than the post-pregnancy(P=0.003;P<0.001),in the different pregnancy period,the group H was significantly lower than the group L(P=0.044;P=0.008;P=0.024).The frequency of sham-chewing behavior was significantly reduced in the group H and M(P<0.001,P<0.001),while the group L was not significantly different(P=0.314).In the pre-pregnancy and mid-pregnancy,the difference among three groups was significant(P<0.001,P<0.001),showed that the group H was much higher than group M,and group M was much higher than group L;in the post-pregnancy,Group H and M decreased significantly,but the difference among the three groups was not significant(P=0.327).With the increase of pregnancy period,bar-biting in group H significantly increased in the post-pregnancy(P=0.018),while the rooting behavior was significantly decreased(P=0.033).The CRP in serum was significantly higher in group H than in group L during mid-pregnancy(P=0.031),and the CRP in group H was significantly lower in pre-pregnancy than that in mid-pregnancy and post-pregnancy(P<0.05).Other physiological indicators were not significantly different among different groups during pregnancy period(P>0.05).The IFN-? level in serum in group H was significantly lower than that in group L during the pregnancy period(P=0.017;P=0.050;P=0.033).In the post-pregnancy,the serum IL-10 levels in group H and group M were significantly higher than those in group L(P=0.049).The frequency of sham-chewing in group H was significantly positively correlated with the level of IL-10 in pre-pregnancy and mid-pregnancy(P=0.015;P=0.045).The frequency of sham-chewing in group M was significantly positively correlated with the level of Ig G in post-pregnancy(P=0.043)and was significantly positively correlated with the level of TNF-? in mid-pregnancy(P=0.022).Conclusion:Pregnancy sows with different characteristics of sham-chewing behavior showed different changes in standing and lateral lying behaviors.The changes of sham-chewing behavior are consistent with that of rooting behavior,while inconsistent with t hat of bar-biting and trough-biting behavior.The frequency of sham-chewing behavior reflects the higher stress level and lower immunity level of sows.Howerver,the expression of sham-chewing behavior may enhance the adaptability of sows to the confined environment.Section 2:Relationship between sham-chewing behavior and brain histomorphology changes and expression levels of IL-6?BDNF in pregnant sows under confined environmentIn order to research the histomorphological changes of brain tissue and the ex pression levels of IL-6 and BDNF genes related to stereotyped behaviors in pregnant sows with different characteristics of sham-chewing behavior.This experiment is based on the groups of section 1,group H?M and L.After farrowing of the target sows,randomly selects 3 sows in each group and euthanasia in order to dissect hippocampus,prefrontal cortex,hypothalamus and pituitary,observe the microscopical and ultrastructural tissue structures,detect expression levels of IL-6 and BDNF.Compared with group M and L,the results of microscopical observation in group H showed significant reducing the number of neuronal cells,increasing the phenomenon of vacuolization and congestion in some cells in the hippocampus,prefrontal cortex and hypothalamus,also sig nificant reducing in pituitary cells.Compared with group M and L,the results of ultrastructural observation in group H showed mitochondrial sputum rupture and releasing their contents,increasing the number of vacuoles in the cytoplasm in brain tissue.Moreover,group H revealed the phenomenon of nuclear chromatin marginalization in some cells of hippocampus,hypothalamus and pituitary.Molecular level results showed that IL-6 m RNA expression levels in hippocampus,prefrontal cortex,hypothalamus and pituitary tissues were significantly higher in group H than the other two groups(P=0.011;P=0.013;P=0.035;P=0.001).The m RNA expression levels of BDNF in hippocampus and hypothalamus were significantly lower in group H(P<0.01),but not in the pituitary and prefrontal cortex tissues(P>0.05).The results of IL-6 and BDNF m RNA expression levels were basically consistent with their protein expression levels by Western blot analyzing.The expression of IL-6 protein in hippocampus,prefrontal cortex and pituitar y was significantly higher in group H than that in group L(P<0.05),but there was no significant difference in hypothalamus(P>0.05).The expression of BDNF protein in group H was significantly higher in the hippocampus and hypothalamus,while significantly lower in the prefrontal and pituitary than that in group L(P<0.05).Conclusion:The frequency of sham-chewing behavior of pregnant sows is consistent with changes in microscopical and ultrastructural changes in brain tissue,and is associated with increasing expression of IL-6 and decreasing expression of BDNF,possibly reflecting the chronic stress and depressive-like status in sows. |
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