| In modern pig production system,confinement such as gestation stalls is a chronic stressor to sows,because space restriction limited expression of innate behaviors of pregnant sows and the sows can not turn around,move and investigate.The previous studies had shown that long-lasting confinement of sows would not only lead to abnormal behavioral responses and physiological reactions,but also negatively influence psychology of sows such as frustration or depression.Therefore,this study aim to evaluated the degree of adverse effects of confinement mode on sow behavioural expression,physiological,PLR responses and hippocampus histomorphology and related hippocampal CA3 and dentate gyrus cell morphology and provide an important scientific basis for improving the welfare of sow production.Section 1: Effects of confinement duration and parity on behavioural responses in pregnant sowsThe aim of this study was to research the effects of space restriction on the behaviour response of pregnant sows during gestation period.We selected 50 pregnant sows(Large White)at primiparity in a confined farm with the same body condition and due date(3±1.5 days).Twelve sows were randomly selected from every parity group and behavioural observations were carried out during the stages of confinement throughout pregnancy.Genenral state behaviors were standing,ventral lying,lateral lying and sitting;genenral event behaviors were vacuum-chewing,bar-biting,trough-biting,rooting,drinking and grooming.The results showed that there were no significant changes in abnormal behavior frequency of primiparous gilts during the initial confinement(1-15 days).With the increase of the confinement duration(from the 25 th day to the 100 th day of gestation),the vacuum-chewing frequencies of sows in all of the experimental groups increased significantly(p <0.01)and the frequencies of the fifth parity sows were significantly higher than those of the other groups(p <0.01)throughout the entire stages of confinement.The rooting frequencies of all the experimental sows decreased continuously,and the young group(primiparity)had a significantly higher rooting frequency than that of the older group(p <0.01)at the 25 th and the 40 th day of gestation.The NOT results showed that the frequencies and the durations of contact with the novel object of the older sows were significantly decreased from the 25 th day to the 85 th day of gestation(p <0.01).The standing,barbiting and trough-biting frequencies of all parity sows were decreased significantly(p <0.01)after entering the farrowing pen.In conclusion,throughout the gestation period,short-term environmental constraints will not cause adaptive changes in sow behaviour,but long-term environmental constraints can significantly increase the frequency of stereotypical behaviour and fear of novel stimuli.Section 2: Effects of confinement duration and parity on physiological and immune responses in pregnant sowsThe aim of this study was to research the effects of space restriction on the physiological and immune response of pregnant sows during gestation period.Eight sows were randomly selected from every parity group and the serum cortisol,Dopamine,Immunoglobulin A,C-Reaction Protein,PigMajor Acute phase Protein,Interleukin-6 and Interferon γ concentrations were analysed by using the method of enzyme-linked immuno sorbent assay.The results showed that the serum CRP and Pig-MAP concentration of primiparous gilts significantly increased during the initial confinement(1-15 days)(p <0.01),while the cortisol concenreation decreased significantly(p <0.01).With the increase of the confinement duration(from the 25 th day to the 100 th day of gestation),the serum cortisol,IgA,IL-6 concentrations of sows in all of the experimental groups increased significantly and the serum concentrations of CRP and Pig-MAP increased significantly except for the sows in the first and second parity group(p <0.01).The serum cortisol,IgA,IL-6 concentrations of older sows were significantly higher than those of the young sows throughout the entire stage of the restricted feeding period(p <0.01),but the concentrations of serum CRP of primiparous gilts were significantly higher than those of the other groups(p <0.01).The serum cortisol,IgA,IL-6 of all parity sows were decreased significantly after entering the delivery bed(p <0.01).In conclusion,short-term environmental confinement would produce acute stress response and increased the sow’s physiological adaptability on the adverse environment,while long-term environmental confinement would make sows’ environmental adaptation very poor and caused seriously physiological stress.Section 3: Effects of confinement duration and parity on pupli light reflex responses in pregnant sowsThe aim of this study was to research the effects of space restriction on the pupli light reflex response of pregnant sows during gestation period.PLR parameters of the sows who had been conducted behavior and blood tests were measured by using NeurOptics PLR‐200 Pupillometer.The results showed that: The latency of pupil constriction onset significantly increased(p<0.01)and the time of 75% recovery after constriction in the primiparous sows significantly decreased(p<0.01)during the initial confinement(1-15 days).The latency of pupil constriction onset increased significantly and the time of 75% recovery after constriction in all of the experimental groups significantly decreased(p <0.01)except for the second and fourth parity group throughout the entire stage of the restricted feeding period;the latency of all parity sows decreased significantly and the time of 75% recovery after constriction increased significantly after entering the delivery bed(p <0.01).The time of 75% recovery after constriction in the fifth parity sows significantly increased,while those of the latency significantly decreased(p <0.01).The latency of the pupil constriction onset was significantly positively correlated with the frequency of vacuum-chewing throughout pregnancy(p <0.01),while the time of 75% recovery after constriction was significantly positively correlated with the serum concentrations of cortisol in the mid-late stage of pregnancy(p <0.01).In conclusion,long-term environmental confinement significantly increased the latency of the pupil light reflex and significantly decreased the total time taken by the pupil to recover 75% of the inital resting pupil size after it reached the peak of constriction and there was a relationship between the psychological state of stress caused by space restriction and the latency and 75% recovery time of the PLR.Section 4: Effects of confinement duration and parity on psychological responses in pregnant sowsThe aim of this study was to research the effects of space restriction on psychological of pregnant sows during gestation period.We selected 40 Large White sows that had experienced restricting for about 0.5 or 3 years and age-matched sows kept in a group housing system(loose sows)were compared.After weaning,five sows with no obvious trauma were randomly selected from each experimental group for blood collection,the serum BDNF was measured and the sows were mercy killing immediately and decollation.The technology of magnetic resonance imaging(MRI)was applied to analyze hippocamal morphological changes.Microscopic observation of CA3 and dentate gyrus(DG)cell morphology and organelle integrity was completed by using the method of optical and electron microscopy.The results showed that,the older,but not the younger,serum BDNF levels were significantly lower in the confined sows than in the loose sows(p <0.01).MRI analyses revealed that a significant volume decreased in the both left and right hippocampus of the older confined sows compared with the loose sows(p <0.01).Optical microscopy observation showed that: Compared with the loose reared sows,a large number of CA3-region pyramidal cells and and DG-region granule cells of the confined sows decreased,and arranged irregularly,forming a large number of vacuoles.TEM observation showed that: CA3 and DG region cells’ nuclear membranes were irregular,and accompanied by mitochondria swelling and a large number of cristae ruptured and disappeared in the sows reared in the confined farm.In conclusion,long-lasting space-restricting stress would produce depression-like effects in the brain regions associated with emotions and physiological response. |
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