| Self-biting behavior was unconscious self-injurious behavior in mink,but little was known about the biological basis of this disorder. All minks in this study were young mink weaned present year in Jinzhou mink farm in Dalian. The subject of this research was to compare the behavior of self-biting mink and health mink, to test anti-oxidative enzyme activity, methyl mercury (MeHg) and total mercury (THg) , to determine the effect of Ca2+ channel inhibitor on self-biting behavior, to research on the effect of VE+Na2SeO3 on self-biting behavior and oxidative enzyme activity. The nervous system pathological changes in mink with self-injurious behavior also were investigated in this study. The research result saw as below:1 Rules of self-biting behavior and the effect of management stress on behavior in farmed mink.60 self-biting minks and 60 clinical health minks (half male and half female) were choose from weaned mink in current year, each group 20 minks(half male and half female); investigated the self-biting behavior regular. Moved mink house, and caught and injected within 3 day to research the effect of managing stress on self-biting frequency and stereotypical behavior in mink. The result shown that self-biting behavior was intermittent occurrences; self-biting time was centered in night and the time before feeding. July and September is the peak of self-biting behavior, and self-biting frequency also reached the peak data. Both self-biting group and clinical health group have stereotypical behavior. The rate of incidence of stereotypical behavior was 19.44% and 11.67% respectively. Moved mink house, and catching and injecting within 3 day increased the self-biting frequency significantly, but it shown the down trend in next 6 and 9 day. This managing stress also increased stereotypical behavior rate in health and self-biting mink, it has same trend with self-biting frequency. Self-biting behavior is intermittent occurrence neurologic behavioral disease; stereotypical behavior happened both in self-biting mink and health mink. Moving house, catching and injecting stimulated the incidence of self-biting and stereotypical behavior.2 Anti-oxidative system and correlation with Hg residue of self-biting mink10 male and female minks were selected randomly from self-biting and health mink respectively, taken blood by cardiac puncture, to test hematological and biochemical Indexes of self-biting and health mink. 20 health and self-biting minks were selected randomly, heart-air-injection to death and take liver, kidney, brain and muscle samples to test the anti-oxidative enzyme activity, THg and MeHg. The results shown that, RBC, Hgb, MCV, MCH and BPC had no difference between self-biting mink and health mink. But WBC of self-biting mink was higher significantly than health mink(p<0.01). GSH level in self-biting mink was lower than health mink( p<0.01). The content of GSH was only 76% compare with normal mink. VE level in liver and brain of self-biting mink also was 22.5% and 21.1% lower than health mink. SBB minks had higher total superoxide dismutase (SOD), Cu/Zn-SOD and Mn-SOD activities in both tissues (p <0.05 or p <0.01). Catalase (CAT) activities in liver and brain tissues of SBB minks were markedly lower than those of normal group (p <0.01). GPx activities also lower than normal mink, but only have significant different in brain. SBB minks produced more MDA with 51% increase in brain (p <0.01) and 22% increase in liver (p <0.01) compared to normal minks. Similarly, the hepatic and cerebral PC in SBB minks were 18.5% (p <0.01) and 30% higher (p<0.001), respectively. Ca2+-ATPase and NOS activities in the brain of SBB minks were lower than health mink (p <0.01). SIB minks accumulated more cerebral MeHg and hepatic THg compared to the normal minks (p <0.05 or p <0.01) with 48.8% increase in brain and 20% increase in liver of MeHg, 16% increase in liver and 44.8% increase in brain of THg. But there were no significant differences in kidney between the two groups. The correlation between MeHg or THg accumulation and GSH or MDA levels in SIB group was not consistent with that in normal group. In normal group, only cerebral GSH had negatively correlation with MeHg or THg concentrations. While in SIB group, both cerebral and hepatic GSH level had negative effect on MeHg accumulation, and a significantly positive correlation between MDA and MeHg or THg was found in all of the three tissues.3 The effect of VE+Na2SeO3 and Nimodipine on self-biting behavior in mink72 standard color minks with self-biting behavior were selected, half male and half female, divide into 3 group, 3 repeats in each group and 8 self-biting minks in each repeat. 3 treatments were control, Nimodipine and Nimodipine+VE+Na2SeO3 respectively. In Nimodipine group, 25ppm nimodipine was add in mink feed. The feed supply was 200g each mink each day. Nimodipine intake was 5mg each mink each day. 50ppm VE, 5ppm Na2SeO3 and 25ppm nimodipine was added in mink feed in Nimodipine+VE+Na2SeO3 group. The study of this research was to determine the effect of Ca2+ channel inhibitor and Vitamin E and Na2SeO3 on the self-biting behavior. The result shown that, self-biting frequency decreased remarkable in the beginning, but this effect reduced day by day after 12 d in Nimodipine group, the self-biting frequency increased again. But the self-biting frequency lower than control group in experiment period. Nimodipine+VE+Na2SeO3 decreased self-biting frequency significantly after 9 d of treatment, this effect continued in all experiment period.4 The effect of VE+Na2SeO3 on accidence rate of self-biting and anti-oxidative enzyme activity and Hg residue in mink.1920 weaned minks were selected randomly and divided into 2 groups, each group has 4 repeats, 240 minks in each repeats. 50ppm VE and Na2SeO3 add in feed of treatment group to research the effect on accident rate of self-biting. Selected 32 minks in every group before take fur in winter, heart-air-injection to death and taken liver, kidney and brain samples to test GSH, VE level, anti-oxidative enzyme activity and MeHg residue in tissues. Experiment result shown that, VE+Na2SeO3 group decreased the self-biting accident rate of mink significantly(p<0.01). VE level increased in liver in treatment group(p<0.01), GSH level in liver and brain also higher than control group(p<0.05). VE +Na2SeO3 improved GPx activities in brain and liver(p<0.01), and CAT in liver also increased in treatment group(p<0.01), but have no effect on CAT activity in brain tissue. CuZn-SOD activities in liver and brain were lower than control group( p<0.05 or 0.01),but no effect on T-SOD,Mn-SOD. VE+Na2SeO3 decreased MeHg level in brain and liver significantly (p<0.05), but have no effect on HeHg level in kidney. VE+Na2SeO3 treatment decreased MDA level in liver and brain significantly (p<0.01).5 Histopathological studies on nervous system in self-biting behavior minkThe cerebrum, cerebellum, medulla oblongata and medulla marrow from each of 20 healthy minks and 20 self-injurious minks were collected in current study. All samples were fixed in 4% paraformaldehyde, followed by dewatering, hyalining, paraffin embedding, slicing and hematoxylin eosin staining. All sections were observed at 200- 400 times light microscope. Compared with clinical health mink, histopathological changes were found in nervous system of minks with self-injurious behavior. Swelling, lysing and microsatellite phenomenon of nerve cells were observed in the cerebrum. Many nuclei in nerve cells became pyknotic (shrunken and dark). Vacuolizations were observed in cerebrum of some minks with self-injurious behavior. Intracellular membrane of neuroglia cell was deeply stained. Swollen and lysed Purkinje cells were investigated in cerebellum, and some of the myelin sheaths were lysed in this region. Neurocyte swelling, membrane ablation of macroglia and serious microsatellite phenomenon were observed in medulla oblongata of SIB mink. Nerve cells pyknotic and membrane lysed also found in spinal marrow. Self-injurious behavior of minks has correlation with pathological changes of membrane of nerve cell and nerve myelin sheath.
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