| This paper studied the effects of melatonin on the physiological and biochemical indexes and the expression of Mac-T cells inflammatory factors in heat-stressed Holstein cattle.It provides a theoretical basis for clinically melatonin to prevent dairy cow mastitis and relieve heat stress of dairy cows.Experiment 1,according to the principle of similar age and weight,25 healthy Holstein cows with a weight increase(317±15 kg)at the age of 14 months were selected in the experiment,and randomly divided into A、B、C,、D、E five test groups,five cows per group,12 days of formal trial,Group A was injected with 10ml of normal saline subcutaneously every day from 1st to 6th days,Group B was injected with 10ml 0.46mg/ml Melatonin preparation subcutaneously every day from 1st to 6th days,Group C was injected with 10ml 4.6mg/ml Melatonin preparation subcutaneously every day from 1st to 6th days,Group D was injected with 10ml 0.46mg/ml Melatonin sustained-release agents preparation subcutaneously every day from 1st to 6th days,Group E was injected with 10ml 4.6mg/ml Melatonin sustained-release agents preparation subcutaneously every day from 1st to 6th days,to study the effect of melatonin on the physiological and biochemical indexes of heat-stressed Holstein dairy cows.the results show:(1)During the experiment,the average THI of the barn was 85.56,indicating that the cow was in a state of moderate heat stress.(2)Melatonin and melatonin sustained-release agents have no effect on the number of exercise steps and rectal temperature of heat-stressed cows.It can reduce the breathing rate of heat-stressed cows.(3)Melatonin and melatonin sustained-release agents can significantly increase the levels of T3 and COR hormones in the serum of dairy cows(P<0.05),and increase the level of T4 hormones.(4)Melatonin and melatonin sustained-release agents can significantly increase the level of Glu in dairy cow serum(P<0.05),reduce the content of TC,and have no effect on the content of TP,ALB,CK and LDH.(5)Melatonin and melatonin sustained-release agents can significantly increase the activity of serum CAT and GSP-Px enzymes in dairy cows(P<0.05),have no effect on the activity of SOD enzymes,significantly reduce the content of MDA(P<0.05),and increase heat The total antioxidant capacity of stressed Holstein cow serum.(6)Melatonin and melatonin sustained-release agents can significantly reduce the Hsp70 content in the serum of heat-stressed dairy cows(P<0.05).Experiment 2,Collect Mac-T cells in the logarithmic growth phase,and count them with a cell counter,inoculate the Mac-T cells suspension on the 12-well plate,2ml per well,and the number of cells was 2.5×105,divided into control group,heat stress group,heat stress+MLT group,3 repetitions per group.The control group,heat stress group,and heat stress+MLT group were put into two CO2 incubators respectively,each group was first cultured in a 37℃ 5%CO2 incubator for 24h;Replace with new culture medium,The control group was cultured with 100μl DMEM for 16h.Heat stress group plus 100μl DMEM,heat stress+MLT group plus 100μl MLT reagent to make the final concentration of MLT 150μMol/L,continue to culture for 12h,adjust the temperature of the incubator in the heat stress group and heat stress+MLT group to 42℃,continue to incubate for 4 hours,establish a heat stress cell model,to study the effect of melatonin on the expression of inflammatory factors in Mac-T cells,the results show:(1)There was no significant difference in the proliferation activity of Mac-T cells in each group under heat stress for 2 hours(P>0.05);The proliferation activity of Mac-T cells was significantly reduced for 4 hours of heat stress(P<0.05),the addition of 150μMol/L MLT could significantly increase the proliferation activity of Mac-T cells(P<0.05);At 6 hours of heat stress,the proliferation activity of Mac-T cells in heat stress group and heat stress+MLT group was significantly lower than that in control group(P<0.05).(2)Heat stress can significantly up-regulate the expression of Mac-T cells apoptosis factor Caspase-3,inflammatory factors IL-6,IL-8 and heat shock protein Hsp70(P<0.05),the addition of 150μMol/L melatonin can significantly down-regulate the expression of Mac-T apoptosis factor Caspase-3,inflammatory factors IL-6,IL-8 and heat shock protein Hsp70(P<0.05).In conclusion:(1)Subcutaneous injection of melatonin can improve the heat stress response by adjusting the physiological and biochemical indicators of dairy cows,relieve heat stress in dairy cows.(2)Heat stress can significantly reduce the proliferation of Mac-T cells,and significantly increase the expression of inflammatory factors IL-6,IL-8,apoptosis factor Caspase-3,and heat shock protein Hsp70;The addition of 150μMol/L melatonin can significantly increase the proliferation activity of Mac-T cells,significantly down-regulate the expression of heat stress-induced Mac-T cells inflammatory factors IL-6,IL-8,apoptosis factor Caspase-3,and heat shock protein Hsp70,improve the stress tolerance of Mac-T cells,reduce inflammatory damage and apoptosis. |
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