The Effects And Mechanism Of Antioxidants On Performance And Antioxidant Capacity And Immunity Ofcows In Heat Stress

Heat stress is an important factor that influences the milk production and quality.The research found that oxidative stress plays a key role in resulting in mammary gland cells damage and functional disorder.Our study is aiming to optimize the extraction technology for total antioxidant capacity from the stem and leaf of Orthosiphon aristatus,establish HC11 cells oxidative stress model induced by H₂O₂,and study the effects and mechanisms of antioxidant on the HC11 cells repair under oxidative stress,studied the effects of antioxidant on performance and antioxidant capacity and immunity of dairy cows in heat stress.In the first part,response surface method was used to study the effects of extration temperature,extraction ethanol concentration,extration time and liquid-solid ratio on extract antioxidant capacity extract.Results showed that the valuable extraction condition of stem and leaf is extration temperature 70?,extraction ethanol concentration 56.25%,extration time 25.59 min,liquid-solidratio 1:40 and extration temperature 69.93?,extraction ethanol concentration 55.85%,extration time 24.36min,liquid-solidratio 1:40.On the condition,the result showed the practical total antioxidant capacity from stem and leaf of Orthosiphon aristatus extracts are respectively equivalent to 211.41 mmol and 919.25 mmol Trolox,and theactual total antioxidant capacity from stem and leaf of Orthosiphon aristatus extracts are respectively equivalent to 209.96 mmol and 915.86 mmol Trolox.The second part is to establish HC11 cells oxdative stress model induced by H₂O₂ and study the effects of three antioxidants on the HC11cells repair by H₂O₂-induced oxdative stress model.The results showed that the optimal concentration and time of H₂O₂ for oxidative stress model is 400?mol/L and 3 h.The micro-derived antioxidant,extract of Orthosiphon aristatus stem and leaf can repair the cells activity in the concentration of 100,10,100?g/L at the greatest extent.In the three experimental groups of antioxidants,the concentration SOD,GSH-Px in HC11 were significantly higher than that of control group?P<0.05?;MDA and protein hydroxylation concentration of three experimental groups were significantly lower than the control group?P<0.05?;DNA damage of the control group is more serious than the experimental group;the caspase concentration were significantly lower than the control group?P<0.05?;the experimental group,the concentration of total protein and?-casein in cells increased significantly?P<0.05?.The third part aimed to study the effects of season on antioxidant capacity of dairy cow,and the effects of micro-derived antioxidants on the performance,antioxidant capacity and physiological indexes of dairy cow in summer.The first test choosed six dairy cow with similar age,parity,lactation period and production performance,and compared the antioxidant capacity of different season on dairy cow.The second test choose thirty-six healthy Holstein cows with the similar age,fetaltime,lactation period and production performance were divided into 2 groups.Control group received a basal diet,and in the experimental group every cow received a basal diet with 50g of micro-derived antioxidants per day.The experiment lasted 60 days in the hot summer.The results showed that,compared with the control group,the milk production of experimental group significantly increased?P<0.05?;however,somatic cell count decreased significantly?P<0.05?.In milk,IHR and the concentration of SOD,GSH-Px,IgA,IgG,IL-2 of the experimental group were significantly higher than the control group?P<0.05?.The MDA and 8-iso-PGF2?concentration in serum and whey of the experimental group were lower than that of the control group?P<0.05?.The experiment indicated that micro-derived antioxidants can enhance the antioxidant capacity,immune-competence and improve the production and quality of milk.The studies suggest that oxdative stress can lead to DNA damage and lipid peroxidation and cell protein carbonylation of HC11 cells,and result in apoptosis of HC11 and reduction of milk protein synthesis.The antioxidant can regulate the process and enhance the antioxidant capacity,immune-competence,and improve the yield and quality of milk in heat stress,the tests confirm heat stress is associated with oxdative stress,we can regulate the antioxidant balance to reduce heat stress effect of dairy cows.