The Effects And Mechanism Of Dietary Diludin On Anti-Heat Stress Capacity In Dairy Cows

This paper studies the effects of dietary diludin on the expression of Heat shock protein gene(Hsp70mRNA, Hsp90mRNA),related gene for apoptosis of lymphocyte(Bcl-2mRNA, BaxmRNA), blood lymphocyte apoptosis rate,anti-oxidized capacity and anti-heat stress capacity of dairy cows. The result showed that diludin could improve the expression of Hsp70mRNA,Hsp90mRNA and Bcl-2mRNA/BaxmRNA,reduce the rate of blood lymphocyte apoptosis. By this way, they may improve the antioxidant capacity and health condition of dairy cows.The experiment I was conducted with 40 Holstein cows in midlactation. According to the decrease rate of milk yield,these cows were divided into high-yield group and low-yield group, the decrease rate of milk yield lower than 30% named as high-yield group, higher than 50% named as low-yield group. The relationship between the antioxidant indexes and milk yield was analyzed,the results indicated that the activities of SCD、GSH-Px and T-AOC in serum were negatively correlated with the decrease rate of milk yield (r=-0.462,P<0.01),(r=-0.291,P>0.05)and(r= 0.515,P<0.01);The content of MDA in serum was positively correlated with the decrease rate of milk yield(r=0.371,P<0.05). the expression of Hsp70mRNA,Hsp90mRNA and Bcl-2mRNA/BaxmRNA were negatively correlated with the decrease rate of milk yield (r=-0.619,P<0.01),(r=-0.515,P<0.01)and (r=-0.669,p<0.01). Results also showed that, the reason of milk yield decrease in summer maybe correlared with blood lymphocyte apoptosis and decrease of animal body’s antioxidant enzyme activity.The experiment II was used 16 Holstein cows in midlactation were assigned randomly into diludin group (n=8)and non-diludin group(n=8), two experimental period were conducted, optimum-temperature period(2010.4. spring) and high-temperature period(2010.7.1—2010.8.15.summer).The average THI were above 72 in the 2nd period. The changes of antioxidant indexes in serum and whey of different experimental groups during two experimental period were analyzed, the results indicated that,the activities of SOD,GSH-Px,CAT and T-AOC in serum and whey reduced in high-temperature period, accompany with the increase content of MDA was increased. The values of SOD、GSH-Px、CAT and T-AOC of the diludin group significantly higher than the non-diludin group in high-temperature period (P<0.05). The relative expression of Hsp70mRNA, Hsp90mRNA, Bcl-2mRNA, and BaxmRNA were analysed by relative quantitative RT-PCR.The expression of Hsp70mRNA and Hsp90mRNA were extremely increased in the high-temperature period, and the level of the expression of Hsp90mRNA of the diludin group higher than the non-diludin group atl5d and 30din high-temperature period (P<0.05).The ratio of Bcl-2mRNA/BaxmRNA of the diludin group was significantly higher than the non-diludin group at 30d and 45d (P<0.05).It is concluded that, the heat stress decreased the antioxidant capacity and increased the ratio of Bcl-2mRNA/BaxmRNA,which could cause the cell apoptosis.The supplementation of diludin maybe have the ability to improve the antioxidant activity and the abundance of HSPs mRNA to reduce the rate of blood lymphocyte apoptosis of dairy cows.