Effects of dietary supplementation of yeast chromium and dihydropyridine on physiological and biochemical indices and HSP70 mRNA expression of periparturient dairy cows under heat stress
In order to investigate the effects of dietary supplementation of yeast chromium and dihy-dropyridine on physiological and biochemical indices and HSP70 mRNA expression of periparturient dairy cows under heat stress,a total of 24 periparturient Holstein-Friesian cows with similar body weights and parity were randomly assigned to three groups.Cows were housed at high ambient temperature-humidity in-dex(above 68)for 40 d,and the effects of yeast chromium and dihydropyridine on the heat stress response of perinatal dairy cows were observed during the experimental period.The control group was fed with basal diet,the chromium yeast group was fed with basal diet plus chromium 1‰ and the amount of chromium yeast was 8 g/d,and the dihydropyridine group was fed with basal diet plus dihydropyridine and the amount of chromium yeast was 3 g/d.The results showed as follows:① Compared with the control group,there was no significant difference in respiratory rate of periparturient dairy cows in chromium yeast group and dihydropyridine group(P>0.05).② Compared with the control group,there was no significant difference in serum blood glucose and cholesterol in yeast chromium group and dihydropyridine group on the 7th day before delivery and the 3rd day after delivery(P>0.05).Compared with the control group,the content of serum triglyceride decreased significantly in dihydropyridine group on the 7th day before delivery(P<0.05).③ Compared with the control group,there was no significant differences in serum Na+,K+ and Cl-concentrations in chromium yeast group and dihydropyridine group before and after delivery(P>0.05),and the concentrations of serum alkaline phosphatase and creatine kinase did not change significantly in the two experimental groups before and after delivery(P>0.05).④ There was no significant difference in the expression of heat shock protein 70 mRNA in serum between chromium yeast group,dihydropyri-dine group and control group(P>0.05).In conclusion,dietary supplementation of 8 g/d yeast chromium with 1‰ chromium and 3 g/d dihydropyridine had no significant effects on physiological and biochemical in-dices and HSP70 mRNA expression of periparturient dairy cows under heat stress.These results indicated that supplementation of 8 g/d yeast chromium with 1‰ chromium and 3 g/d dihydropyridine had no signifi-cant effect on relieving heat stress of perinatal Holstein dairy cows.
heat stressperinatal cowschromium yeastdihydropyridineserum biochemical index
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