PSXVII-30 Effects of dietary supplementation of yeast chromium and dihydropyridine on serum biochemical indices and HSP70 mRNA expression of lactating dairy cows in summer.

摘要

The objective of this study is to evaluate the effects of dietary supplementation of dihydropyridine and yeast chromium on serum biochemical indices and heat stress protein (HSP) concentration of lactating Holstein dairy cows in summer. Twenty-four lactating cows were assigned to three treatments: control, yeast-chromium supplementation (Cr-Yeast, 8 mg/d) and dihydropyridine supplementation (Dih, 3.0 g/d). The trial was conducted during summer and included a 6 d adaption period, followed by a 46 d experimental period for samples and data collection. The temperature humidity index (THI) was daily recorded at 10:00, 12:00 and 15:00. Blood samples were collected from coccygeal vessels on d 29 (15:00) and d 44 (15:00), part of which were immediately centrifuged to collect the serum. Automatic electrochemical luminescence analyzer was used to measure the serum triiodothyronine and tetraiodothyronine concentration using the direct luminescence competition method, while serum concentration of alkaline phosphatase and creatine kinase (CK) was determined by using IFCC reference method. RNA was extracted from the red blood cells and qPCR was used for testing the HSP70 mRNA expression in blood. The average temperature-humidity indexes at 10:00, 12:00 and 15:00 were 81.4, 83.0 and 83.8, respectively, which indicated the moderate heat stress during experiment. Supplementation of dihydropyridine significantly decreased the serum concentration of CK on d 29 ( < 0.05), while feeding dihydropyridine or yeast chromium decreased serum concentration of CK significantly on d 44 ( < 0.05). Treatments had no effects on blood HSP mRNA expression on d 29 ( > 0.05), while blood HSP mRNA expression on d 44 was significantly improved by the supplementation of chromium yeast ( < 0.05). In conclusion, supplementing yeast chromium and dihydropyridine decreased serum concentration of CK and improved antioxidant status in lactating dairy cows in summer.