饲粮硒含量对酮病奶牛氧化应激的缓解作用

Mitigative Effect of Dietary Selenium Content on Oxidative Stress of Ketotic Dairy Cows

本试验旨在通过研究饲粮硒含量对酮病奶牛氧化应激的缓解作用,并确定酮病奶牛对硒的最适需求量。采用完全随机区组设计,将40头胎次为(3.43±0.87)胎、泌乳天数为(6.33±1.14)d、体重为(644±36)kg、平均泌乳量为(38.42±4.82)kg/d、血浆β-羟丁酸(BHBA)水平为(1.50±0.26)mmol/L的荷斯坦奶牛随机分成4组,每组10头牛。第1组为对照组,饲喂基础饲粮(硒含量为0.15 mg/kg DM);第2、3、4组为试验组,在基础饲粮中加入亚硒酸钠(Na2Se O3)至饲粮硒含量分别达到0.30(试验组1)、0.45(试验组2)和0.60 mg/kg DM(试验组3)。试验分为3期,每期1周。试验每期结束后采集血样,并在第2期结束后每组随机选取5头牛采集肝组织。结果表明:1)试验组酮病奶牛全血、肝脏中硒含量,肝脏中总抗氧化能力(T-AOC)、超氧化物歧化酶(SOD)活性和谷胱甘肽过氧化物酶(GPx)活性以及GPx1与GPx4mRNA的相对表达水平均显著高于对照组(P<0.05),同时试验组2和3还显著高于试验组1(P<0.05)。2)试验组酮病奶牛肝脏中丙二醛(MDA)和过氧化氢(H2O2)含量均显著低于对照组(P<0.05),同时试验组2和3还显著低于试验组1(P<0.05)。3)试验组酮病奶牛血浆非酯化脂肪酸(NEFA)水平显著低于对照组(P<0.05),但血浆葡萄糖和BHBA水平与对照组相比无显著差异(P>0.05)。4)饲粮硒含量为0.45和0.60 mg/kg DM时,酮病奶牛全血和肝脏中硒含量、肝脏抗氧化指标和血浆能量代谢指标均无显著差异(P>0.05)。由此得出,饲粮硒含量为0.45 mg/kg DM时可显著改善酮病奶牛机体的抗氧化能力。

The present study was aimed to evaluate the mitigative effect of dietary selenium（Se） content on oxidative stress of ketotic dairy cows,and to confirm the Se requirement of ketotic dairy cows.Forty Holstein dairy cows with（3.43±0.87） parities,（6.33±1.14） days in lactation,body weight of（644±36） kg,average milk yield of（38.42±4.82） kg/d and plasma β-hydroxybutyrate（BHBA） level of（1.50±0.26） mmol/L were assigned to 4 groups（n= 10） according to a completely randomized design.The 1st group was control group,and the dairy cows in this group were fed a basal diet（Se content was 0.15 mg/kg DM）;the 2nd,3rd and 4th group were test groups,and the dairy cows in those groups were fed the basal diet added with sodium selenite（Na_2SeO_3） until the Se content was 0.30（test group 1）,0.45（test group 2） and 0.60 mg/kg DM（test group 3）,respectively.The experiment period was divided into three periods and each period had 7 days.The blood samples were collected from all cows on the last day of each period,and the hepatic tissues were collected from five cows randomly selected from each group on the last day of the 2nd period.The results showed as follows：1） the Se content in whole blood and liver,the total antioxidant capacity（T-AOC）,superoxide dismutase（SOD） activity,glutathione peroxidase（GPx） activity and the relative expression levels of GPx1 and GPx4 mRNA in liver of ketotic dairy cows in test groups were significantly higher than those in control group（P〈0.05）;meanwhile,those indexes in test groups 2 and 3 were significantly higher than those in test group 1（P〈0.05）.2） The malondialdehyde（MDA） and hydrogen peroxide（H_2O_2） contents in liver of ketotic dairy cows in test groups were significantly lower than those in control group（P〈0.05）;meanwhile,those indexes in test groups 2 and 3 were significantly lower than those in test group 1（P〉0.05）.3） No significant differences were found in plasma glucose and BHBA levels between test groups and control group（P〈0.05）,but the plasma not fat fatty acids（NEFA） level in test groups was significantly lower than that in control group（P〉0.05）.4） There were no significant difference in the Se content in whole blood and liver,liver antioxidant indexes and plasma energy metabolism indicators of ketotic dairy cows when dietary Se contents were 0.45 and 0.60 mg/kg DM（P〈0.05）.In conclusion,diet containing 0.45 mg/kg DM Se can significantly improve the anti-oxidation ability of ketotic dairy cows.