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Abstract：
This study investigated the effects of rumen bypass dandelion extract on the lactation performance, immune index, and mammary oxidative stress of lactating dairy cows fed a high-concentrate diet. This study used a complete randomized block design, and initial milk production, somatic cell counts, and parities were set as block factors. Sixty Holstein cows with similar health conditions and lactating periods (70 ± 15 d) were divided into three groups with 20 replicates per group. The treatments included the LCD group (low-concentrate diet, concentrate-forage = 4:6), HCD group (high-concentrate group, concentrate-forage = 6:4), and DAE group (dandelion aqueous extract group, HCD group with 0.5% DAE). The experimental period was 35 d, and cows were fed three times in the morning, afternoon, and night with free access to water. The results showed the following: (1) Milk production in the HCD and DAE groups was significantly higher (p < 0.05) than that in the LCD group from WK4, and the milk quality differed during the experimental period. (2) The HCD group\'s pH values significantly differed (p < 0.01) from those of the LCD and DAE groups. (3) In WK2 and WK4 of the experimental period, the somatic cell counts of dairy cows in the HCD group were significantly higher (p < 0.05) than those in the DAE group. (4) The serum concentrations of 8-hydroxy-2\'-deoxyguanosine (8-OHdG) and protein carbonyl (PC) in the HCD group were significantly higher (p < 0.05) than those in the LCD group. The activity of catalase (CAT) in the LCD and DAE groups was stronger (p < 0.01) than that in the HCD group. (5) The correlation analysis revealed significantly positive correlations between the plasma LPS concentration and serum concentrations of 8-OHdG (p < 0.01), PC (p < 0.01), and malondialdehyde (MDA, p < 0.05) and significantly negative correlations (p < 0.01) between the plasma LPS concentration and activities of CAT and superoxide dismutase. (6) Compared with that in the HCD and DAE groups, the mRNA expression of α, β, and κ casein and acetyl CoA carboxylase in bovine mammary epithelial cells was significantly higher (p < 0.05) in the LCD group, and the mRNA expression of fatty acid synthetase and stearoyl CoA desaturase in the LCD group was significantly higher (p < 0.01) than that in the HCD group. (7) Compared with that in the LCD and HCD groups, the mRNA expression of Nrf2 was significantly higher (p < 0.01) in the DAE group, and the mRNA expression of cystine/glutamate transporter and NAD (P) H quinone oxidoreductase 1 in the DAE group was significantly higher (p < 0.05) than that in the HCD group. Overall, feeding a high-concentrate diet could increase the milk yield of dairy cows, but the milk quality, rumen homeostasis, and antioxidative capability were adversely affected. The supplementation of DAE in a high-concentrate diet enhanced antioxidative capability by activating the Nrf2 regulatory factor and improved rumen homeostasis and production performance.
摘要：
本研究研究了蒲公英提取物对泌乳性能的影响，免疫指数,和高浓缩日粮喂养的泌乳奶牛的乳腺氧化应激。本研究采用完全随机区组设计，和最初的牛奶生产，体细胞计数,并将奇偶校验设置为阻滞因子。将60头健康状况和泌乳期（70±15d）相似的荷斯坦奶牛分为3组，每组重复20只。治疗方法包括LCD组（低精饮食，集中饲料=4:6)，HCD组（高浓缩组，集中饲料=6:4)，和DAE组(蒲公英水提取物组，含0.5%DAE的HCD组)。实验时间为35d,早上喂奶牛三次，下午,晚上免费取水。结果表明：（1）从WK4开始，HCD和DAE组的牛奶产量明显高于LCD组（p<0.05），并且在实验期间牛奶质量存在差异。（2）HCD组的pH值与LCD和DAE组的pH值显着差异（p<0.01）。(3)在实验期的WK2和WK4,HCD组奶牛体细胞计数明显高于DAE组(p<0.05)。（4）HCD组血清中8-羟基-2'-脱氧鸟苷（8-OHdG）和蛋白羰基（PC）的浓度明显高于LCD组（p<0.05）。LCD和DAE组的过氧化氢酶（CAT）活性强于HCD组（p<0.01）。(5)相关分析显示血浆LPS浓度与血清8-OHdG浓度呈显著正相关(p<0.01),PC（p<0.01），和丙二醛(MDA，p<0.05），血浆LPS浓度与CAT和超氧化物歧化酶活性之间呈显着负相关（p<0.01）。（6）与HCD和DAE组相比，α的mRNA表达，β,和κ酪蛋白和乙酰辅酶A羧化酶在奶牛乳腺上皮细胞中显著高于LCD组(p<0.05),LCD组脂肪酸合成酶和硬脂酰CoA去饱和酶的mRNA表达明显高于HCD组（p<0.01）。（7）与LCD和HCD组相比，DAE组Nrf2mRNA表达明显增高(p<0.01),DAE组的胱氨酸/谷氨酸转运体和NAD（P）H醌氧化还原酶1的mRNA表达明显高于HCD组（p<0.05）。总的来说,饲喂高浓缩饮食可以提高奶牛的产奶量，但是牛奶的质量，瘤胃稳态,和抗氧化能力受到不利影响。在高浓缩饮食中补充DAE通过激活Nrf2调节因子来增强抗氧化能力，并改善瘤胃稳态和生产性能。
