Weber C, Losand B, Tuchscherer A, Rehbock F, Blum E, Yang W, Bruckmaier R M, Sanftleben P, Hammon H M
Institute of Nutritional Physiology "Oskar Kellner," Leibniz Institute for Farm Animal Biology (FBN), 18196 Dummerstorf, Germany.
State Institute of Animal Production, 18196 Dummerstorf, Germany.
J Dairy Sci. 2015 Mar;98(3):1772-85. doi: 10.3168/jds.2014-8598. Epub 2014 Dec 26.
Dry period (DP) length affects energy metabolism around calving in dairy cows as well as milk production in the subsequent lactation. The aim of the study was to investigate milk production, body condition, metabolic adaptation, and hepatic gene expression of gluconeogenic enzymes in Holstein cows (>10,000 kg milk/305 d) with 28- (n=18), 56- (n=18), and 90-d DP (n=22) length (treatment groups) in a commercial farm. Cows were fed total mixed rations ad libitum adjusted for far-off (not for 28-d DP) and close-up DP and lactation. Milk yield was recorded daily and body condition score (BCS), back fat thickness (BFT), and body weight (BW) were determined at dry off, 1 wk before expected and after calving, and on wk 2, 4, and 8 postpartum (pp). Blood samples were taken on d -56, -28, -7, 1, 7, 14, 28, and 56 relative to calving to measure plasma concentrations of metabolites and hormones. Liver biopsies (n=11 per treatment) were taken on d -10 and 10 relative to calving to determine glycogen and total liver fat concentration (LFC) and to quantify mRNA levels of pyruvate carboxylase (PC), cytosolic phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase. Time course of milk yield during first 8 wk in lactation differed among treatment. Milk protein content was higher in 28-d than in 90-d DP cows. Milk fat to protein ratio was highest and milk urea was lowest in 90-d DP cows. Differences in BW, BFT, and BCS were predominantly seen before calving with greatest BW, BFT, and BCS in 90-d DP cows. Plasma concentrations of NEFA and BHBA were elevated during the transition period in all cows, and the greatest increase pp was seen in 90-d DP cows. Plasma glucose concentration decreased around calving and was greater in 28-d than in 90-d DP cows. Dry period length also affected plasma concentrations of urea, cholesterol, aspartate transaminase, and glutamate dehydrogenase. Plasma insulin concentration decreased around calving in all cows, but insulin concentration pp was greater in 28-d than in 56-d DP cows. Hepatic glycogen concentration decreased and LFC increased after calving in all cows, and LFC was greater pp in 90-d DP than in 28-d DP cows. Hepatic PC mRNA abundance pp tended to increase most in 90-d DP cows. Changes on glucose metabolism were more balanced in cows with a reduced DP, whereas cows with extended DP and elevated body condition indicated greatest metabolic changes according to lipid and glucose metabolism during the transition period.
干奶期（DP）的长短会影响奶牛产犊前后的能量代谢以及随后泌乳期的产奶量。本研究的目的是调查商业农场中干奶期长度分别为28天（n = 18）、56天（n = 18）和90天（n = 22）（处理组）的荷斯坦奶牛（305天产奶量>10,000千克）的产奶量、体况、代谢适应性以及糖异生酶的肝脏基因表达。奶牛自由采食全混合日粮，日粮根据干奶前期（不适用于28天干奶期）、围产前期和泌乳期进行调整。每天记录产奶量，并在干奶时、预计产犊前1周、产犊后以及产后第2、4和8周测定体况评分（BCS）、背膘厚度（BFT）和体重（BW）。在相对于产犊的第 -56、-28、-7、1、7、14、28和56天采集血样，以测量血浆中代谢物和激素的浓度。在相对于产犊的第 -10天和第10天进行肝脏活检（每个处理11头），以确定肝糖原和肝脏总脂肪浓度（LFC）并定量丙酮酸羧化酶（PC）、胞质磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸酶的mRNA水平。泌乳期前8周的产奶量时间进程在各处理组间存在差异。28天干奶期的奶牛乳蛋白含量高于90天干奶期的奶牛。90天干奶期的奶牛乳脂与蛋白比例最高，乳尿素最低。BW、BFT和BCS的差异主要出现在产犊前，90天干奶期的奶牛BW、BFT和BCS最大。所有奶牛在过渡期血浆非酯化脂肪酸（NEFA）和β-羟丁酸（BHBA）浓度均升高，90天干奶期的奶牛产后增加幅度最大。产犊前后血浆葡萄糖浓度降低，28天干奶期的奶牛血浆葡萄糖浓度高于90天干奶期的奶牛。干奶期长度还影响血浆尿素、胆固醇、天冬氨酸转氨酶和谷氨酸脱氢酶的浓度。所有奶牛产犊前后血浆胰岛素浓度均降低，但产后胰岛素浓度28天干奶期的奶牛高于56天干奶期的奶牛。所有奶牛产犊后肝糖原浓度降低，LFC升高，90天干奶期的奶牛产后LFC高于28天干奶期的奶牛。产后90天干奶期的奶牛肝脏PC mRNA丰度增加趋势最为明显。干奶期缩短的奶牛葡萄糖代谢变化更为平衡，而干奶期延长且体况升高的奶牛在过渡期根据脂质和葡萄糖代谢显示出最大的代谢变化。
