van Dorland H A, Graber M, Kohler S, Steiner A, Bruckmaier R M
Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland; School of Agricultural, Forest and Food Science, Bern University of Applied Sciences, Zollikofen, Switzerland.
J Anim Physiol Anim Nutr (Berl). 2014 Aug;98(4):693-703. doi: 10.1111/jpn.12125. Epub 2013 Sep 3.
The aim was to study the variation in metabolic responses in early-lactating dairy cows (n = 232) on-farm that were pre-selected for a high milk fat content (>45 g/l) and a high fat/protein ratio in milk (>1.5) in their previous lactation. Blood was assayed for concentrations of metabolites and hormones. Liver was measured for mRNA abundance of 25 candidate genes encoding enzymes and receptors involved in gluconeogenesis (6), fatty acid β-oxidation (6), fatty acid and triglyceride synthesis (5), cholesterol synthesis (4), ketogenesis (2) and the urea cycle (2). Two groups of cows were formed based on the plasma concentrations of glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) (GRP+, high metabolic load; glucose <3.0 mm, NEFA >300 μm and BHBA >1.0 mm, n = 30; GRP-, low metabolic load; glucose >3.0 mm, NEFA <300 μm and BHBA <1.0 mm, n = 30). No differences were found between GRP+ and GRP- for the milk yield at 3 weeks post-partum, but milk fat content was higher (p < 0.01) for GRP+ than for GRP-. In week 8 post-partum, milk yield was higher in GRP+ in relation to GRP- (37.5 vs. 32.5 kg/d; p < 0.01). GRP+ in relation to GRP- had higher (p < 0.001) NEFA and BHBA and lower glucose, insulin, IGF-I, T3 , T4 concentrations (p < 0.01). The mRNA abundance of genes related to gluconeogenesis, fatty acid β-oxidation, fatty acid and triglyceride synthesis, cholesterol synthesis and the urea cycle was different in GRP+ compared to GRP- (p < 0.05), although gene transcripts related to ketogenesis were similar between GRP+ and GRP-. In conclusion, high metabolic load post-partum in dairy cows on-farm corresponds to differences in the liver in relation to dairy cows with low metabolic load, even though all cows were pre-selected for a high milk fat content and fat/protein ratio in milk in their previous lactation.
目的是研究农场中初产奶牛（n = 232）的代谢反应变化，这些奶牛在前一胎次中预先选择了乳脂含量高（>45 g/l）且乳中脂肪/蛋白质比率高（>1.5）。检测血液中代谢物和激素的浓度。检测肝脏中25个候选基因的mRNA丰度，这些基因编码参与糖异生（6个）、脂肪酸β-氧化（6个）、脂肪酸和甘油三酯合成（5个）、胆固醇合成（4个）、生酮作用（2个）和尿素循环（2个）过程的酶和受体。根据葡萄糖、非酯化脂肪酸（NEFA）和β-羟基丁酸（BHBA）的血浆浓度形成两组奶牛（GRP+组；高代谢负荷，葡萄糖<3.0 mmol，NEFA>300 μmol且BHBA>1.0 mmol；n = 30；GRP-组；低代谢负荷，葡萄糖>3.0 mmol，NEFA<300 μmol且BHBA<1.0 mmol；n = 30）。产后3周时，GRP+组和GRP-组的产奶量没有差异，但GRP+组的乳脂含量高于GRP-组（p<0.01）。产后第8周，GRP+组的产奶量高于GRP-组（37.5对32.5 kg/d；p<0.01）。与GRP-组相比，GRP+组的NEFA和BHBA含量更高（p<0.001），而葡萄糖、胰岛素、IGF-I、T3、T4浓度更低（p<0.01）。与GRP-组相比，GRP+组中与糖异生、脂肪酸β-氧化、脂肪酸和甘油三酯合成、胆固醇合成以及尿素循环相关的基因的mRNA丰度存在差异（p<0.05），尽管GRP+组和GRP-组中与生酮作用相关基因的转录本相似。总之，农场中产后高代谢负荷的奶牛与低代谢负荷的奶牛相比，肝脏存在差异即使所有奶牛在前一胎次中都预先选择了高乳脂含量和乳中脂肪/蛋白质比率也如此。
