Precalving feeding level and body condition score (BCS) alter postcalving energy balance and oxidant status of dairy cows. We hypothesized that the reported benefits of a controlled restriction precalving depend on precalving BCS. The objective was to identify alterations in activity and intermediates of the hepatic one-carbon metabolism, transsulfuration, and tricarboxylic acid pathways. Twenty-eight pregnant and nonlactating grazing dairy cows of mixed age and breed (Friesian, Friesian × Jersey) were randomly allocated to 1 of 4 treatment groups in a 2 × 2 factorial design: 2 prepartum BCS categories [4.0 (thin, BCS4) and 5.0 (optimal, BCS5); 10-point scale], by managing cows in late lactation to achieve the 2 groups at dry-off, and 2 levels of energy intake during the 3 wk preceding calving (75 or 125% of estimated requirements), obtained via allowance (m2/cow) of fresh pasture composed of mostly perennial ryegrass and white cover. Average (± standard deviation) age was 6 ± 2, 6 ± 3, 5 ± 1, and 7 ± 3 yr for BCS4 fed 75 and 125%, and BCS5 fed 75 and 125%, respectively. Breed distribution (average ± standard deviation) for the 4 groups was 79 ± 21, 92 ± 11, 87 ± 31, and 74 ± 23% Friesian, and 17 ± 20, 8 ± 11, 13 ± 31, and 25 ± 23% Jersey. Liver tissue was collected by biopsy at -7, 7, and 28 d relative to calving. Tissue was used for 14C radio-labeling assays to measure betaine-homocysteine S-methyltransferase, 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), and cystathionine-β-synthase (CBS) activity. Liver metabolomics was undertaken using a targeted liquid chromatography with tandem mass spectrometry-based profiling approach. After initial liquid chromatography separation, mass spectra were acquired under both positive and negative ionization, whereas multiple reaction monitoring was used to measure target compound signal response (peak area count). Enzyme activity and metabolite peak area count were normalized with the homogenate protein concentration. Repeated measures analysis of variance via PROC MIXED in SAS (SAS Institute Inc., Cary, NC), with BCS, feeding, and time as fixed effects, and cow as random effect was used. All enzyme activities were affected by time, with betaine-homocysteine S-methyltransferase activity peaking at 7 d, whereas CBS and MTR activity decreased postpartum. Overall, thin cows had greater MTR activity, whereas cows fed 125% requirements had greater CBS activity. An interaction was detected between BCS and feeding for CBS activity, as thin cows fed 125% of requirements had greater overall activity. Compared with liver from BCS4 cows, BCS5 cows had overall greater betaine, glycine, butyrobetaine/acetylcholine, serine, and taurine concentrations. The same metabolites, plus choline and N-N-dimethylglycine, were overall greater in liver of cows fed 75% compared with those fed 125% of requirements. An interaction of BCS and feeding level was detected for the aforementioned metabolites plus methionine, cystathionine, cysteinesulfinate, and hypotaurine, due to greater overall concentrations in BCS5 cows fed 75% of requirements compared with other groups. Overall, differences in hepatic enzyme activity and intermediate metabolites suggest that both BCS and feeding level can alter the internal antioxidant system (e.g., glutathione and taurine) throughout the periparturient period. Further studies are needed to better understand potential mechanisms involved.

中文翻译：

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放牧的荷斯坦奶牛的肝一碳代谢酶活性和中间代谢物会因产前身体状况评分和营养面而改变。

产犊前的摄食水平和身体状况评分（BCS）会改变产犊后产犊的能量平衡和氧化剂状态。我们假设，控制限制产犊前报道的益处取决于产犊前BCS。目的是确定肝一碳代谢，转硫和三羧酸途径的活性和中间体的变化。在2×2因子设计中，将28个不同年龄和品种（弗里斯兰，弗里斯兰×泽西岛）的怀孕和不哺乳放牧奶牛随机分配到4个治疗组中的1个：2个产前BCS类别[4.0（瘦，BCS4）和5.0（最佳，BCS5）；[10分制]，通过控制泌乳后期的母牛达到干dry状态下的两组，以及在产犊前3周内达到2个能量摄入水平（估计需求量的75％或125％），通过以大部分多年生黑麦草和白色覆盖物组成的新鲜牧场的配额（平方米/牛）获得的。BCS4喂食75和125％，BCS5喂食75和125％的平均年龄（±标准偏差）分别为6±2、6±3、5±1和7±3岁。4组的品种分布（平均±标准偏差）分别为79±21、92±11、87±31和74±23％弗里斯兰，以及17±20、8±11、13±31和25±23％球衣。相对于产犊，在-7、7和28天通过活检收集肝组织。将组织用于14C放射性标记测定，以测量甜菜碱-高半胱氨酸S-甲基转移酶，5-甲基四氢叶酸-高半胱氨酸甲基转移酶（MTR）和胱硫醚-β-合酶（CBS）活性。使用靶向液相色谱和基于串联质谱的分析方法进行肝脏代谢组学。最初的液相色谱分离后，在正电离和负电离下均获得质谱，而多反应监测用于测量目标化合物的信号响应（峰面积计数）。酶活性和代谢物峰面积计数用匀浆蛋白浓度标准化。通过在SAS（SAS Institute Inc.，Cary，NC）中通过PROC MIXED进行的方差重复测量分析，以BCS，喂养和时间为固定效应，以牛为随机效应。所有酶活性均受时间影响，甜菜碱-高半胱氨酸S-甲基转移酶活性在7 d达到峰值，而产后CBS和MTR活性降低。总体而言，瘦母牛的MTR活性更高，而满足125％需求的母牛的CBS活性更高。在BCS和饲喂之间发现了CBS活性之间的相互作用，因为饲喂满足需求量125％的瘦奶牛的总体活动能力更高。与BCS4牛的肝脏相比，BCS5牛的总体甜菜碱，甘氨酸，丁甜菜碱/乙酰胆碱，丝氨酸和牛磺酸的浓度更高。饲喂75％的母牛肝脏中相同的代谢产物，加上胆碱和NN-二甲基甘氨酸，总体上高于饲喂125％需求量的母牛。检测到上述代谢物加蛋氨酸，胱硫醚，半胱氨酸亚磺酸盐和次牛磺酸的BCS与饲喂水平之间存在相互作用，这是因为与其他组相比，饲喂75％需求量的BCS5奶牛的总体浓度更高。总体而言，肝酶活性和中间代谢产物的差异表明，整个围产期，BCS和摄食水平均可以改变内部抗氧化系统（例如谷胱甘肽和牛磺酸）。