College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, Henan 450046, People's Republic of China.
Modern Experimental Technique and Management Centre, Henan Agricultural University, Zhengzhou, Henan 450002, People's Republic of China.
J Dairy Sci. 2021 Jul;104(7):8301-8313. doi: 10.3168/jds.2020-19679. Epub 2021 Apr 15.
Metabolism in most organisms can show variations between the day and night. These variations may also affect the composition of products derived from livestock. The aim of the present study was to investigate the difference in composition between the day milk and night milk of dairy cows. Ten multiparous Holstein cows (milk yield = 25.2 ± 5.00 kg/d) were randomly selected during mid lactation. Milk samples were collected at 0500 h ("night milk") and 1500 h ("day milk") and analyzed to determine their composition. Mid-infrared spectroscopy was used to analyze macronutrient content of milk. Metabolomics and lipidomics were used to detect and analyze small molecules and fatty acids, respectively. An automatic biochemical analyzer and ELISA kits were used to determine biochemical indicators, as well as antioxidant and immune parameters in the milk. Though milk fat, protein, lactose, and total milk solids were not different between day milk and night milk, small molecules, metabolites and lipids, and hormones and cytokines differed between day milk and night milk. Regarding biochemical and immune-related indicators, the concentrations of malondialdehyde, HSP70, and HSP90 in night milk were lower than that in day milk. However, interferon-γ levels were higher in night milk. Additionally, night milk was naturally rich in melatonin. Lipidomics analyses showed that the levels of some lipids in night milk were higher than those in day milk. Metabolomics analyses identified 36 different metabolites between day milk and night milk. Higher concentrations of N-acetyl-d-glucosamine, cis-aconitate, and d-sorbitol were observed in day milk. However, the other 33 metabolites analyzed, including carbohydrates, lipids, AA, and aromatic compounds, showed lower concentrations in day milk than in night milk. The present findings show that the composition of night milk differs considerably from that of day milk. Notable changes in the circadian rhythm also altered milk composition. These results provide evidence to support the strategic use and classification of day milk and night milk.
大多数生物体的新陈代谢在白天和黑夜之间会发生变化。这些变化也可能影响来自家畜的产品的组成。本研究的目的是研究奶牛白天奶和夜间奶之间的组成差异。在泌乳中期，随机选择了 10 头经产荷斯坦奶牛（产奶量=25.2±5.00kg/d）。分别于 05:00 时（“夜间奶”）和 15:00 时（“白天奶”）采集奶样，并进行分析以确定其组成。中红外光谱用于分析奶中宏量营养素含量。代谢组学和脂质组学分别用于检测和分析小分子和脂肪酸。自动生化分析仪和 ELISA 试剂盒用于测定奶中的生化指标以及抗氧化和免疫参数。尽管白天奶和夜间奶的乳脂、蛋白质、乳糖和总乳固体没有差异，但小分子、代谢物和脂质、激素和细胞因子在白天奶和夜间奶之间存在差异。关于生化和免疫相关指标，夜间奶中的丙二醛、HSP70 和 HSP90 的浓度低于白天奶。然而，夜间奶中的干扰素-γ水平较高。此外，夜间奶中天然富含褪黑素。脂质组学分析表明，夜间奶中某些脂质的水平高于白天奶。代谢组学分析在白天奶和夜间奶之间鉴定出 36 种不同的代谢物。白天奶中观察到 N-乙酰-d-葡萄糖胺、顺乌头酸和 d-山梨醇的浓度较高。然而，分析的其他 33 种代谢物，包括碳水化合物、脂质、AA 和芳香族化合物，在白天奶中的浓度低于夜间奶。本研究结果表明，夜间奶的组成与白天奶有很大差异。昼夜节律的显著变化也改变了奶的组成。这些结果为支持白天奶和夜间奶的战略使用和分类提供了证据。
