Bitman J, Wood D L
Livestock and Poultry Sciences Institute, US Department of Agriculture, Beltsville, MD 20705.
J Dairy Sci. 1990 May;73(5):1208-16. doi: 10.3168/jds.S0022-0302(90)78784-X.
Changes in lipid composition were studied in milk obtained on postpartum d 3 (colostrum), 7, 42, and 180 from 12 Holstein cows. Triglycerides, 96 to 97% of total lipids, were relatively constant during lactation. Phospholipids and cholesterol declined with advancing lactation. Concentrations of the fatty acids synthesized within the mammary gland, C10:0 to C16:0, increased about 50% from 7 to 42 d of lactation. During this period, compensatory decreases were observed in C18:1. The phospholipids were separated into five major classes: sphingomyelin, phosphatidyl choline, serine, inositol, and ethanolamine for fatty acid analysis. The changes that occurred in milk total fatty acids were reflected in phosphatidyl phospholipid fatty acid composition: an increase in medium-chain fatty acids and a decrease in polyunsaturated fatty acids of 18, 20, and 22 carbon atom chain length as lactation progressed. These changes are consistent with the theory that milk phospholipids are synthesized de novo entirely in the mammary gland.
对12头荷斯坦奶牛产后第3天（初乳）、第7天、第42天和第180天采集的牛奶中的脂质成分变化进行了研究。甘油三酯占总脂质的96%至97%，在泌乳期间相对稳定。磷脂和胆固醇随着泌乳进程而下降。乳腺内合成的脂肪酸（C10:0至C16:0）的浓度在泌乳第7天至42天期间增加了约50%。在此期间，观察到C18:1出现代偿性下降。磷脂被分为五大类：鞘磷脂、磷脂酰胆碱、丝氨酸、肌醇和乙醇胺，用于脂肪酸分析。牛奶总脂肪酸中发生的变化反映在磷脂酰磷脂脂肪酸组成中：随着泌乳的进行，中链脂肪酸增加，碳链长度为18、20和22的多不饱和脂肪酸减少。这些变化与牛奶磷脂完全在乳腺中从头合成的理论一致。
