Supplementing palmitic acid (C16 : 0) in combination with modifying the dietary n-6:n-3 fatty acid (FA) ratio may benefit energy metabolism and milk responses of dairy cows. Twelve Holstein cows (70 (sd 11) days in milk) were used in a replicated 4 × 4 Latin square and allocated to four low-fibre diets (18·5 % forage neutral-detergent fibre) supplemented with no FA (CON), or 2·4 % C16 : 0-enriched supplement (PAL), 2·4 % mixture (2:1) of C16 : 0 and n-6 FA (PW6), and mixture (2:1) of C16 : 0 and n-3 FA (PW3). The dietary ratio of n-6:n-3 was increased with PW6 (10:1) and decreased with PW3 (2·8:1), whereas PAL alone made no change in the ratio (about 7:1). Compared with CON, all FA-supplemented treatments increased milk yield. However, feed and energy intakes were higher in PAL than PW3 or PW6, resulting in greater feed efficiency for PW3 and PW6 than PAL. Dietary FA supplements decreased milk protein concentration but tended to increase protein yield. Compared with CON and FA mixtures, PAL increased milk fat content and tended to increase milk SFA and atherosclerotic index. The concentration of milk n-3 FA was similar between CON and PW3. Feeding PAL increased milk energy output and decreased energy partitioning towards body reserves (−4·2 %), while this measure was positive for other treatments. Blood TAG and NEFA concentrations, but not β-hydroxybutyrate, were increased by FA-supplemented treatments. Feeding C16 : 0 combined with either n-6 or n-3 FA enhanced feed efficiency, alleviated the negative impacts on body energy reserves, but lowering the dietary n-6:n-3 ratio improved the FA profile of milk.

中文翻译：

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补充棕榈酸和改变低纤维日粮中n-6:n-3脂肪酸的日粮比例对奶牛生产反应的影响

补充棕榈酸 (C16 : 0) 与改变饮食相结合n-6：n-3 脂肪酸 (FA) 比例可能有利于奶牛的能量代谢和牛奶反应。十二头荷斯坦奶牛（70 (sd11) 天牛奶）用于重复的 4 × 4 拉丁方格，并分配给四种低纤维日粮（18·5 % 牧草中性洗涤剂纤维），不含 FA (CON) 或 2·4 % C16： 0 浓缩补充剂 (PAL)、2·4 % 混合物 (2:1) C16 : 0 和n-6 FA (PW6) 和 C16 的混合物 (2:1) : 0 和n-3 FA (PW3)。膳食比例为n-6：n-3 随 PW6 (10:1) 增加而随 PW3 (2·8:1) 减少，而单独使用 PAL 的比例没有变化（约 7:1）。与 CON 相比，所有补充 FA 的处理均增加了产奶量。然而，PAL 的饲料和能量摄入量高于 PW3 或 PW6，导致 PW3 和 PW6 的饲料效率高于 PAL。膳食 FA 补充剂降低了乳蛋白浓度，但倾向于增加蛋白质产量。与 CON 和 FA 混合物相比，PAL 增加了乳脂肪含量，并倾向于增加乳 SFA 和动脉粥样硬化指数。牛奶的浓度n-3 FA 在 CON 和 PW3 之间相似。喂养 PAL 增加了牛奶能量输出并减少了能量分配到身体储备 (-4·2 %)，而这一措施对其他治疗是积极的。血液 TAG 和 NEFA 浓度，但不是β-羟基丁酸，通过补充 FA 的处理增加。进料 C16 : 0 与任一n-6 或n-3 FA 提高了饲料效率，减轻了对身体能量储备的负面影响，但降低了日粮n-6：n-3 比例改善了牛奶的 FA 谱。