Department of Dairy and Animal Science, The Pennsylvania State University, University Park, PA 16802, USA.
J Dairy Sci. 2011 Jan;94(1):382-95. doi: 10.3168/jds.2010-3508.
The objectives of this experiment were to investigate the effects of lauric (LA) and myristic (MA) acids on ruminal fermentation, production, and milk fatty acid (FA) profile in lactating dairy cows and to identify the FA responsible for the methanogen-suppressing effect of coconut oil. The experiment was conducted as a replicated 3×3 Latin square. Six ruminally cannulated cows (95±26.4 DIM) were subjected to the following treatments: 240 g/cow per day each of stearic acid (SA, control), LA, or MA. Experimental periods were 28 d and cows were refaunated between periods. Lauric acid reduced protozoal counts in the rumen by 96%, as well as acetate, total VFA, and microbial N outflow from the rumen, compared with SA and MA. Ruminal methane production was not affected by treatment. Dry matter intake was reduced 35% by LA compared with SA and MA, which resulted in decreased milk yield. Milk fat content also was depressed by LA compared with SA and MA. Treatment had no effect on milk protein content. All treatments increased milk concentration of the respective treatment FA. Concentration of C12:0 was more than doubled by LA, and C14:0 was increased (45%) by MA compared with SA. Concentration of milk FA<C16 was 20% lower for LA than MA. Concentrations of trans 18:1 FA (except trans 12) and CLA isomers were increased by LA compared with SA and MA. Overall, the concentrations of saturated FA in milk fat were reduced, and that of >C16 FA and MUFA were increased, by LA compared with the other treatments. In this study, LA had profound effects on ruminal fermentation, mediated through inhibited microbial populations, and decreased DMI, milk yield, and milk fat content. Despite the significant decrease in protozoal counts, however, LA had no effect on ruminal methane production. Thus, the antimethanogenic effect of coconut oil, observed in related studies, is likely due to total FA application level, the additive effect of LA and MA, or a combination of both. Both LA and MA modified milk FA profile significantly.
本实验的目的是研究月桂酸（LA）和肉豆蔻酸（MA）对泌乳奶牛瘤胃发酵、生产性能和乳脂肪酸（FA）谱的影响，并确定椰子油抑制甲烷菌作用的 FA。实验采用 3×3 拉丁方设计进行。6 头瘤胃瘘管奶牛（95±26.4 DIM）接受以下处理：每天每头牛 240 g 的硬脂酸（SA，对照）、LA 或 MA。实验期为 28 天，奶牛在期之间重新接种瘤胃微生物。与 SA 和 MA 相比，LA 使瘤胃原虫数量减少 96%，乙酸、总 VFA 和微生物 N 流出瘤胃的量也减少。处理对瘤胃甲烷产量没有影响。与 SA 和 MA 相比，LA 使干物质采食量降低 35%，导致产奶量下降。LA 还降低了乳脂含量，与 SA 和 MA 相比。处理对乳蛋白含量没有影响。所有处理都增加了各自处理 FA 的牛奶浓度。LA 使 C12:0 浓度增加了一倍以上，MA 使 C14:0 增加了（45%），与 SA 相比。LA 使乳 FA<C16 的浓度比 MA 低 20%。LA 使反式 18:1 FA（除了反式 12）和 CLA 异构体的浓度与 SA 和 MA 相比增加。总体而言，与其他处理相比，LA 降低了乳脂中饱和 FA 的浓度，增加了>C16 FA 和 MUFA 的浓度。在这项研究中，LA 对瘤胃发酵有深远的影响，这是通过抑制微生物种群和减少 DMI、产奶量和乳脂含量来介导的。然而，尽管原虫计数显著减少，但 LA 对瘤胃甲烷产量没有影响。因此，椰子油在相关研究中观察到的抗甲烷作用可能归因于总 FA 应用水平、LA 和 MA 的相加作用或两者的结合。LA 和 MA 都显著改变了乳 FA 谱。
