Laboratory for Animal Nutrition and Animal Product Quality, Ghent University, Proefhoevestraat 10, 9090 Melle, Belgium.
J Dairy Sci. 2010 Oct;93(10):4759-73. doi: 10.3168/jds.2010-3158.
High-concentrate diets can lead to subacute ruminal acidosis and are known to result in changes of the ruminal fermentation pattern and mammary secretion of fatty acids. The objective of this paper is to describe modifications in milk fatty acid proportions, particularly odd- and branched-chain fatty acids and rumen biohydrogenation intermediates, associated with rumen parameters during a 6-wk subacute ruminal acidosis induction protocol with 12 ruminally fistulated multiparous cows. The protocol involved a weekly gradual replacement of a standard dairy concentrate with a wheat-based concentrate (610 g of wheat/kg of concentrate) during the first 5 wk and an increase in the total amount of concentrate in wk 6. Before the end of induction wk 6, cows were switched to a control diet because 7 cows showed signs of sickness. The pH was measured continuously by an indwelling pH probe. Milk and rumen samples were taken on d 2 and 7 of each week. Data were analyzed using a linear mixed model and by principal component analysis. A pH decrease occurred after the first concentrate switch but rumen parameters returned to the original values and remained stable until wk 5. In wk 5 and 6, rumen pH values were indicative of increasing acidotic conditions. After switching to the control diet in wk 6, rumen pH values rapidly achieved normal values. Odd- and branched-chain fatty acids and C18:1 trans-10 increased with increasing amount of concentrate in the diet, whereas C18:1 trans-11 decreased. Four fatty acids [C18:1 trans-10, C15:0 and C17:0+C17:1 cis-9 (negative loadings), and iso C14:0 (positive loading)] largely correlated with the first principal component (PC1), with cows spread along the PC1 axis. The first 4 wk of the induction experiment showed variation across the second principal component (PC2) only, with high loadings of anteiso C13:0 (negative loading) and C18:2 cis-9,trans-11 and C18:1 trans-11 (positive loadings). Weeks 5 and 6 deviated from PC2 and tended toward the negative PC1 axis. A discriminant analysis using a stepwise approach indicated the main fatty acids discriminating between the control and acidotic samples as iso C13:0, iso C16:0, and C18:2 cis-9,trans-11 rather than milk fat content or C18:1 trans-10, which have been used before as indicators of acidosis. This shows that specific milk fatty acids have potential in discriminating acidotic cases.
高浓度日粮可导致亚急性瘤胃酸中毒，并已知会导致瘤胃发酵模式和乳脂脂肪酸组成发生变化。本文的目的是描述在 12 头瘤胃瘘管的经产奶牛中，用 6 周的亚急性瘤胃酸中毒诱导方案中，与瘤胃参数相关的乳脂肪酸比例变化，特别是奇数和支链脂肪酸和瘤胃生物氢化中间产物。该方案涉及在第 1 到 5 周内每周逐渐用基于小麦的浓缩物（每千克浓缩物 610 克小麦）替代标准奶牛浓缩物，第 6 周增加浓缩物总量。在第 6 周诱导结束之前，因为 7 头牛出现疾病迹象，所以奶牛切换到对照饮食。通过内置 pH 探头连续测量 pH。每周第 2 天和第 7 天采集牛奶和瘤胃液样本。使用线性混合模型和主成分分析对数据进行分析。第一次更换浓缩物后 pH 下降，但瘤胃参数恢复到原始值并保持稳定，直到第 5 周。在第 5 和第 6 周，瘤胃 pH 值表明酸中毒条件增加。第 6 周切换到对照饮食后，瘤胃 pH 值迅速恢复正常。随着日粮中浓缩物含量的增加，奇数和支链脂肪酸以及 C18:1 trans-10 增加，而 C18:1 trans-11 减少。有 4 种脂肪酸 [C18:1 trans-10、C15:0 和 C17:0+C17:1 cis-9（负负荷）和 iso C14:0（正负荷）] 与第一主成分（PC1）密切相关，奶牛沿着 PC1 轴分布。诱导实验的前 4 周仅在第二个主成分（PC2）上显示出变化，高负载的 anteiso C13:0（负负荷）和 C18:2 cis-9，trans-11 和 C18:1 trans-11（正负荷）。第 5 和第 6 周偏离 PC2 并倾向于负 PC1 轴。使用逐步方法的判别分析表明，区分对照和酸中毒样本的主要脂肪酸是 iso C13:0、iso C16:0 和 C18:2 cis-9，trans-11，而不是乳脂含量或 C18:1 trans-10，以前曾用作酸中毒的指标。这表明特定的乳脂肪酸具有区分酸中毒病例的潜力。
