Department of Animal Health and Bioscience, Faculty of Agricultural Sciences, Aarhus University, DK-8830 Tjele, Denmark.
J Dairy Sci. 2011 Aug;94(8):3980-94. doi: 10.3168/jds.2010-4091.
The effect of reticuloruminal epithelial blood flow on the absorption of propionate as a volatile fatty acid (VFA) marker in 8 lactating Holstein cows was studied under washed rumen conditions. The cows were surgically prepared with ruminal cannulas and permanent catheters in an artery and mesenteric, right ruminal, and hepatic portal veins. The experiment was designed with 2 groups of cows: 4 cows adapted to high crude protein (CP) and 4 to low CP. All cows were subjected to 3 buffers: butyric, ammonia, and control in a randomized replicated 3 × 3 incomplete Latin square design. The buffers (30 kg) were maintained in a temporarily emptied and washed rumen for 40 min. The initial concentration of VFA was 84.2 mmol/L. Butyrate was increased from 4 to 36 mmol/L in butyric buffer by replacement of acetate, and ammonia (NH(3)) was increased from 2.5 to 22.5 mmol/L in ammonia buffer by replacement of NaCl. Increasing amounts of deuterium oxide (D(2)O) were added to the buffers as the order of buffer sequence increased (6, 12, and 18 g of D(2)O). Ruminal clearance of D(2)O was used to estimate epithelial blood flow. To increase accuracy of the epithelial blood flow estimates, data of ruminal liquid marker (Cr-EDTA), and initial and final buffer volumes were fitted to a dynamic simulation model. The model was used to estimate ruminal liquid passages, residual liquid, and water influx (saliva and epithelia water) for each combination of cow and buffer (n=24). Epithelial blood flow increased 49±11% for butyric buffer compared with control. The ruminal disappearance of propionate (marker VFA) was affected by buffer and followed the same pattern as for epithelial blood flow. The correlation between ruminal disappearance of propionate and epithelial blood flow (r=0.56) indicates that the removal of propionate can be limited by epithelial blood flow. The ruminal disappearance of propionate increased 30±12% for the butyric compared with ammonia buffer and 12.5±8% when compared with control. The net portal flux of propionate increased 32±6% in butyric compared with control. In conclusion, rumen epithelial blood flow is positively correlated with ruminal disappearance of propionate and affects the kinetics of ruminal VFA absorption.
在绵羊瘤胃被清洗的条件下，研究了反刍动物的黏膜血流对丙酸（一种挥发性脂肪酸（VFA））作为挥发性脂肪酸（VFA）标记物吸收的影响。在接受手术的荷斯坦奶牛的瘤胃中，使用了瘤胃套管和永久性动脉、肠系膜、右瘤胃和肝门静脉的导管。该实验采用两组奶牛：4 头适应高蛋白（CP），4 头适应低蛋白。所有奶牛都接受了 3 种缓冲液：丁酸、氨和对照，随机重复 3×3 不完全拉丁方设计。缓冲液（30kg）在暂时排空和清洗的瘤胃中维持 40 分钟。初始 VFA 浓度为 84.2mmol/L。丁酸缓冲液中通过乙酸盐的替代，将丁酸的浓度从 4mmol/L 提高到 36mmol/L，氨缓冲液中通过 NaCl 的替代，将氨（NH3）的浓度从 2.5mmol/L 提高到 22.5mmol/L。随着缓冲液顺序的增加，向缓冲液中添加越来越多的重水（D2O）（6、12 和 18g 的 D2O）。使用瘤胃液中重水（D2O）的清除率来估计黏膜血流。为了提高黏膜血流估计的准确性，对瘤胃液示踪剂（Cr-EDTA）的数据和初始及最终缓冲液体积进行了拟合，以适应动态模拟模型。该模型用于估计每头奶牛和每一种缓冲液的组合的瘤胃液体交换、残留液体和水的流入（唾液和黏膜水）（n=24）。与对照相比，丁酸缓冲液使黏膜血流增加了 49±11%。丙酸（标记 VFA）在瘤胃中的消失受到缓冲液的影响，并遵循与黏膜血流相同的模式。丙酸在瘤胃中的消失与黏膜血流（r=0.56）之间的相关性表明，丙酸的去除可能受到黏膜血流的限制。与氨缓冲液相比，丁酸缓冲液使丙酸在瘤胃中的消失增加了 30±12%，与对照相比增加了 12.5±8%。丙酸的门静脉净流量在丁酸中比在对照中增加了 32±6%。总之，瘤胃黏膜血流与丙酸在瘤胃中的消失呈正相关，并影响瘤胃 VFA 吸收的动力学。
