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首页> 外文期刊>Journal of dairy science >A model of ruminal volatile fatty acid absorption kinetics and rumen epithelial blood flow in lactating Holstein cows
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A model of ruminal volatile fatty acid absorption kinetics and rumen epithelial blood flow in lactating Holstein cows

机译：泌乳荷斯坦奶牛瘤胃挥发性脂肪酸吸收动力学和瘤胃上皮血流的模型

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摘要

Ruminal absorption of volatile fatty acids (VFA) is quantitatively the most important nutrient flux in cattle. Historically, VFA absorption models have been derived primarily from ruminal variables such as chemical composition of the fluid, volume, and pH. Recently, a mechanistic model incorporated the control of VFA absorption from epithelial surface area of the reticulorumen. In the present study, we hypothesized that ruminal absorption of VFA was controlled through epithelial permeability to VFA and rumen epithelial capillary blood flow. The objective of the study was to construct a model of VFA exchange across the rumen wall that incorporates epithelial blood flow as a driv-ing force for ruminal VFA removal. The bidirectional fluxes between the ruminal and epithelial pool of VFA were assumed mass action driven, given that passive diffusion of nonionized VFA is the dominant transmem-brane VFA flux. Parameter estimates were derived by fitting the model to observed data. The model provided reliable unbiased estimates of ruminal VFA absorp-tion and rumen epithelial blood flow. Blood flow was modeled using an equation that considered the effect of butyrate and dietary crude protein intake per kilo-gram of body weight. The rate constants related to the flux from ruminal fluid to epithelium were in the order isobutyrate < acetate < propionate < butyrate (0.32 ± 0.02, 0.72 ± 0.2, 0.91 ± 0.06, and 0.97 ± 0.02 /h, respectively). The rate constants for fluxes of isobutyr-ate, acetate, propionate, and butyrate from the rumen epithelium to the ruminal fluid, relative to the pool size of the epithelium, were 4.78, 10.6, 13.4, and 14.3 /h, respectively. Ruminal concentrations of acetate, pro-pionate, butyrate, and isobutyrate were predicted with root mean square prediction errors as percentage of the observed means (RMSPE) of 5.86, 5.75, 11.3, and 4.12, respectively. The epithelial blood flow was predicted with 26.3% RMSPE. Sensitivity analyses indicated that when ruminal butyrate concentration increased from 4.0 to 37.4 mmol/L, blood flow of the epithelium increased 47% and the ruminal disappearance rate of propionate increased 11%. The concentration gradient of propionate between ruminal fluid and epithelium was no more than 3:1 and increased with increasing blood flow. In conclusion, a dynamic model based on rumen epithelial blood flow and bidirectional fluxes of VFA between ruminal fluid and epithelium gave unbi-ased predictions with low residual error of ruminal VFA absorption under washed rumen conditions. The model indicates that the effect of varying epithelial blood flow on the control of ruminal VFA absorption is related to the concentration gradient of individual VFA between ruminal fluid and epithelial blood. Epithelial blood flow may be an important determinant of ruminal absorp-tion of VFA, a result that has not been evaluated on independent data.
机译：从数量上来说，瘤胃对挥发性脂肪酸（VFA）的吸收是牛中最重要的营养通量。从历史上看，VFA吸收模型主要来自瘤胃变量，例如液体的化学成分，体积和pH。最近，一种机械模型结合了对网状上皮表面积VFA吸收的控制。在本研究中，我们假设VFA的瘤胃吸收是通过VFA的上皮通透性和瘤胃上皮毛细血管血流来控制的。该研究的目的是构建跨瘤胃壁的VFA交换模型，该模型结合了上皮血流作为瘤胃VFA去除的推动力。假定非离子化VFA的被动扩散是主要的跨膜VFA通量，VFA的瘤胃和上皮池之间的双向通量被认为是质量作用驱动的。通过将模型拟合到观测数据，可以得出参数估计值。该模型提供了可靠的瘤胃VFA吸收和瘤胃上皮血流的无偏估计。使用考虑了每公斤体重丁酸和膳食粗蛋白摄入量影响的方程式对血流进行建模。与从瘤胃液到上皮的通量有关的速率常数为异丁酸酯<乙酸酯<丙酸酯<丁酸酯（分别为0.32±0.02、0.72±0.2、0.91±0.06和0.97±0.02 / h）。从瘤胃上皮到瘤胃液的异丁酸，乙酸，丙酸和丁酸通量的速率常数相对于上皮池大小分别为4.78、10.6、13.4和14.3 / h。预测乙酸盐，丙酸酯，丁酸酯和异丁酸酯的瘤胃浓度，均方根预测误差分别为观察到的均值（RMSPE）的百分比，分别为5.86、5.75、11.3和4.12。预测上皮血流量为26.3％RMSPE。敏感性分析表明，当瘤胃丁酸浓度从4.0增加到37.4 mmol / L时，上皮的血流量增加47％，丙酸瘤胃消失率增加11％。瘤胃液和上皮之间的丙酸盐浓度梯度不超过3：1，并且随着血流量的增加而增加。总之，基于瘤胃上皮血流和瘤胃液与上皮之间的VFA双向通量的动力学模型给出了不偏不倚的预测，在冲洗瘤胃条件下瘤胃VFA吸收的残留误差低。该模型表明，上皮血流量的变化对瘤胃VFA吸收控制的影响与瘤胃液和上皮血之间各个VFA的浓度梯度有关。上皮血流可能是瘤胃吸收VFA的重要决定因素，这一结果尚未根据独立数据进行评估。

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  • 来源
    《Journal of dairy science》 |2012年第6期|p.2919-2934|共16页
  • 作者

    A. C. Storm; N. B. Kristensen; M. D. Hanigarn;

  • 作者单位

    Department of Animal Health and Bioscience, Faculty of Agricultural Sciences, Aarhus University, DK-8830 Tjele, Denmark;

    Department of Animal Health and Bioscience, Faculty of Agricultural Sciences, Aarhus University, DK-8830 Tjele, Denmark;

    Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061;

  • 收录信息 美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    dairy cow; volatile fatty acid model; epithelium blood flow; ruminal volatile fatty acid kinetics;

    机译：奶牛;挥发性脂肪酸模型上皮血流瘤胃挥发性脂肪酸动力学;

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