Although the omasal sampling technique (OST) has been successfully used to estimate ruminal fermentation and nutrient flow, alternatives to invasive animal trials should be pursued and evaluated. The objective of this study was to evaluate carbohydrate and N metabolisms using a meta-analytical approach to compare 2 methods: dual-flow continuous culture system (DFCCS) and OST. To be included, studies needed to report diet chemical composition and report at least 1 of the dependent variables of interest. A total of 155 articles were included, in which 97 used the DFCCS and 58 used the OST. The independent variables used were dietary nonfiber carbohydrate concentration, neutral detergent fiber (NDF) degradability, true crude protein (CP) degradability, and efficiency of microbial protein synthesis (EMPS). In addition, 12 dependent variables were used. Statistical analyses were performed using the Mixed procedure of SAS (SAS Institute Inc., Cary, NC). A random coefficients model was used considering study as a random effect and including the possibility of covariance between the slope and the intercept. The effect of method (DFCCS or OST) was included and tested in the estimates of the intercept, linear, and quadratic effects of the independent variable. There was no method effect when NDF degradability was regressed with total volatile fatty acids concentration, true CP degradability, and EMPS. Molar proportions of acetate and propionate were quadratically associated with NDF degradability. When NDF degradability was regressed with acetate and propionate there was a method effect, differing only in the intercept (β0) estimate. True organic matter digestibility, bacterial N/total N, efficiency of N utilization, total volatile fatty acid concentration, and molar proportion of butyrate linearly increased as dietary nonfiber carbohydrate concentration increased, and none of these variables were affected by method. Concentration of ammonia N had a linear and positive association with true CP degradability. This was the only variable that had a method effect when regressed with true CP degradability, differing only in the estimate of the intercept (β0). As EMPS increased, efficiency of N utilization also increased, and it was affected by method. Overall, the majority of DFCCS responses were similar to OST. When a method effect was observed, it was mainly on the estimate of the intercept, demonstrating that the magnitude of these responses was different. However, the relationships between independent and dependent variables were similar across methods.

中文翻译：

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双流连续培养系统的微生物发酵数据与omasal采样技术的比较：一项荟萃分析方法。

尽管已成功地使用了omasal采样技术（OST）来评估瘤胃发酵和营养流，但仍应寻求和评估侵入性动物试验的替代方法。这项研究的目的是使用荟萃分析方法比较两种方法：双流连续培养系统（DFCCS）和OST来评估碳水化合物和N的代谢。要纳入研究，必须报告饮食化学成分并报告至少1个相关因变量。总共包括155条文章，其中97条使用DFCCS，58条使用OST。所使用的自变量是膳食中非纤维碳水化合物的浓度，中性洗涤剂纤维（NDF）的可降解性，真实粗蛋白（CP）的可降解性以及微生物蛋白合成的效率（EMPS）。另外，使用了12个因变量。使用SAS的混合程序（SAS Institute Inc.，北卡罗来纳州卡里）进行统计分析。使用随机系数模型将研究视为随机效应，并包括斜率和截距之间的协方差可能性。方法的效果（DFCCS或OST）已包括在内，并在估计自变量的截距，线性和二次方影响中进行了测试。当NDF降解性与总挥发性脂肪酸浓度，真实CP降解性和EMPS回归时，没有方法效果。摩尔比例的乙酸盐和丙酸盐与NDF降解能力呈二次关系。当用乙酸盐和丙酸盐降解NDF的可降解性时，会产生方法效果，仅在截距（β0）估计上有所不同。真正的有机物消化率，细菌氮/总氮，氮的利用效率，总挥发性脂肪酸浓度和丁酸酯的摩尔比例随膳食非纤维碳水化合物浓度的增加而线性增加，并且这些变量均不受方法影响。氨氮的浓度与真正的CP降解能力呈线性正相关。这是唯一具有真正CP降解能力回归时具有方法效果的变量，仅在截距（β0）的估计上有所不同。随着EMPS的增加，氮的利用效率也增加，并且受到方法的影响。总体而言，大多数DFCCS响应与OST类似。观察到方法效果时，主要取决于截距的估计，表明这些响应的大小不同。然而，